ICS 85.080.01  
 
Reference number
DRS 554: 2023
© RSB 2023
  
 RWANDA 
STANDARD  DRS 
554 
 
Firstedition  
2023-mm-dd 
 
Painting of buildings— Code of practice  
   
DRS 554: 2023 
©RSB 2023- All rights reserved                  ii 
 In order to match with technological development and to keep continuous progress in industries, 
standards are subject to periodic review. Users shall ascertain that they are in possession of the latest 
edition 
 
 
 
 
 
 
 
 
© RSB2023 
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized 
in any form or by any means, electronic or mechanical, including photocopying and microfilm, without 
prior written permission from RSB. 
Requests for permission to reproduce this document should be addressed to: 
Rwanda Standards Board 
P.O Box 7099 Kigali-Rwanda 
KK 15 Rd, 49 
Tel. +250 788303492 
Toll Free: 3250 
E-mail: info@rsb.gov.rw  
Website: www.rsb.gov.rw  
ePortal: www.portal.rsb.gov.rw  DRS 554: 2023 
iii                ©RSB2023- All rights reserved 
 Contents Page 
Foreword ............................................................................................................................................................ ix  
1 Scope ...................................................................................................................................................... 1  
2 Normative references ............................................................................................................................ 1  
3 Terms and definitions ......................................................................................................................... 32 
4 Design considerations ........................................................................................................................ 42 
4.1 General ................................................................................................................................................. 42 
4.2 Accessibility ......................................................................................................................................... 43 
4.3 Control of moisture ............................................................................................................................. 43 
4.4 Profiles ................................................................................................................................................. 54 
4.5 Selection of materials ......................................................................................................................... 54 
4.5.1 General ................................................................................................................................................. 54 
4.5.2 Volatile organic compounds .............................................................................................................. 54 
4.6 Selection of coating systems ............................................................................................................. 54 
4.6.1 General ................................................................................................................................................. 54 
4.6.2 Exposure conditions ........................................................................................................................... 65 
4.6.3 Substrates and coating systems ....................................................................................................... 65 
4.6.4 Special conditions and requirements ............................................................................................... 75 
5 Organization of work ........................................................................................................................... 29  
5.1 General ................................................................................................................................................. 29  
5.2 Health and safety ................................................................................................................................. 30  
5.3 Order of working .................................................................................................................................. 30  
5.4 Scaffolding and equipment ................................................................................................................ 30  
5.5 Supply of materials ............................................................................................................................. 31  
5.6 Storage of materials ............................................................................................................................ 31  
5.7 Protection of components on site ..................................................................................................... 31  
5.7.1 General ................................................................................................................................................. 31  
5.7.2 Joinery .................................................................................................................................................. 32  
5.7.3 Metal components ............................................................................................................................... 32  
5.7.4 Structural steel members ................................................................................................................... 32  
5.8 Off-site work ......................................................................................................................................... 32  
5.9 Workforce and supervision ................................................................................................................ 32  
5.10 Inspection and supervision ................................................................................................................ 33  
5.11 Materials sampling and testing .......................................................................................................... 33  
6 Exchange of information .................................................................................................................... 33  
6.1 General ................................................................................................................................................. 33  
6.2 Specification ........................................................................................................................................ 33  
6.2.1 General ................................................................................................................................................. 33  
6.2.2 Surface preparation ............................................................................................................................. 34  
6.2.3 Coating system materials ................................................................................................................... 34  
6.2.4 Application ........................................................................................................................................... 34  
6.2.5 Inspection procedure .......................................................................................................................... 34  
6.3 Bills of quantities ................................................................................................................................. 35  
6.4 Schedules ............................................................................................................................................. 35  
6.5 Drawings .............................................................................................................................................. 35  
6.6 Records ................................................................................................................................................ 35  
7 Materials ............................................................................................................................................... 35  
7.1 Functions of coatings ......................................................................................................................... 35  DRS 554: 2023 
©RSB 2023- All rights reserved                  iv 
 7.1.1 General ................................................................................................................................................. 35  
7.1.2 Protection by coating systems .......................................................................................................... 36  
7.1.3 Decoration ........................................................................................................................................... 36  
7.1.4 Hygiene ................................................................................................................................................ 36  
7.1.5 Special functions ................................................................................................................................ 36  
7.2 General properties of coatings .......................................................................................................... 36  
7.2.1 General ................................................................................................................................................. 36  
7.2.2 Viscosity .............................................................................................................................................. 37  
7.2.3 Flow ...................................................................................................................................................... 37  
7.2.4 Film thickness ..................................................................................................................................... 37  
7.3 Components of coating systems ...................................................................................................... 37  
7.3.1 General ................................................................................................................................................. 37  
7.3.2 Primers and sealers ............................................................................................................................ 38  
7.3.3 Undercoats .......................................................................................................................................... 38  
7.3.4 Finishes ............................................................................................................................................... 39  
7.3.5 Compatibility of coatings ................................................................................................................... 39  
7.4 Ancillary materials .............................................................................................................................. 39  
7.4.1 Cleaning agents .................................................................................................................................. 39  
7.4.2 Sterilizing washes ............................................................................................................................... 39  
7.4.3 Knotting ............................................................................................................................................... 40  
7.4.4 Stoppers and fillers ............................................................................................................................ 40  
7.4.5 Mastics and sealants .......................................................................................................................... 41  
7.4.6 Water repellents .................................................................................................................................. 41  
8 Substrates and coating systems ....................................................................................................... 41  
8.1 Wood .................................................................................................................................................... 41  
8.1.1 Extractive ............................................................................................................................................. 41  
8.1.2 Moisture content ................................................................................................................................. 42  
8.1.3 Penetration of binder .......................................................................................................................... 42  
8.1.4 External influences ............................................................................................................................. 42  
8.1.5 Preservative treatments ..................................................................................................................... 43  
8.1.6 Surface preparation, priming, stopping and filling ......................................................................... 44  
8.1.7 Coating systems for interior use ....................................................................................................... 46  
8.1.8 Coating systems for exterior use ...................................................................................................... 46  
8.1.9 Flame-retardant treatments ............................................................................................................... 48  
8.2 Wood-based panels products ........................................................................................................... 48  
8.2.1 Characteristics .................................................................................................................................... 49  
8.2.2 Preparation and coating systems ..................................................................................................... 50  
8.3 Iron and steel ....................................................................................................................................... 51  
8.3.1 General ................................................................................................................................................. 51  
8.3.2 Characteristics .................................................................................................................................... 52  
8.3.3 Design considerations ....................................................................................................................... 52  
8.3.4 Surface preparation and priming ...................................................................................................... 53  
8.4 Non-ferrous metals and metallic coatings ....................................................................................... 57  
8.4.1 Characteristics .................................................................................................................................... 57  
8.4.2 Surface preparation for non-ferrous metals .................................................................................... 58  
8.4.3 Priming ................................................................................................................................................. 60  
8.4.4 Coating systems for interior and exterior use ................................................................................. 62  
8.5 Plaster, external rendering, concrete (including lightweight and autoclaved aerated 
blocks), brick and stone – General considerations ........................................................................ 62  
8.5.1 Characteristics .................................................................................................................................... 62  
8.5.2 Coating systems for interior use ....................................................................................................... 64  
8.5.3 Coating systems for exterior use ...................................................................................................... 65  
8.6 Plaster .................................................................................................................................................. 67  
8.6.1 Characteristics .................................................................................................................................... 67  
8.6.2 Surface preparation and priming of plaster ..................................................................................... 68  
8.6.3 Coating systems for plaster .............................................................................................................. 68  DRS 554: 2023 
v                ©RSB2023- All rights reserved 
 8.7 External rendering ............................................................................................................................... 68  
8.7.1 Characteristics ..................................................................................................................................... 68  
8.7.2 Coating systems for external renderings ......................................................................................... 69  
8.8 Concrete ............................................................................................................................................... 70  
8.8.1 General ................................................................................................................................................. 70  
8.8.2 Coating systems for concrete ............................................................................................................ 70  
8.9 Brick and stone .................................................................................................................................... 71  
8.9.1 Characteristics ..................................................................................................................................... 71  
8.9.2 Coating systems for bricks and stone .............................................................................................. 72  
8.10 Precast concrete blocks ..................................................................................................................... 73  
8.10.1 Characteristics ..................................................................................................................................... 73  
8.10.2 Coating systems for precast concrete blocks ................................................................................. 74  
8.11 Cement-based sheets, boards and components ............................................................................. 74  
8.11.1 Coating systems for cement-based sheets, boards and components .......................................... 75  
8.12 Paper and wallcoverings including plasterboard ............................................................................ 76  
8.12.1 Characteristics ..................................................................................................................................... 76  
8.12.2 Removal of paper and wallcoverings ................................................................................................ 76  
8.12.3 Coating systems for paper, wallcoverings and plasterboard ......................................................... 77  
8.13 Plastics ................................................................................................................................................. 78  
8.13.1 General ................................................................................................................................................. 78  
8.13.2 PVC-U components ............................................................................................................................. 78  
8.13.3 GRP components ................................................................................................................................ 79  
8.13.4 Plastics coated metal .......................................................................................................................... 79  
8.13.5 Expanded polystyrene ........................................................................................................................ 80  
8.14 Glass and inorganic glazed surfaces ................................................................................................ 80  
8.14.1 General ................................................................................................................................................. 80  
8.14.2 Coating systems for glass and inorganic surfaces ......................................................................... 80  
8.15 Bituminous surfaces and materials ................................................................................................... 81  
8.15.1 General ................................................................................................................................................. 81  
8.15.2 Bituminous paints and coatings ........................................................................................................ 81  
8.15.3 Preservative treatments ...................................................................................................................... 82  
8.15.4 Asphalt and bitumen ........................................................................................................................... 82  
9 Application and practice ..................................................................................................................... 82  
9.1 Conditions of application ................................................................................................................... 82  
9.1.1 General ................................................................................................................................................. 82  
9.1.2 Temperature and humidity ................................................................................................................. 82  
9.1.3 Surface moisture ................................................................................................................................. 83  
9.1.4 Atmospheric pollution ........................................................................................................................ 84  
9.1.5 Air movement and wind ...................................................................................................................... 84  
9.1.6 Lighting ................................................................................................................................................ 84  
9.1.7 Seasonal factors .................................................................................................................................. 84  
9.2 Craft procedures and practices ......................................................................................................... 85  
9.2.1 Condition of surfaces.......................................................................................................................... 85  
9.2.2 Protection and cleanliness ................................................................................................................. 85  
9.2.3 Abrasion ............................................................................................................................................... 85  
9.2.4 Stopping and filling ............................................................................................................................. 86  
9.2.5 Preparation of materials ..................................................................................................................... 87  
9.2.6 Differing colours .................................................................................................................................. 88  
9.2.7 Intervals between application of successive coats ......................................................................... 88  
9.2.8 Inter-coat preparation ......................................................................................................................... 89  
9.2.9 Defective materials .............................................................................................................................. 89  
9.3 Application methods ........................................................................................................................... 89  
9.3.1 General ................................................................................................................................................. 89  
9.3.2 Brush application ................................................................................................................................ 89  
9.3.3 Roller application ................................................................................................................................ 91  
9.3.4 Paint pads ............................................................................................................................................ 92  DRS 554: 2023 
©RSB 2023- All rights reserved                  vi 
 9.3.5 Paint gloves ......................................................................................................................................... 93  
9.3.6 Spray application ................................................................................................................................ 93  
10 Inspection, sampling and testing ...................................................................................................... 96  
10.1 General ................................................................................................................................................. 96  
10.2 Inspection ............................................................................................................................................ 96  
10.2.1 General ................................................................................................................................................. 96  
10.2.2 Levels of inspection ........................................................................................................................... 97  
10.2.3 Duties of the inspector ....................................................................................................................... 97  
10.2.4 Final inspection ................................................................................................................................... 98  
10.3 Sampling and testing ......................................................................................................................... 99  
11 Maintenance ...................................................................................................................................... 100  
11.1 General ............................................................................................................................................... 100  
11.2 Factors affecting decisions on maintenance ................................................................................. 101  
11.2.1 Timing and frequency ...................................................................................................................... 101  
11.2.2 Condition of paintwork ..................................................................................................................... 101  
11.2.3 Variability of deterioration ............................................................................................................... 102  
11.2.4 Structural features ............................................................................................................................ 102  
11.2.5 Atmospheric pollution ...................................................................................................................... 102  
11.2.6 Building function .............................................................................................................................. 102  
11.2.7 Patch-painting ................................................................................................................................... 103  
11.3 Selection of coating systems for maintenance ............................................................................. 103  
11.3.1 General ............................................................................................................................................... 103  
11.3.2 Compatibility of coatings ................................................................................................................. 104  
11.3.3 Components of maintenance coating systems ............................................................................. 104  
11.4 Organization of maintenance work ................................................................................................. 105  
11.5 Preparation of painted surfaces ...................................................................................................... 105  
11.5.1 General ............................................................................................................................................... 105  
11.5.2 Removal of coatings ......................................................................................................................... 106  
11.5.3 Cleaning ............................................................................................................................................. 109  
11.5.4 Abrasion (rubbing down) ................................................................................................................. 109  
11.5.5 Priming ............................................................................................................................................... 110  
11.5.6 Stopping and filling .......................................................................................................................... 110  
11.5.7 Bringing forward ............................................................................................................................... 110  
11.5.8 Treatment of biological growth ....................................................................................................... 110  
11.5.9 Stains and discoloration .................................................................................................................. 112  
11.6 Application ........................................................................................................................................ 113  
Annex A (informative)  Types of coatings ................................................................................................... 114  
A.1 General ............................................................................................................................................... 114  
A.2 Conventional coatings ..................................................................................................................... 114  
A.3 Specialist coatings ........................................................................................................................... 114  
A.4 Factory-applied coatings ................................................................................................................. 115  
Annex B (normative)  Health and safety ...................................................................................................... 116  
B.1 Hazards .............................................................................................................................................. 116  
B.1.1 General ............................................................................................................................................... 116  
B.1.2 Lead paints ........................................................................................................................................ 117  
B.1.3 Fungicidal washes and coatings ..................................................................................................... 117  
B.1.4 Vapours, fumes and dusts ............................................................................................................... 117  
B.2 Injury to eyes and skin ..................................................................................................................... 118  
B.3 Fire an explosion .............................................................................................................................. 119  
B.4 Noise .................................................................................................................................................. 119  
B.5 Spillages ............................................................................................................................................ 120  
B.6 Waste disposal .................................................................................................................................. 120  DRS 554: 2023 
vii                ©RSB2023- All rights reserved 
 Annex C (informative)  Wood ........................................................................................................................ 121  
C.1 Design considerations ...................................................................................................................... 121  
C.2 Characteristics ................................................................................................................................... 122  
C.2.1 Structure ............................................................................................................................................. 122  
C.2.2 Heartwood and sapwood .................................................................................................................. 122  
C.2.3 Moisture content ................................................................................................................................ 122  
C.2.4 Permeability and penetration of liquids .......................................................................................... 122  
C.2.5 Extractives ......................................................................................................................................... 122  
C.2.6 External influences – Moisture ........................................................................................................ 123  
C.2.7 Preservative treatments .................................................................................................................... 123  
C.2.8 Knot treatment ................................................................................................................................... 123  
C.2.9 Coating systems for interior use ..................................................................................................... 124  
C.2.10 Coating systems for exterior use .................................................................................................... 124  
C.3 Wood-based panels products .......................................................................................................... 125  
C.3.1 Characteristics ................................................................................................................................... 125  
Annex D (informative)  Fire............................................................................................................................ 128  
D.1 General ............................................................................................................................................... 128  
D.2 Fire behaviour of coating and substrate ......................................................................................... 128  
D.3 Fire testing and classification of construction products with coating films .............................. 128  
Annex E (informative)  Anti-graffiti treatments ........................................................................................... 130  
E.1 General ............................................................................................................................................... 130  
E.2 Removal .............................................................................................................................................. 130  
E.3 Prevention and damage limitation – anti-graffiti coatings ............................................................ 131  
E.3.1 General ............................................................................................................................................... 131  
E.3.2 Sacrificial coatings ............................................................................................................................ 131  
E.3.3 Semi-permanent coatings ................................................................................................................ 131  
E.3.4 Permanent coatings .......................................................................................................................... 132  
E.3.5 Application of anti-graffiti coatings ................................................................................................. 132  
Annex F (informative)  Constituents of coatings ........................................................................................ 133  
F.1 General ............................................................................................................................................... 133  
F.2 Binders ............................................................................................................................................... 133  
F.2.1 General ............................................................................................................................................... 133  
F.2.2 Solvent-borne binders ...................................................................................................................... 133  
F.2.3 Water-borne binders ......................................................................................................................... 134  
F.2.4 Chemically-curing binders ............................................................................................................... 134  
F.2.5 Lacquers ............................................................................................................................................. 135  
F.2.6 Inorganic (cement and silicate) binders.......................................................................................... 135  
F.2.7 Bituminous binders ........................................................................................................................... 135  
F.3 Solvents and thinners ....................................................................................................................... 135  
F.3.1 General ............................................................................................................................................... 135  
F.3.2 Hydrocarbon solvents....................................................................................................................... 136  
F.3.3 Oxygenated solvents ........................................................................................................................ 136  
F.3.4 Water ................................................................................................................................................... 136  
F.4 Pigments ............................................................................................................................................ 136  
F.4.1 General ............................................................................................................................................... 136  
F.4.2 White pigments .................................................................................................................................. 136  
F.4.3 Tinting pigments ................................................................................................................................ 137  
F.4.4 Extenders ........................................................................................................................................... 137  
F.4.5 Corrosion-inhibitive pigments ......................................................................................................... 137  
F.4.6 Laminar pigments .............................................................................................................................. 137  
Annex G (informative)  Paint colours ........................................................................................................... 138  
Annex H (informative)  Iron and steel ........................................................................................................... 139  DRS 554: 2023 
©RSB 2023- All rights reserved                  viii 
 H.1 Characteristics .................................................................................................................................. 139  
H.2 Cast iron ............................................................................................................................................ 139  
H.3 Wrought iron ..................................................................................................................................... 139  
Annex I (informative)  Plaster ....................................................................................................................... 140  
I.1 General ............................................................................................................................................... 140  
I.2 Lightweight plasters ......................................................................................................................... 140  
Annex J (informative)  Paper and wallcoverings ........................................................................................ 141  
J.1 General ............................................................................................................................................... 141  
J.2 Plasterboard ...................................................................................................................................... 142  
Annex K (informative)  Bricks, stone and concrete blocks ....................................................................... 143  
K.1 Bricks and stone ............................................................................................................................... 143  
K.1.1 Clay bricks ......................................................................................................................................... 143  
K.1.2 Calcium silicate (sandlime or flintlime) bricks .............................................................................. 143  
K.1.3 Concrete bricks ................................................................................................................................. 143  
K.1.4 Stone .................................................................................................................................................. 143  
K.2 Concrete blocks ................................................................................................................................ 144  
K.3 Cement-based sheets, boards and components ........................................................................... 144  
K.3.1 General ............................................................................................................................................... 144  
K.3.2 Asbestos and fibre-cement goods .................................................................................................. 144  
K.3.3 Cement-based insulating boards, tiles and planks ....................................................................... 145  
K.3.4 Glass fibre reinforced concrete (GRC) components ..................................................................... 145  
Annex L (informative)  Conditions of application  (temperature and humidity)...................................... 146  
 DRS 554: 2023 
ix                ©RSB2023- All rights reserved 
 Foreword 
Rwanda Standardsarepreparedby Technical Committees and approved by Rwanda Standards Board (RSB) 
Board of Directors in accordance with the procedures of RSB, in compliance with Annex 3 of the WTO/TBT 
agreement on the preparation, adoption and application of standards. 
The main task of technical committees is to prepare national standards. Final Draft Rwanda Standards 
adopted by Technical committees are ratified by members of RSB Board of Directors for publication and 
gazettment as Rwanda Standards. 
DRS 554 was prepared by Technical Committee RSB/TC  056, Paints, Varnishes, Adhesives and Related 
Products.  
In the preparation of this standard, reference was made to the following standard: 
1) KS 2791: Painting of buildings — Code of practice 
The assistance derived from the above source is hereby acknowledged with thanks. 
Committee membership  
The following organizations were represented on the Technical Committee on Paints, Varnishes, Adhesives 
and Related Products (RSB/TC 056) in the preparation of this standard. 
Star Construction and Consultant (SCC) Ltd 
Rwanda Inspectorate, Competition and Consumer Protection Authority (RICA) 
Ministry of Environment (MoE) 
Rwanda Forensic Laboratory (RFL) 
Rwanda Investigation Bureau (RIB) 
University of Rwanda/College of Sciences and Technology (UR/CST) 
Kigali Water Ltd 
EARTHENABLE Ltd 
AMACO Paints 
Shalom Paints DRS 554: 2023 
©RSB 2023- All rights reserved                  x 
 Standards for Sustainability 
REX Paints 
AMEKI Color 
Rwanda Standards Board(RSB) – Secretariat DRS 554: 2023 
xi                ©RSB2023- All rights reserved 
 Introduction 
The most important functions of paints are protection and decoration of a substrate. The threefactors sunlight, 
moisture and heat affect the durability of paint coatings and the durability ofsubstrates (wood, plastics, etc.). 
Although, each factor can independently lead to deterioration,the effect of the combination of the three factors 
is much more severe than each factorseparately. Each of them can lead to the breakdown of the resin in 
painted surfaces whichbinds (holds) the pigment to the substrate surface. The more resin available 
tocompletely coata pigment particle, the more forcefully the particle is bound to a surface. 
It is the fact that premium paints have a high ratio of resin to pigment. A low-cost paint typically has a high 
pigment content relative to resin content as pigment is less expensive than resin. Although a high pigment 
content paint has an excellent “hiding” ability, high pigment content paints with low resin contents are unable 
to resist exposure to sunlight and moisture. Gloss paints have more resin than semi-gloss paints, and semi-
gloss paints have more resin than flat paints. Gloss paints have the most resistance to ultraviolet radiation and 
moisture; flat paints have least. 
Presently, there are so many companies manufacturing various types of paints under different brand names. 
The paints covered in this document are taken as reference to elaborate the various technical details in case 
of using them in structures other than bridge structures. In subsequent chapters, the general guidelines are 
prepared to facilitate the field personals to carry out the painting work on plastered, metallic and wooden 
surfaces along with the defects and their remedies, which are covered in detail. 
 
 DRS 554: 2022 
1                ©RSB2023- All rights reserved 
 Painting of buildings— Code of practice 
1 Scope 
This Draft Rwanda Standard gives recommendations for good practice in initial painting and maintenance 
painting of buildings internally and externally, e.g. dwellings, offices, light industrial buildings, schools, 
hospitals, hotels and public buildings generally, in which decoration is a significant and often the major factor. 
It takes into account the need to protect many building materials against the weather or other forms of attack 
normally encountered. 
The coatings referred to in this code are principally of conventional type, as defined in A.2, but limited 
reference is made to specialist coatings (A.3) and factory-applied coatings (A.4). 
In respect of materials generally, the document does not cover in detail the wide and constantly increasing 
range available. Some materials have been excluded because of their obsolescence, limited or specialized 
usage or, in the case of newly-developed products, lack of experience of their performance in service. 
This document does not also cover: 
a) decorative processes and other work usually carried out by specialists; 
b) the particular requirements of listed or historic buildings 
c) lime wash and distemper coatings; 
d) preservative treatments for structural timber; 
e) coatings for fire protection; and 
f) general safety hazards of access for painting (Annex C). 
The recommendations made in the code are intended to facilitate achievement of standards of finish likely to 
be acceptable in most cases in the types of buildings, providing that the work of other trades has been 
completed to a satisfactory standard. Where especially high standards of finish are necessary, more elaborate 
processes and systems than those described in the code might be necessary and should be specified 
accordingly. 
2 Normative references 
The following documents are referred to in the text in such a way that some or all of their content constitutes 
requirements of this document. For dated references, only the editioncited applies. For undated references, 
the latest edition of the referenced document (including any amendments) applies. 
RS ISO 4618   
©RSB 2023- All rights reserved                  2 
 ISO 12944 , General title of series of parts — Part c: Title of part  
ISO 16053, Paints and varnishes — Coating materials and coating systems for exterior wood — Natural 
weathering test  
EAS 1054, Black  bituminous paint for cold application —Specification  
ISO 16311-1, Maintenance and repair of concrete structures — Part 1: General principles  
ISO 16311-2, Maintenance and repair of concrete structures — Part 2: Assessment of existing concrete 
structures  
ISO 16311-3, Maintenance and repair of concrete structures — Part 3: Design of repairs and prevention  
ISO 16311-4, Maintenance and repair of concrete structures — Part 4: Execution of repairs and prevention  
ISO 7783:2018, Paints and varnishes — Determination of water-vapour transmission properties — Cup 
method 
ASTM E 1185-15,  
RS EAS 929:2019 Solvent-based paint remover — Specification 
ISO 21887:2007 Durability of wood and wood-based products — Use classes 
ISO 15206:2010 Timber poles — Basic requirements and test methods 
ISO 14713-1, Zinc coatings — Guidelines and recommendations for the protection against corrosion of iron 
and steel in structures — Part 1: General principles of design and corrosion resistance  
ISO 14713-2, Zinc coatings — Guidelines and recommendations for the protection against corrosion of iron 
and steel in structures — Part 2: Hot dip galvanizing  
ISO 14713-3, Zinc coatings — Guidelines and recommendations for the protection against corrosion of iron 
and steel in structures — Part 3: Sherardizing  
ISO 9329-1, Seamless steel tubes for pressure purposes — Technical delivery conditions — Part 1: Unalloyed 
steels with specified room temperature properties  
ISO 9329-2, Seamless steel tubes for pressure purposes — Technical delivery conditions — Part 2: Unalloyed 
and alloyed steels with specified elevated temperature properties  
ISO 9329-3, Seamless steel tubes for pressure purposes — Technical delivery conditions — Part 3: Unalloyed 
and alloyed steels with specified low temperature properties  
ISO 9329-4, Seamless steel tubes for pressure purposes — Technical delivery conditions — Part 4: Austenitic 
stainless steels  DRS 554: 2022 
3                ©RSB2023- All rights reserved 
 ISO 2063-1, Thermal spraying — Zinc, aluminium and their alloys — Part 1: Design considerations and quality 
requirements for corrosion protection systems  
ISO 2063-2, Thermal spraying — Zinc, aluminium and their alloys — Part 2: Execution of corrosion protection 
systems 
ISO 8501-3, Preparation of steel substrates before application of paints and related products — Visual 
assessment of surface cleanliness — Part 3: Preparation grades of welds, edges and other areas with surface 
imperfections  
RS EAS 1055,  
3 Terms and definitions 
For the purposes of this standard, the terms and definitions given in RS ISO 4618 and the following apply. 
3.1 
thixotropy 
property of changing reversibly from a gel or semi-liquid state when at rest to a more liquid consistency when 
shearing forces are applied at a constant rate over a period of time 
NOTE Shearing forces include for example brushing or stirring. 
3.2 
flow 
extent to which a coating is able to flow out to a film of uniform thickness free from brush marks and similar 
irregularities produced by the method of application 
3.3 
undercoat 
relatively highly pigmented matt or mid sheen materials, applied to primed or previously painted surfaces 
before the application of finishing coats 
3.4 
ancillary materials 
materials other than coatings used in the painting of buildings 
NOTE Ancillary materials include for example cleaning agents, sterilizing washes, knotting, stoppers and fillers, 
mastics, paint removers and waterproofing treatments.  
©RSB 2023- All rights reserved                  4 
 4 Design considerations 
4.1 General 
4.1.1 Many modern building materials do not require painting. If, however, building materials are chosen 
which require painting for aesthetic or protective reasons, then design factors should be considered by the 
architect at the earliest possible stage. Specifiers need to consider design aspects from the perspective of 
coating selection, maintenance and expected service life. Opportunities for design change after construction 
are very limited. For some new build components, e.g. window frames, initial painting is best carried out 
industrially prior to installation. 
4.1.2 Correct selection of coating systems and clear, precise specifying of methods and processes are 
essential. However, this alone does not ensure that the chosen systems perform satisfactorily, and it is equally 
important that consideration be given to the factors described in Table 1. Of particular importance in relation to 
performances is the influence of design and detailing, proper organization and supervision and, in some 
circumstances, an effective inspection procedure. Exposure conditions are the consequence of construction 
and climatic factors (e.g. Table 2). The guidance on typical life to maintenance will be system specific and 
apply to mild and moderate exposure conditions as described in Table 2. Service life will be shorter under 
more severe conditions. 
4.1.3 Hazards to health and safety that might be encountered in the painting of buildings and the 
precautions that need to be taken are described in Annex B. Reference is also made to applicable legislation 
(see also Annex B). These aspects should be considered in terms of a safe system of work. The health and 
safety of all persons involved in the building during the painting process, including client, occupier, painter, 
supervisory and inspection staff needs to be ensured.  
4.1.4 All parts of a building to which coatings are to be applied should be designed to avoid, as far as 
possible, the creation of features or conditions that can cause difficulties in application, impair the 
performance of coatings or promote decay or corrosion of structural materials. 
4.2 Accessibility 
4.2.1 Spaces between adjacent wood or metal members, e.g. in roof trusses, should be sufficiently wide to 
allow access for painting. Alternatively, hidden or contact surfaces should receive protective treatment before 
assembly or erection. Pipes and similar components should be fixed sufficiently clear of walls to allow them to 
be painted completely.  
4.2.2 Access for external repainting should be considered at the design stage. Where necessary, 
scaffolding should be provided. 
NOTE The need for scaffolding for initial or maintenance painting will add considerably to the costs. 
4.3 Control of moisture 
4.3.1 Penetration of moisture is a common cause of the premature failure of coatings; it could also lead to 
biological decay or corrosion of structural materials. Attention should be paid to the design and location of 
damp-proof courses and membranes, vapour barriers, flashings, weathering, drip- mouldings and throatings. 
Measures should be taken to prevent the retention of water on horizontal surfaces, e.g. by bevelling or sloping 
them or, in the case of structural metalwork, by providing drainage holes. Rainwater run-off or dripping on to 
coated surfaces should be prevented by appropriate detailing (see also C.2.6 and 8.3.3). DRS 554: 2022 
5                ©RSB2023- All rights reserved 
 NOTE Condensation is likely to occur in most buildings both externally and internally. External condensation (i.e. 
dew) will in combination with rainfall contribute to the overall time of wetness with detrimental effects on durability. 
Internally persistent condensation can cause failure of coatings both physically and through biological attack. The latter 
includes surface moulds and in the case of interstitial condensation an increased risk of decay. 
4.3.2 Measures to prevent or minimize condensation should be incorporated at the design stage but choice 
of coating can also make a contribution (see 4.6.4.2 and 4.6.4.3). 
4.4 Profiles 
Coatings have a tendency to recede from sharp edges during application and this could result in the film 
having inadequate thickness at these points. Timber arises should be slightly rounded, a radius of 1 mm to 2 
mm for timber other than sills and thresholds usually being sufficient: sills and thresholds might need a 3 mm 
rounding. Sharp edges of metal, e.g.: burrs and nibs, should be removed before painting. 
4.5 Selection of materials 
4.5.1 General 
Materials used in the painting of buildings can be divided into three main categories: 
a) pigmented coatings, e.g.: primers, undercoats, paints and wood stains; 
b) unpigmented coatings, e.g.: varnishes; 
c) ancillary materials, e.g.: fillers, stoppers and materials similarly used in the preparation of surfaces or in 
coating systems. 
Materials should be selected from Tables 3 to Table 11 in accordance with 7.1 to 7.3 for coatings and in 
accordance with 7.4 for ancillary materials. 
4.5.2 Volatile organic compounds 
When selecting coatings, the volatile organic compound (VOC) content of coatings and its effect on the 
environment should be taken into account. 
4.6 Selection of coating systems 
4.6.1 General 
4.6.1.1 A number of factors should be considered when selecting coating systems. Selection is often be 
made on a qualitative basis, judging the relative importance of the factors in relation to particular 
circumstances. If more than one type of system meets the specification, then selection might be made on the 
basis of relative cost, availability or individual preference. 
NOTE Care should be taken to ensure that factors are comparable; lower initial costs might well be more than 
outweighed by shorter life and consequent higher maintenance expenditure. In other circumstances, a single factor might 
exert so strong an influence that selection is limited to a single type of system .  
©RSB 2023- All rights reserved                  6 
 4.6.1.2 Factors, which should be considered when selecting coating systems, are listed in Table 1. There is 
a considerable degree of interaction between factors involved, and they should not be considered in isolation. 
The selection of coating systems and their suitability for substrates or groups of substrates should be 
determined using Tables 12 to 18. 
NOTE Information is given in the relevant tables on the expected life to first maintenance in mild or moderate 
exposure conditions, which have been categorized in Table 2. 
4.6.1.3 Possible paintwork defects that might be encountered and the recommended remedial treatment for 
these should be determined using Table 19 and Table 20. 
4.6.2 Exposure conditions 
4.6.2.1 General and local exposure conditions and the conditions of service are major factors in the selection 
of coating systems. Reference should be made to 4.6.4 for information on special conditions that could 
influence selection. 
NOTE A broad distinction can be made between external and internal exposure conditions but, in either, there can be 
considerable variation in the severity of attack or rigours of service, even within a single building. Externally, the main 
variables are location, proximity to the coast and level and nature of atmospheric pollution but elevation, aspect and the 
direction of prevailing winds can also have a significant effect. Internally, high humidity and the presence of process 
chemicals and dust can create severe conditions. 
4.6.2.2 Table 2 indicates the broad categories of external and internal exposure conditions that might be 
encountered and illustrates factors that should be considered. It is intended to provide general guidance; it is 
not possible to take into account the many local variables that can influence the nature of the exposure 
conditions and the selection of coating systems in specific circumstances. 
4.6.3 Substrates and coating systems 
4.6.3.1 The properties of substrates and their influence on the selection of coating systems should be 
considered at the design stage (see Clause 8). 
NOTE For new build there are dominant economic and operational factors for the choice of substrates and methods 
of construction. Coatings may be required for aesthetic and/or protective reasons but cannot be expected to upgrade the 
performance of incorrectly specified building materials. The nature of the substrate will have a major impact on the 
suitability of specific coating systems. 
4.6.3.2 Building materials to which coatings are to be applied should be chosen for their inherent properties 
of durability and resistance to decay or corrosion in the exposure conditions in which they are to be used. 
Over-reliance should not be placed on the ability of coatings to upgrade the performance of inherently 
unsuitable materials, especially in circumstances where frequent maintenance is likely to be impracticable or 
uneconomic. 
4.6.3.3 Alternative or supplementary treatments, e.g.: galvanizing or sprayed metallic coatings (see 8.4.1.2), 
are available, as are ancillary treatments such as wood preservatives (see 8.1.5), to enhance the protection 
afforded by coatings. 
NOTE Where possible it is advantageous to undertake initial painting under controlled conditions, e.g.: factory. This 
is often more satisfactory than site application and can offer a wider choice of systems. DRS 554: 2022 
7                ©RSB2023- All rights reserved 
 4.6.4 Special conditions and requirements 
4.6.4.1 General 
Because of the diversity of conditions, substrates and coatings, especially in relation to chemical resistance, it 
is possible to provide only a general indication of the types of coatings that might be suitable. For detailed 
recommendations in specific circumstances, specialist advice should be sought. 
4.6.4.2 High humidity 
4.6.4.2.1 Most paints are resistant to the levels of humidity normally encountered internally in most domestic 
and non-industrial situations. Where conditions of moderate or high humidity prevail intermittently, as in 
kitchens and bathrooms, only resistant coatings should be used. 
NOTE This will include most solvent-borne paints and some water-borne paints (7/1, 7/2, 7/3 and 7/4) 
4.6.4.2.2 The processes or activities carried out in some buildings can give rise to conditions of constant or 
frequent high humidity or cause surfaces to be splashed with water. (Examples where such conditions might 
prevail include swimming baths, laundries and factories engaged in the manufacture of food and drink, paper 
and synthetic and natural fibres.) In these conditions, and especially for the protection of steel, wood and other 
substrates vulnerable to attack by moisture, specifically moisture- resistant coatings should be used. 
4.6.4.2.3 Acrylated rubber paints (11/5), especially high-build types, have good moisture resistance and are 
available in a wide range of colours. Where colour is not important, bituminous coatings (see Table 10), 
including coal tar epoxies, can be used. Bituminous coatings can be used to provide semi-drying protective 
coatings with good moisture resistance which are suitable for use on surfaces not subject to handling or 
abrasion. 
4.6.4.2.4 Moisture-resistant protective coatings should be applied in accordance with the manufacturer's 
recommendations in regard to thickness, preparation and priming. 
NOTE Many moisture-resistant protective coatings need to be applied at a thickness of 100 mm or more. 
4.6.4.3 Condensation 
4.6.4.3.1 Condensation should be prevented or controlled by providing good ventilation to remove moisture- 
laden air from buildings, preferably from a point near the source of moisture. Adequate levels of heating 
increase the capacity of the air to hold moisture but should be combined with good ventilation, otherwise the 
problem is aggravated. Thermal insulation also helps to reduce condensation by keeping surfaces warmer 
and reducing the cost of heating. 
NOTE Most condensation in buildings is caused by warm, moist air coming in contact with cooler surfaces. In 
domestic and non-industrial buildings, condensation is usually light and intermittent although, in some situations, it can be 
sufficient to cause water runs and drips, disfigure paintwork or promote mould growth. In dwellings, condensation is most 
likely to occur in kitchens and bathrooms, but water vapour can be carried by air currents through the house from these 
rooms and condense on cold surfaces in unheated areas. 
4.6.4.3.2 Paint treatment alone should not be used as an alternative to heating, ventilation and thermal 
insulation measures but, where condensation is moderate and occurs only intermittently, anti- condensation 
paints can be used. They usually contain aggregates with insulating or absorptive properties. Some coatings  
©RSB 2023- All rights reserved                  8 
 have a textured surface that helps to reduce water runs and drips, but these tend to hold dirt and are not 
easily cleaned. Absorptive types should be used only in situations where it is to be expected that 
condensation will be followed by conditions favourable to drying out of absorbed moisture. 
4.6.4.3.3 Where the function of a building gives rise to conditions of constant or frequent high humidity and the 
measures to prevent or reduce condensation in the preceding paragraphs are impracticable or not fully 
effective, priority should be given to the protection of substrates vulnerable to moisture attack by using 
specifically moisture-resistant coatings, as described in 4.6.4.2. 
4.6.4.4 Mould growth 
NOTE Typically, mould has a black, sooty appearance and might be mistaken for dirt although some moulds are 
coloured. It is often possible to distinguish mould from dirt and chemical stains by examination with a magnifying glass 
(X10 or higher) when the filaments or hyphae characteristic of most moulds might be seen. 
4.6.4.4.1 Moulds germinate and grow when the relative humidity at a surface rise above 80% and where there 
is a supply of nutrients. Mould growth should be avoided by: 
a) Ensuring the relative humidity does not exceed 70%. Because of its dependence upon a supply of 
moisture, the growth of mould is most effectively inhibited by reducing humidity and preventing 
condensation by good ventilation, adequate heating and thermal insulation, as indicated in 4.6.4.3; or 
b) applying moisture-resistant protective coating (see 4.6.4.2) and sterilizing the surface by application of 
a fungicidal wash at regular intervals. Proprietary washes containing fungicides are available, and 
some leave an inhibitive residue on the surface; a solution of household bleach also kills mould but 
does not have any residual inhibitive properties; or 
c) applying mould-resistant paints in domestic and non-industrial situations. When mould-resistant paints 
or washes are to be used where foodstuffs are prepared or stored, it should be ensured that there is 
no risk of food products being contaminated with toxic substances or their flavours affected. Mould-
infected, previously decorated internal surfaces before painting, should be treated in accordance with 
11.5.8. 
NOTE Mould-resistant paints usually contain mould-inhibitive additives. 
4.6.4.4.2 Some more toxic mould-inhibitive additives might not be suitable for use in situations where 
foodstuffs are processed. 
4.6.4.5 Chemical attack 
4.6.4.5.1 Coatings are likely to be attacked chemically by high concentrations of acids and alkalis, acidic and 
alkaline substances, alcohols, oils, fats and greases, solvents and fresh and salt water. 
4.6.4.5.2 In mildly acidic industrial exposure conditions, alkyd gloss and drying-oil/resin micaceous iron oxide 
paints can be used and should be applied to prepared and primed surfaces in systems of adequate thickness 
to achieve a defect-free film. Where there is a need for resistance to heavy fume attack or direct contact with 
chemicals, chemical-resistant coatings should be used. 
NOTE Chemical-resistant coatings include acrylated rubber, two-pack epoxy and polyurethane, coal-tar epoxy and 
bituminous types (see Table 10 and Table 11). DRS 554: 2022 
9                ©RSB2023- All rights reserved 
 4.6.4.5.3 The resistance of any of the coatings described in Table 11 is dependent on the specific agent and 
the form and severity of attack. When there appears to be a need for a chemical-resistant coating, specialist 
advice should be sought unless there is previous experience of the satisfactory performance of a particular 
type of coating in similar circumstances. 
4.6.4.6 Fire 
For further information on fire, see Annex D. 
4.6.4.6.1 Painted surfaces 
A painted surface should be considered as a thin film of flammable material in close contact with a substrate. 
The potential for the release of flammable volatiles (and therefore for a fire to occur) is a function of the nature 
of the paint film itself and the nature of the substrate. Paints would not normally affect the flame-spread rating 
of the unpainted surfaces (see 4.6.4.6.2.) 
4.6.4.6.2 Resistance to surface spread of flame 
NOTE Attention is drawn to the Building Regulations which require that, in certain types of buildings, the materials of 
which walls and ceilings are constructed conform to specified minimum requirements in relation to the spread of flame 
across the surfaces. 
4.6.4.6.2.1 Paints should either be of conventional type conforming to specified minimum requirements in 
relation to the spread of flame across the surfaces. Flame-retardant paints can be conventional paints 
containing flame- retardant additives or types that intumesce (swell on heating). They should be applied as 
recommended by the manufacturer. The flame spread rating of paint cannot be expressed in isolation but only 
in relation to its performance on a specified substrate. Reference should be made to the manufacturer's 
details of the ratings of their paints when applied to specified substrates. 
4.6.4.6.2.2 The flame spread rating of a painted surface can worsen with increasing film thickness or in 
situations where conventional paints are applied over flame-retardant types. In the latter event, compatibility 
problems can also arise. To avoid such difficulties, details of systems applied, including dates of application 
and types or brands of paints used, should be recorded for future reference. It can also be helpful to label 
surfaces to which flame-retardant paints have been applied. 
NOTE Where Building Regulations require the materials of which walls or ceilings are constructed to have a specified 
flame- spread rating, flame-retardant paints applied on site cannot be used to upgrade materials that do not meet Building 
Regulation requirements. 
4.6.4.7 Resistance to abrasion 
NOTE Coatings resistant to abrasion might be required for floors, machine surfaces, storage racks and bins, 
handrails and similar items, especially in factories and commercial buildings. There might also be a need for watt and 
ceiling finishes to be resistant to frequent vigorous cleaning in such places as dairies, abattoirs and food preparation 
areas. 
Pigmented and clear two-pack epoxy and polyurethane coatings should be used where resistance to abrasion 
is a major consideration, but their use might be limited by the nature of the substrate or the conditions of 
application.  
©RSB 2023- All rights reserved                  10 
 NOTE The modified one-pack types, although lower in abrasion resistance, can also be used, as they are subject to 
fewer restrictions in use and perform reasonably well in many situations; one-pack epoxy ester types, for example, can be 
used as floor and deck paints, often with a non-slip additive. Some modified alkyd paints are reasonably resistant to 
abrasion and can be used for painting machinery and similar applications. Multi-colour finishes (7/14) can be used for 
walls in many interior hard wear situations. 
4.6.4.8 Anti-graffiti treatments 
4.6.4.8.1 Paint graffiti is an increasing problem in buildings and any organization with buildings that are 
vulnerable to attack should have a policy on removal or protection. New or undamaged surfaces should be 
assessed for the likely risk and cost of countermeasures. Choices for the prevention include sacrificial, semi-
permanent and permanent coatings (see E.3.1). 
4.6.4.8.2 Where graffiti is already a problem, measures of removal or obliteration should be assessed taking 
into account any hazards to the public during removal operations. Physical and chemical methods are 
available but the choice of method will depend on the nature of the marker and the substrate. Specialist 
manufacturers should be consulted and preliminary testing carried out on small areas (see E.1 and E.2). 
NOTE For further information on anti-graffiti treatments, see annex E. 
Table 1 — Selection of coating systems 
Issue Question  Action 
Exposure 
conditions What is the general atmospheric exposure conditions, 
external and internal?  Consider location and functions of buildings  
What localized or intermittent conditions (e.g.: fumes, 
condensation, heat, vulnerability to abrasion or wear) 
exist or are to be expected?  Refer to 7.1, Table 2 and 4.6.4. Consider  
possible future developments or changes in  
usage, which might alter the local exposure  
conditions  
Function  What are the functional requirements (e.g.: of 
protection, decoration, hygiene or special function)?  Refer to 7.1 and 4.6.4. Design remit and 
experience. Consider substrate. Consider  
exposure conditions (see 4.6.2)  
Are there any relevant statutory requirements (e.g.: 
under the Building Regulations or Factories Act) 
affecting selection?  Relevant legislation (see also Annex B)  
Substrate What substrates are involved?  Design, remit, specification or inspection  
Do their characteristics influence the selection of 
coating systems?  Refer to 8.1 to 8. 15 
Special 
constraints 
on selection Are there constraints relating to the composition of the 
coatings in some situations (e.g.: in food factories 
because of the risk of toxicity or tainting)?  Consult client, industry association or 
supplier  
Are the materials chosen to minimize solvent content 
and the systems of working specified compliant with 
legislation?  Refer to Clause 10 and Annex B  
Are any constraints imposed by the conditions under 
which the work has to be carried out (e.g.: requiring the 
use of coatings which dry very quickly)?  Consult client, contractor or supplier. Refer to  
9.1  
Are there constraints imposed on colour choice by 
reason of solar gam?  Refer to 8.1.4.2  
Does the condition of the substrate (e.g.: its high 
moisture content) impose constraints on the selection?  Ascertain condition, expected or actual, at 
time of treatment. Refer to 8.1 to 8.15  
Coatings  Which coating systems are available?  Consider answers to preceding questions.  
Refer to Tables 3 to 11 and 8.1 to 8.15.  
Consult suppliers  
Are the coatings readily available from the usual 
sources or is special order or manufacture required?  Consult suppliers  
Are the coatings suitable for site or factory application?  Consult suppliers  
Are there any restrictions on methods of application on Consult suppliers. Refer to Clause 9 for  DRS 554: 2022 
11                ©RSB2023- All rights reserved 
 site?  information on application methods  
Is application by specialist contractors required?  Consult supplier. Refer to Tables 3 to 11  
Has the environmental impact of the chosen system 
been considered?  Consult supplier. Refer to Tables 3 to 11  
Cost and 
Maintenance  What is the likely first cost of the system, including 
preparation, materials and application?  Cost analysis of previous work of a similar 
nature. Consult contractors and suppliers  
What is the expected life of the system to first 
maintenance?  Experience of similar systems. Refer to 
Tables 12 to 17  
Does the system provide a satisfactory base for 
maintenance type perhaps with coatings of different 
type?  See 11.3  
Table 2 — Exposure condition categories 
Severity of 
exposure Corrosivity 
category (see 
ISO 12944-2) Exterior  Other exterior 
factors Interior Other interior 
factors 
Mild C1 (very low) - - Heated 
buildings  
with clean  
atmospheres, 
e.g.offices, 
shops, schools, 
hotels and  
domestic 
situations  Light soiling,  
abrasion or  
handling of 
surfaces  
 
C2 (low) Inland areas 
(more  
than 10 km 
from the  
coast), 
nonindustrial  
with low  
levels of 
pollution  
and average 
rainfall  - Unheated 
buildings  
where 
condensation  
might occur, 
e.g.  
depots, sports 
halls  - 
Moderate C3 (medium) Urban and 
industrial  
atmospheres,  
moderate sulfur 
dioxide 
pollution.  
Coastal areas 
with low salinity  - More frequent  
moderate  
condensation, 
e.g. in kitchens, 
bathrooms, 
washrooms etc.  
Production 
rooms  
with high 
humidity  
and some air  
pollution, e.g. 
food processing  
plants, 
laundries,  
breweries, 
dairies  Moderate  
soiling, abrasion  
and handling of  
surfaces  
Severe C4 (high) Industrial areas 
and coastal 
areas with 
moderate Areas with a 
driving rain 
index of 7 or 
more Exposure 
conditions  
subject to 
frequent  Exposure  
conditions in  
which heavy  
soiling or   
©RSB 2023- All rights reserved                  12 
 salinity.Coastal 
ship- and  
boatyards  high humidity or  
heavy  
condensation,  
especially if  
pollutants, e.g.  
sulfur dioxide or  
ammonia, are 
present. 
Chemicalplants, 
swimming  
pools  hygiene  
requirements  
necessitate  
frequent  
cleaning of 
surfaces.  
Surfaces 
subject  
to heavy  
abrasion or  
impact  
 
Very severe C5-I (very high, 
industrial) 
C5-M (very 
high, marine) Industrial areas 
with high humidity 
and aggressive 
atmosphere  
Coastal and 
offshore areas 
with high salinity  - Buildings or areas  
with almost  
permanent  
condensation and  
with high pollution  Surfaces in  
contact with  
chemicals,  
chemical  
solutions,  
process liquors  
and other  
aggressive  
agents  
NOTE       For wood, the exposure conditions are better classified in accordance with ISO 16053, which takes into account 
the construction and the climate.  
Table 2 — Primers for wood 
Ref. Description  General composition  Characteristics and usage  
3/1 Opaque primer Pigmented primer, solvent-borne  
(typically alkyd) or water-borne  
(typically vinyl acetate or acrylic), for 
general use under paints  Primers of this type are suitable for general 
use on wood, fibre boards and chipboards  
 
3/2 Opaque primers  
conforming to BS 7956,  
Type AA) Solvent-borne (typically alkyd) or  
water-borne (typically acrylic)  
pigmented primers of 3/1, but  
formulated for improved exterior  
durability  General purpose 
 
3/3 Semi-transparent  
primers conforming to  
BS 7956, Type BA)  Solvent- or water-borne as 3/2 using 
transparent pigments  Semi-transparent dual-purpose primers 
designed for over coating with either stain 
finishes or paints.  
Often used as the factory-applied primer for 
joinery. They are generally of lower durability 
than 3/2  
primers and should be over coated with 
minimum delay  
3/4 Opaque primers  
conforming to BS 7956,  
Type CA)  Solvent-borne or water-borne primers 
as 3/2 with stain blocking properties  Primers that can be used directly over knots, 
resinous timbers and timbers pretreated with  
preservatives, such as metallic 
naphthenates, known to discolour 
subsequently applied paint films 
3/5 Ready-mixed aluminium 
primers conforming to 
BS 4756  Solvent-borne drying-oil/resin type 
binder with aluminium pigment  
 An alternative to conventional solvent-borne 
wood primer more suitable for woods that are 
resinous or have been treated with copper 
naphthenate wood preservative or creosote. 
Relatively impermeable to moisture. 
Application of an additional coat of 
undercoat/finish might be required to 
obliterate grey primer colour  
3/6 Preservative primers  Unpigmented or lightly pigmented 
solution of resins and fungicides in First coat of some proprietary wood coating 
systems, intended to seal porous and DRS 554: 2022 
13                ©RSB2023- All rights reserved 
 water or organic solvent  weather exposed surfaces and inhibit fungal 
colonization. Beneficial for treating 
weathered wood surfaces after mechanical 
preparation  
 
Table 4 — Primers for metal 
Ref. Description  General composition  Characteristics and usage  
4/1 Pre-treatment, 
wash or etching 
primer, two-pack Typically, polyvinyl butyral resin 
solution with phosphoric acid (as 
separate component) and a 
pigment (chromate containing 
primers now largely superseded by 
chromate-free primers)  The main function of these primers is to 
improve adhesion of paint systems to 
non-ferrous metals.  
They can also be used to provide 
temporary  
protection to blast-cleaned steel and 
sprayed metallic coatings. The two-pack 
types generally give superior 
performance but might be less 
convenient to use. Application of primers 
of this type does not usually obviate the 
need for the application of a normal type 
of primer subsequently. Most pre-
treatment  
primers can be used in conjunction with  
conventional and specialist coating 
systems  4/2 Pre-treatment, 
wash or etching 
primer, one pack.  Typically, polyvinyl butyral/phenolic 
resin solution with tinting pigment  
4/3 Mordant solution  Water-borne pre-treatment for 
galvanized and non-ferrous metals  Contains an indicator which darkens the 
surface of galvanized steel indicating that 
it has reacted  
4/4 Adhesion promoter  Water-borne pre-treatment for non-
ferrous metals and stainless steel  Pretreatment with low VOC content 
designed to improve adhesion of 
subsequent coating system to non-
ferrous metals and stainless steel  
4/5 Zinc phosphate 
primer (see also 
4/8 and 5/4)  Solvent-borne. Typically, drying oil/ 
resin type binder with zinc 
phosphate as the main inhibitive 
pigment. Other tinting pigments can 
be incorporated  Zinc phosphate offers advantages over 
other inhibitive pigments in being less 
toxic and neutral in colour. Zinc 
phosphate primers are fairly quick drying 
and can afford protection without 
finishing coats for reasonable periods. 
Established usage is for priming 
steelwork, but some types might be 
suitable for non-ferrous metals; refer to 
manufacturer’s recommendations  
4/6 Chromate primer  
(limited availability) 
for specialist use  Solvent-borne. Typically, drying oil/ 
resin type binder with zinc chromate 
as the main inhibitive pigment. Red 
oxide or other pigments can be 
incorporated  Vary according to formulation, but 
chromate primers are usually fairly quick-
drying and suitable for use on ferrous 
and non-ferrous metals  
4/7 Zinc-rich Primer A)  
conforming to BS  
4652 (two-pack),  
solvent-borne  Solvent-borne. Based on epoxy 
resin and supplied in two-pack form 
(zinc paste and curing agent)  A quick-drying metallic-grey primer for 
iron and steel with rust-inhibiting 
properties. Apply to well-prepared (e.g. 
blast-cleaned) steel only. Often used for 
touching up damaged zinc coatings, e.g. 
zinc sprayed or galvanized surfaces or 
as a prefabrication primer. Spray 
application is recommended, except on 
small areas   
©RSB 2023- All rights reserved                  14 
 4/8 Zinc-rich primer 
(one-pack)  Solvent-borne. Based on a non-
saponifiable medium, e.g. 
chlorinated rubber  A quick-drying metallic-grey primer for 
iron and steel with rust-inhibiting 
properties. Often used for touching up 
damaged zinc coatings, e.g. zinc sprayed 
or galvanized surfaces  
4/9 Zinc phosphate 
primer, waterborne Water-borne. Based on an acrylic resin 
dispersion in water and typically 
containing a zinc phosphate 
anticorrosive pigment  A quick-drying primer for iron and steel as 
well as non-ferrous metals including 
galvanizing. Some versions described as 
universal primer (5/4) and can be used on 
timber surfaces  
4/10 Two pack epoxy 
primer  Solvent-borne. Based on epoxy resin 
and usually polyamide and supplied in 
two-pack form  Surface tolerant primer, usually containing a 
leafing aluminium pigment, is suitable for 
application not only to manually prepared 
steel surfaces, but also over existing, sound 
paintwork  
NOTE – Advice should be sought when drying-oil/resin type paints are to be used over zinc-rich primers. 
Table 5 – Miscellaneous primers 
Ref. Description  General composition  Characteristics and usage  
5/1 Alkali-resisting 
primer Traditionally solvent-borne.  
Typically, alkali-resistant drying oil  
(e.g. tung)/resin type binder, lightly 
pigmented  Although described as alkali-resisting, 
primers of this type are intended for use 
on substantially dry, possibly alkali-
containing, surfaces mainly beneath 
drying-oil resin finishes; they will not  
necessarily prevent attack by alkalis on  
subsequent coats if the structure is very 
damp  
5/2 Primer or  
primer  
undercoat  Water-borne (typically based on an 
acrylic polymer). Might be identical 
in composition to 4/9 or 6/2  These primers are for use on dry plaster 
and similar surfaces. They might also be 
suitable for priming wood and building 
boards, metals (universal primer) and as 
undercoats (see 4/9 or 6/2)  
5/3 Primer-sealer  
Other descriptions  
include stabilizing  
primer or solution,  
penetrating primer 
or  
masonry sealer  Traditionally solvent-borne and 
lightly pigmented, or semi-
transparent with a marker pigment, 
to assist even application. May also 
be based on fine particle-sized 
water-borne  
acrylic  The essential function of a primer-sealer 
is to bind down powdery or friable 
residues of previous coatings which 
cannot be removed completely.  
Too much reliance should not be placed 
on the ability of this type of material to 
penetrate unsound coatings of substantial 
thickness, and as much as possible of the 
old material should be removed.  
Primer-sealers can also be used to 
reduce absorption on surfaces of high or 
uneven porosity.  
Masonry sealers are usually formulated 
specifically for use on exterior surfaces 
and might not be suitable for interior 
work: with other types, the reverse might 
apply. Reference should be made to the 
manufacturer’s recommendations  
5/4 Universal primer 
(see also 5/2) All-
purpose primer  Typically, drying-oil/resin type  
binder or water-borne acrylic with  
white or light-coloured pigments,  
usually including rust-inhibitive  
types, e.g. zinc phosphate  A universal primer is typically white or 
light grey and is convenient for small-
scale maintenance work involving patch-
priming of a variety of substrates, e.g. 
wood, metal and dry plaster. For new and DRS 554: 2022 
15                ©RSB2023- All rights reserved 
 large-scale work, primers  
formulated for specific substrates are 
generally to be preferred  
Table 6 – Undercoats  
Ref. Description  General composition  Characteristics and usag e 
6/1 Solvent-borne 
Traditionally drying-
oil/resin type This 
type of undercoat 
provides a matt or 
low sheen  
undercoat    
6/2 Water-borne 
undercoat or primer 
undercoat  Based on acrylic or other polymers 
pigmented as in 6/1. Might be 
identical in composition to 5/2.  These undercoats are quicker drying than 6/1 
and, in normal conditions permit same-day 
recoating. General usage as 6/1. As primers they 
might be suitable for priming dry plaster, building 
boards and wood. Only types conforming to BS 
7956 should be used for priming exterior 
woodwork.  
Table 7 – General pigment finishes 
Ref. Description  General composition  Characteristics and usage  
7/1 Solvent-borne gloss 
or midsheen finish 
Other descriptions  
include hard-gloss  
enamel and high 
gloss for gloss  
finishes; and 
eggshell, satin, silk 
and semi-gloss for 
midsheen finishes  Based on drying-oil/alkyd resin binder 
which might contain small amounts of 
polyurethane or other resins to 
increase hardness, flexibility or 
durability. Pigmented with titanium 
dioxide and/or lightfast, colored 
pigments  
 These are protective and decorative finishes 
suitable for interior and exterior use on most 
building surfaces. They have good durability and 
wearing properties in most conditions except 
those of direct chemical attack or very high 
humidity.  
Advice should be sought from the manufacture 
regarding the suitability of mid-sheen finishes for 
exterior use on different substrates. For solvent 
borne gloss or mid-sheen finish, drying and 
recoating times are variable according to 
composition but, usually, overnight drying 
between coats is required for drying-oil/alkyd 
resin types  
For water-borne gloss or mid-sheen finish under 
normal conditions, drying and recoating times are 
considerably shorter than solvent-borne and 
same day recoating is a possibility (see 
manufacturer’s  
instructions)  7/2 Water-borne gloss 
or mid-sheen finish 
Descriptive terms for 
sheen can be 
described as for 7/1  Typically based on acrylic 
dispersions. Might contain other 
modifying resins.  
Pigmented with titanium dioxide 
and/or light-fast, coloured pigments  
7/3 Solvent-borne matt 
or flat finish  Generally as for 7/1 adjusted to 
provide a matt finish  Essentially, this is a decorative finish for interior 
use only. Drying and recoating characteristics are 
usually similar to those of 7/1. Special purpose  
types, both water- and solvent-borne designed 
for renovating surfaces which might be weak, 
liable to cause staining of subsequent coatings, 
or subject to further drying (see also 7/5)  
7/4 Water-borne matt or 
flat finish Other  
Descriptions include 
emulsion paint, 
latex, vinyl or acrylic 
paint (see F.2.3)  Composition of binder typically based 
on vinyl or acrylic polymers or 
combinations of these, with titanium 
dioxide and/or coloured pigments  Water-borne are often less resistant than their 
solvent-borne counterparts, but the wear-
resistance and washability of some might 
approach those of the 7/1 mid-sheen finishes. 
They have advantages over the latter in ease of 
application to large areas, speed of drying 
(same-day recoating is usually possible), 
absence of solvent odour and ease of clean-up. 
They are widely used for ceilings and walls, 
mainly internally although some might be suitable  
©RSB 2023- All rights reserved                  16 
 for use on exterior walls. Choice of sheen level 
depends largely on location and aesthetic 
considerations but, in general terms, washability 
and resistance to soiling increase proportionately 
to the degree of sheen. Water-borne paints are 
generally more permeable to moisture than 
drying oil/resin finishes and only some are 
suitable for use in situations where humidity is 
high for long periods, e.g. in kitchens and 
bathrooms (see manufacturer’s 
recommendations)  
 
7/5 Contract and 
general purpose 
paint  Water-borne. Composition, typically, 
is similar to that of 7/4 but with higher 
pigment content and giving a matt  
finish  Higher pigment gives increased opacity, 
compared with 7/4 type, but at the expense of a 
reduction in washability and resistance to soiling. 
Paints of this type are frequently used for new 
interior walls and ceilings where, apart from 
economy in use, their high permeability allows 
drying-out of contained moisture  
7/6 Aluminium paint,  
general purpose  Traditionally, solvent-borne.  
Typically, drying-oil/alkyd resin binder 
pigmented with flake aluminium  The laminar nature of the pigment (see F.4.6)  
imparts moisture-resistance to aluminium paints,  
and their reflective and heat-resistant properties 
are useful in many situations. They are suitable 
for use on most building surfaces, but their 
widest application is on structural steelwork, 
storage vessels and heated metal surfaces  
7/7 Micaceous iron 
oxide paint, general  
purpose  
 Solvent-borne. Typically, drying-oil or 
drying-oil/resin type binder pigmented 
with micaceous iron oxide. Small 
amounts of other pigments can be 
incorporated to modify the natural 
colour (dark grey) of the main 
pigment  Because of the laminar nature of the pigment 
(see F.4.6) and the substantial thickness of the 
film, micaceous iron oxide paints provide good 
protection and are widely used extensively on 
structural steel, bridges, harbour installations and 
electricity transmission towers. On  
weathering, the coating develops a metallic 
sparkle. The dark colour of the pigment restricts 
the range of colours available, but over coating 
with alkyd gloss finish is often possible  
7/8 Masonry paint,  
water-borne,  
smooth or fine 
textured  Water-borne binder, typically based 
on acrylic, vinyl and other polymers 
formulated to have the degree of 
flexibility required for exterior use and 
pigmented with titanium dioxide 
and/or lime resistant coloured 
pigments.  
Some types are smooth; others 
contain fibre, sand or other agent to 
give a fine texture. Most contain an 
additive to inhibit mould and algal 
growth  These are essentially decorative coatings but 
have the weather-resistance and durability 
required in coatings for exterior walls. Both the 
smooth and the fine-textured paints can provide 
protection of concrete, etc. in combination with 
sealers, if needed, in accordance with 
manufacturer’s recommendations.  
These types of paint are not generally suitable for 
application to wood and metal. Formulations 
containing fibre, sand, etc. usually provide thicker 
films than the smooth types. The manufacturer 
should be consulted regarding the use on interior 
surfaces of masonry paints containing additives 
to inhibit mould and algal growth because of the 
possible toxic hazard  
7/9 Masonry paint, 
water-borne heavy-
textured  Compositions can vary considerably 
but consist generally of a heavy-
bodied water-borne binder, reinforced 
with coarse extenders and in some 
cases, fibrous material and 
aggregates.  
Pigmentation is similar to that of 7/8 
and mould/algal inhibitors might be 
incorporated  Coatings of this type provide thick (1 mm to 2 
mm), weather-resistant coatings, and experience 
indicates that they are capable of durability in 
excess of 10 years. Their heavy texture is 
derived partly from their composition and partly 
from the method of application, typically by 
means of specially-designed rollers. In addition to 
their use externally, coatings of this type might be 
suitable for internal walls where a hard-wearing 
textured finish is required  
7/10 Masonry paint,  
solvent-borne,  Composition varies considerably.  
Older types can be based on a The appearance of this type of coating is similar 
to that of the 7/8 types, and film thickness is of DRS 554: 2022 
17                ©RSB2023- All rights reserved 
 smooth or fine 
textured  drying-oil/resin type binder, others on 
modified or synthetic rubber film-
formers. Pigmentation is generally as 
for other masonry paints  the same order. Permeability is usually lower, 
and the coating might therefore provide greater 
resistance to penetration by water and other 
agents, and scope for protective use, but it 
should be applied to dry substrates. Brush  
application will generally be slower than with 7/8 
types. It is more tolerant of poor drying  
conditions than water-borne types  
7/11 Masonry paints,  
solvent-borne, thick, 
textured  
 Composition variable but typically 
employs a drying-oil resin binder; can 
be described as polyester (i.e. alkyd). 
Usually contains coarse extender 
and/or fibrous material.  
Pigmentation as for other masonry 
paints  These provide coatings of substantial thickness 
(0.6 mm to 1.0 mm), of relatively low 
permeability, and therefore have good resistance 
to moisture penetration. Coatings of this type are 
usually applied by spray or roller, often by 
specialist contractors.  
Material and application costs are likely to be 
high  
7/12 Silicate-based  
masonry coatings  Water-borne. Based on water soluble 
silicates with possible addition of 
minor quantities of organic resins  The coatings are unusual in being based on an 
inorganic binder. They are suitable for external 
and internal surfaces. They provide inert non 
flammable films which are less affected than 
organic coatings by fungal and algal growth and 
are compatible with all mineral building materials. 
External surfaces to be painted should be free 
from dirt and all previous paint coatings. 
Application can be by brush, roller or spray.  
While drying, the coating can be very susceptible 
to rain damage. The liquid paints are highly 
alkaline (caustic) and hence precautions should 
be taken during application. Resistance to 
moisture penetration can be improved by use of 
a hydrophobic impregnation treatment (e.g. 
silane, siloxanes)  
7/13 Cement paint to  
BS 4764  Based on white Portland cement with 
titanium dioxide or coloured 
pigments, and additives to assist 
application and increase water-
repellence.  
Supplied in powder form and mixed 
with water immediately before 
application  Low-cost coatings giving a rough finish and used 
mainly for exterior wall surfaces, although they 
can be used inside except on gypsum plaster: 
not recommended for application over other 
types of paint. On lengthy outside exposure, 
pastel shades can tend to lighten and darker 
colours to become patchy. Can be used as a 
primer on uncoated exterior wall surfaces prior to 
finishes of type 7/9 or 7/10  
7/14 Multi-colour finish  There are different types of multi-
colour finish. In one type, droplets of 
pigmented resin solution are 
emulsified in an aqueous medium so 
that the coating is water-thinnable. 
The pigmented droplets remain 
discrete in the dry film, so providing 
the multi-colour effect. In another 
type, a pigmented emulsion-type 
basecoat is followed, when dry, by 
spray-applied spatter coats of similar 
material.  
Alternatively, multi-colour patterns 
can be produced.  
Finally, an emulsion-type clear glaze-
coat can be applied. In a third type, a 
pigmented emulsion-type basecoat is  
followed, when dry, by a clear  
emulsion glaze in which are 
suspended multi-coloured flakes of 
solid material  These are quick-drying, hard-wearing finishes for  
interior wall surfaces, often used in circulating 
areas, cloakrooms and similar hard-wear 
locations. Application is usually by spray, but 
materials of the third type might be suitable for 
brush or roller application  
 
7/15 Plastic texture paint  Typically, based on gypsum and This is essentially a decorative coating for interior  
©RSB 2023- All rights reserved                  18 
 supplied as dry powder for mixing 
with water before use, but ready-for-
use water-borne dispersion types are 
available.  
These may be referred to as synthetic 
resin plaster and do not necessarily 
contain gypsum. The term plastic  
indicates that the material can be 
worked after application to provide 
relief texture effects  use only. It can be used as a substitute for 
plaster skimming on plasterboard ceilings or to 
disguise rough or cracked walls and ceilings. 
Texture is achieved either directly by spraying or 
by brush or trowel application and subsequent 
combing, stippling or other treatment.  
Some types are self-coloured and require no 
further treatment; others might require over-
painting, e.g. with a water-borne paint.  
Table 8 – Transparent and semi-transparent finishes for interior wood 
Ref. Description  General composition  Characteristics and usage  
8/1 Solvent-borne clear 
varnish, general  
purpose  Typically drying-oil/alkyd,  
urethane or urethane/alkyd  
resin  Used as a sealer on both softwood and hardwood 
surfaces. Available in a range of gloss from matt 
to full gloss. Some types might be sufficiently 
abrasion resistant for use on hardwood and 
softwood floors, counters and similar hard wear 
locations  
8/2 Water-borne clear 
varnish, general  
purpose  Water-borne acrylic copolymer  Fast drying, durable protective coating for most  
interior wood  
8/3 Water-borne clear 
floor varnish  Water-borne acrylic with  
polyurethane dispersion  High durability interior clear wood lacquer. Ideal 
heavy wear interior wood surfaces especially 
traditional floors. Resistant to common chemicals 
and hot water  
8/4 Semitransparent  
interior wood 
stain/dye  Coloured pigments or dyes, with or 
without drying-oil, water or solvent-
borne  Used essentially to modify or enhance the  
appearance of interior wood without obscuring  
its grain and is usually over coated with a clear  
finish  
8/5 Solvent-borne two 
pack varnish  Typically oil, alkyd or polyol cured 
with aliphatic isocyanate  Limited potlife, some additional safety 
precautions required. Used in hard wearing 
areas, such as flooring  
Table 9 – Transparent and semi-transparent finishes for exterior wood 
Ref. Description  General composition  Characteristics and usage  
9/1 Clear varnish,  
solvent-borne  Typically drying-oil/phenolic or  
alkyd resin  This provides a tough water-resistant coating,  
used principally as a clear protective finish for 
exterior hardwood. Usual mode of eventual failure  
by cracking and flaking, and in exposed situations  
demands frequent maintenance  
9/2 Solvent-borne two 
pack varnish  Typically oil, alkyd or polyol cured 
with aliphatic isocyanate with added 
UV absorber  Limited potlife. Used primarily on hardwoods.  
Similar to some yacht varnishes. Can give  
superior performance on hardwoods  
9/3 Semitransparent  
exterior wood stain, 
low-build, solvent-
borne  Resins, pigments and fungicides in 
organic solvent  
 Relatively thin coating that normally imparts a 
noticeable sheen to the surface. Relatively high 
moisture vapour permeability and wood likely to 
be subject to dimensional movement and surface 
splitting. Not best suited to dimensioned  
components such as joinery  
9/4 Semitransparent  
exterior wood stain, 
low-build, water-
borne  As for 9/3 minimizing the use of  
organic solvents  Relatively thin coating that normally imparts a 
noticeable sheen to the surface. Relatively high 
moisture vapour permeability and wood likely to 
be subject to dimensional movement and surface 
splitting. Not best suited to dimensioned 
components such as joinery  
9/5 Semi-transparent  
exterior wood  
stain, medium build,  
solvent borne  Generally as for 9/3 but higher resin 
content  Often used as top coat for 9/3. Because of its  
higher resin content this type of stain will confer a  
higher build and offers better control of moisture  
and dimensional movement  
9/6 Semi-transparent An alternative to 9/5 minimizing the Often used as top coat for 9/4. Because of its  DRS 554: 2022 
19                ©RSB2023- All rights reserved 
 exterior wood stain, 
medium-build, water-
borne  use of organic solvents.  higher resin content this type of stain will confer a  
higher build and offers better control of moisture  
and dimensional movement  
Table 10 – Bituminous and tar-based coatings 
Ref. Description  General composition  Characteristics and usage  
10/1 Black paint (tar 
based) conforming to  
BS 1070, types A and 
B  Coal-tar or water gas-tar solutions  Moisture-resistant protective coatings for general 
use on metal and other surfaces where 
decorative appearance is unimportant. Both 
types are suitable for cold application, e.g. by 
brush. Type A is required to dry in 8 h and type B 
in 4 h  
10/2 Bitumen-based  
coatings conforming 
to RS EAS 1054, 
types  
1 and 2  Bitumen solutions, type 2 with fillers  Generally as for 10/1. Type 1 without fillers, type 
2 with, permitting greater film thickness per coat. 
Not suitable for use in contact with drinking water 
(see 10/3 for suitable types)  
10/3 Bitumen-based  
coatings conforming 
to RS EAS 1054, 
types  
1 and 2  Bitumen solutions, type 2 with fillers  Generally as for 10/2, but suitable for use in 
contact with drinking water.  
10/4 Bituminous emulsion  Water-borne bitumen emulsion  Black, water-thinnable moisture-resistant coating.  
Typical use is as a waterproof membrane on  
exterior walls before application of water-borne  
masonry paints  
Title 11 – Specialist coatings 
Ref. Description  General composition  Characteristics and usage  
11/1 Two-pack epoxy  
primers, undercoats 
and finishes  Epoxy resin binder with amine or 
amide curing agent.  
Pigmentation according to end use, 
e.g. metal primers usually contain 
corrosion inhibitive pigments 
Primers are generally either zinc rich 
or zinc phosphate pigmented.  
Undercoats often contain MIO 
pigments. Both solvent-borne and 
water-borne epoxy coatings are 
available  Resistant to some acids and weak alkalis, oils, 
solvents and abrasion and used for protection of 
surfaces, especially steelwork, in severe 
conditions where coatings of conventional type 
are inadequate. Should be applied only to stable, 
well-prepared surfaces. Blast cleaning of 
steelwork is essential. Might not be suitable for 
application to gypsum plaster; a cement plaster 
base is preferable. Application to substrates 
liable to significant dimensional change (e.g. 
external woodwork) can result in cracking of the 
film. Curing is temperature-dependent, and the 
manufacturer’s recommendations in respect of 
ambient and surface temperatures should be 
observed. High humidity during application and 
curing can also affect the coatings  
11/2 Two-pack coal tar  
epoxy coatings  
Replaced by  
hydrocarbon epoxies  Binder blended with hydrocarbon 
resins and mineral extenders  General characteristics as 11/1 but lower 
resistance to solvents. Main use is for protection 
in conditions of very high humidity or immersion 
in fresh or seawater  
11/3 Two-pack 
polyurethane  
pigmented coatings,  
principally finishes  Acrylic modified polyester resin 
binder with polyisocyanate curing 
agent and white or coloured 
pigments  General characteristics as 11/1, but low 
temperature curing is usually better and 
sensitivity to moisture curing greater than with 
epoxies. Principal usage is as non-yellowing 
chemical-resistant finishes over epoxy primers 
and undercoats. These products contain  
isocyanates and need to be handled in 
accordance with relevant HSE requirements 
11/4 One-pack moisture-
curing polyurethane  
primers, undercoats Polyether isocyanate binder.  
Pigmentation according to end use  Resistant to some acids and weak alkalis, oils, 
solvents and abrasion; and used for the 
protection of steel and concrete surfaces in  
©RSB 2023- All rights reserved                  20 
 and finishes  severe conditions where coatings of conventional 
type are inadequate. Apply only to stable, well 
prepared surfaces. Blast-cleaning of steelwork is 
essential. Might not be suitable for application on 
gypsum plaster; a cement plaster base is 
preferable. The film might crack if applied to 
substrates liable to significant dimensional 
change (e.g. external woodwork). Curing is 
humidity-dependent and to some extent 
temperature-dependent. Observe the 
manufacturer’s recommendations in respect of 
humidity and temperature. Most formulations can 
tolerate traces of surface moisture  
11/5 Acrylated rubber  
primers, undercoats 
and finishes  Acrylated rubber, pigmented  
according to end use, as 11/1. Some 
types can be modified with drying-
oil/alkyd resin. Formulations yielding  
coatings of substantial thickness are 
available Suitable for use on most substrates and, as one-
pack products, are more convenient to use than 
two-pack epoxy and polyurethane coatings, 
although their chemical resistance might be 
lower. As for solution binders (see F.2.5), drying 
is essentially by evaporation and is less affected 
by low temperatures than is that of drying-oil/ 
resin, epoxy and polyurethane coatings.  
Brush or roller application to large areas might be  
difficult, and spraying is recommended (see 9.3)  
11/6 Cellulose coatings, 
clear or pigmented,  
other than cellulose 
multicolor types 
(7/14)  Nitrocellulose/synthetic resin  
solutions clear or pigmented  Quick-drying coatings, having a limited 
application in the painting of buildings. As with 
other lacquers (see F.2.5) cellulose coatings are 
best applied by spray, although some types can 
be modified to allow brush applications to small 
areas. The most frequent usage is of clear and 
pigmented coatings, including “gold” and 
“bronze” lacquers for shop fronts, lift doors, 
ornamental metalwork and similar items, work 
usually carried out by specialists.  
 
NOTE – This material has a high fire risk  
Table 12 – Coating systems for interior wood 
Application (end -
use) Coating type (see note 
1) Priming options for new and 
bare areas of wood (see also 
8.1.6.3, 8.2.2.3 and table 3) Typical life to first 
maintenance (see note 2) 
Opaque systems 
Internal surfaces of  
door and window  
joinery, wood trim,  
plywood and wood 
based boards  General purpose  
pigmented finishes as  
described in 7/1, 7/2, 7/3  
and 7/4  
 Opaque primer 3/1 optionally  
over coated with undercoats  
6/1 or 6/2  Over 5 years  
Transparent and semi -transparent systems  
Internal surfaces of door 
and window joinery, 
wood trim, plywood and 
woodbased boards  Varnish, clear or 
semitransparent in wood 
tone of choice. Build and 
gloss level of choice. 
Abrasion resistant binder, 
e.g. polyurethane, for 
hardwear situations (Table 
8)  Often primed with a suitably 
diluted coating of the finishing 
coat. Wood stains  
may be used to enhance  
grain  Variable according to  
type and service  
conditions but typically up  
to 5 years in average  
wear conditions  
Interior wood stain in  
wood tone of choice,  
possibly over-coated with 
clear varnish   Variable according to  
type and service  
conditions but typically up  
to 5 years in average wear 
conditions. Might  
give lifetime service in  
some situations  DRS 554: 2022 
21                ©RSB2023- All rights reserved 
 Flooring  Varnishes with good 
abrasion resistance. See  
8/1 and 8/3. Specialist  
application may be  
required  Often primed with a suitably  
diluted coating of the finishing 
coat. Wood stains may be 
used to enhance grain  Long life in domestic situations 
but will require maintenance in 
high traffic areas  
 
Note 1 – Wood coatings are described by many terms including colour, build and opacity. Systems that do not fully 
obliterate the colour or grain of wood are sometimes described as natural finishes. Coating systems can be based on 
different chemistries, e.g. alkyds and acrylics, and can be carried in either water or solvent. For interior use the latter are 
being phased out in response to environmental legislation.  
Note 2 – Interiorcoatings will not require frequent maintenance unless mechanically damaged. Transparent wood coatings 
could have some colour change.  
Table 13 – Coating systems for exterior wood 
Application (end -
use) Coating type (see note 
1) Priming options for new and 
bare areas of wood (see also 
8.1.6.3, 8.2.2.3 and table 3) Typical life to first 
maintenance (see note 2) 
Opaque systems 
Exterior door and  
window joinery  1 or 2 coats general-
purpose alkyd-based 
gloss paint over 
recommended undercoat  Opaque solvent-borne or  
water-borne (3/2 or 3/4), or  
preservative primer (3/6)  3 to 5 years  
1 or 2 coats flexible 
exterior alkyd-based paint 
over recommended 
primer. Gloss level and 
colour of choice  Opaque solvent-borne or 
water-borne (3/2 or 3/4), or 
preservative primer (3/6).  
Special primer/undercoats may 
be specified.  Over 5 years  
1 or 2 coats exterior 
waterborne paint (7/3). 
Gloss level and colour of 
choice  Opaque solvent-borne or  
water-borne (3/2 or 3/4), or  
preservative primer (3/6)  Over 5 years  
Softwood and plywood 
for cladding, 
bargeboards, soffits and 
fascias  1 or 2 coats flexible 
exterior alkyd-based paint 
over recommended 
primer. Gloss level and 
colour of choice  Opaque solvent-borne or  
water-borne (3/2 or 3/4), or  
preservative primer (3/6)  Over 5 years  
 
1 or 2 coats exterior 
waterborne paint (7/3). 
Gloss level and colour of 
choice  Opaque solvent-borne or  
water-borne (3/2 or 3/4), or  
preservative primer (3/6)  Over 5 years  
NOTE 1 – Wood coatings are described by many terms including colour, build and opacity. Systems that do not fully 
obliterate the colour or grain of wood are sometimes described as natural finishes. Coating systems can be based on 
different chemistries, e.g. alkyds and acrylics, and can be carried in either water or solvent. For interior use the latter are 
being phased out in response to environmental legislation.  
 
NOTE 2 – Interior coatings will not require frequent maintenance unless mechanically damaged. Transparent wood 
coatings could have some colour change. 
Table 13 – Coating systems for exterior wood (continued) 
Application (end use)  Coating type  
(see Note 1)  Priming options for new and 
bare areas of wood (see also 
8.1.6.3, 8.2.2.3, and Table 3)  Typical life to first 
maintenance  
(see Note 2)  
Transparent and semi -transparent systems (see Note 3)  
Exterior softwood door  
and window joinery  Exterior wood stain  
Medium-build (9/5 or 9/6)  3/6 or 3/3  Depends on product type, 
unlikely to exceed 2 to 3 years 
on full exposure  
Exterior hardwood door  
and window joinery  
(see Note 4)  Exterior wood stain  
Medium-build (9/5 or 9/6)  3/6 or 3/3  Typically 3 to 5 years  
Depending on exposure   
©RSB 2023- All rights reserved                  22 
 Exterior grade plywood,  
e.g. door panels  Exterior wood stain  
Medium-build (9/5 or 9/6)  3/6 or 3/3  Depends on product type, 
unlikely to exceed 2 to 3 years 
on full exposure.  
Efflorescence is a risk factor  
External softwood  
boarding, cladding,  
bargeboards, soffits,  
fascias  Exterior wood stain Low 
build (9/3 or 9/4)  
Medium build (9/5 or 9/6)  
 3/6 or 3/3  
 3 to 5 years depending  
on exposure  
External hardwood  
boarding, cladding,  
bargeboards, soffits,  
fascias  Exterior wood stain  
Medium-build (9/5 or 9/6)  3/6 or 3/3  4 to 5 years depending on 
exposure  
External grade plywood  
boarding, cladding,  
bargeboards, soffits,  
fascias  Exterior wood stain  
Medium-build (9/5 or 9/6)  3/6 or 3/3  
 Typically 3 to 5 years 
depending on exposure.  
Efflorescence is a risk factor  
Gates, fences,  
handrails, decking and  
garden furniture (see  
Note 5)  Exterior wood stain  
Medium-build ((9/5 or 9/6)  
Low-build (9/3 or 9/4) (see  
Note 3)  3/6 or 3/3  3 to 5 years  
NOTE 1 – Woodcoatings are described by many terms including colour, build and opacity. Systems, which do not fully 
obliterate the colour or grain of wood, are sometimes described as natural finishes or exterior wood stains. Coating 
systems can be based on different chemistries, e.g. alkyds and acrylics, and can be carried in either water or solvent.  
 
NOTE 2 – Lifeexpectancies shown assume application to dry, sound timber which, if necessary, has received preservative 
treatment and are based on performance in moderate environments as defined in Table 2. Lifetime expectations are 
expressed as an average and a distribution (standard deviation) around the average can be expected in real situations. 
ISO 16053 provides a performance specification for exterior wood coatings. 
 
NOTE 3 – Thefinal appearance of transparent and semi-transparent coatings will depend on the number of coats. Two is 
the usual minimum; an additional coat will increase service life but may darken the appearance. Penetrating low-build 
stains are primarily used on rough sawn timber where one or two coats are required. 
 
NOTE 4 – Commercialsystems designed for hardwood might have a different composition to their softwood counterparts. 
 
NOTE 5 – Commercialvariants might include different degrees of water repellence.  
Table 14 – Paint systems for iron and steel except heated surfaces 
Surface condition,  
primer and reference  
in Table 4  Finishing system and  
references in Table 6 and Table 
7  Total film thickness μm  
 Typical life to first  
maintenance in exposure 
conditions indicated (see 
Note 1)  
Manually cleaned  
2 coat primer, e.g. 4/5  2 coats aluminium paint (7/6);  
or  
1 coat solvent-borne undercoat 
(6/1) and 1 coat alkyd gloss finish 
(7/1)  
or  
2 coats of gloss finish;  
or  
2 coats micaceous iron oxide 
(MIO) paint (7/7 high-build type) 
(see Note 3)  125 to 150  
 Interior  
Up to 10 years  
1 coat primer, e.g. 4/5  2 coats aluminium paint (7/6);  
or  
1 coat solvent-borne undercoat  
(6/1) and 1 coat alkyd gloss finish  85 to 115  Interior  
Up to 5 years  DRS 554: 2022 
23                ©RSB2023- All rights reserved 
 (7/1) or 2 coats of gloss finish;  
or  
2 coats micaceous iron oxide  
paint (7/7 high-build type) (see  
Note 3)  Exterior  
Not recommended  
Blast-cleaned  
2 coats oil-primer, e.g. 
4/5  1 coat solvent-borne undercoat  
(6/1) and 2 coats alkyd gloss  
finish (7/1) or 2 undercoats and 1  
coat of gloss finish (see Note 2);  
or  
2 coats micaceous iron oxide  
paint (7/7 high-build type) (see  
Note 3)  170 to 205  Interior  
Over 10 years  
Exterior  
Up to 10 years  
1 coat primer, e.g. 4/5  1 coat solvent-borne undercoat  
(6/1) and 2 coats alkyd gloss  
finish (7/1);  
or  
2 undercoats and 1 coat of gloss  
finish (see Note 2);  
or  
2 coats micaceous iron oxide  
paint (7/7 high-build type) (see  
Note 3)  115 to 145  Interior  
Up to 10 years  
Exterior  
Up to 5 years for film  
thicknesses exceeding  
125 μm  
NOTE 1 – Lifeexpectancies are based on performance in moderate exposure conditions as defined in Table 2.  
 
NOTE 2 – Mid-sheenalkyd finish (7/3) can be used in mild interior exposure conditions.  
 
NOTE 3 – MIOpaint can be covered with alkyd gloss finish (if manufacturer approves) to provide specific colour.  
 
NOTE 4 – Zinc rich primers (e.g. 4/7) are also used but problems can arise with many or drying-oil/resin systems, advice 
needs to be sought regarding compatible top coats (see also 11.3.2).  
Table 15 – Site pre-treatment and priming of non-ferrous metals and stainless steel (not factory pre-
treated) 
Substrate  Surface preparation and pretreatment/priming  
Aluminium, smooth surfaces, e.g.  
sheets, extrusions and aluminized  
steel  Degrease (see 8.4.2.2). Abrade (see 8.4.2.7) and/or apply treatment primer 
(4/4). Then prime using zinc phosphate (4/5)  
Aluminium, rough surfaces, e.g.  
castings and sprayed metallic  
coatings  Abrade lightly (see 8.4.2.7) remove dust and dirt. Sprayed metallic coatings 
might require washing (see 8.4.2.3). With sprayed metallic coatings, pre-
treatment primer (4/4) should be applied immediately following application of the 
coating (see 8.4.3.4). Then prime using zinc phosphate (4/5)  
Zinc sheet, zinc (hot-dip galvanized,  
sherardized and electroplated) coated 
steel, zinc aluminium alloy (hot dip) 
coated steel  Degrease (see 8.4.2.2); abrade coated sheet metal components as necessary 
(see 8.4.3.3); apply pre-treatment primer (4/4) or treat with mordant solution 
(4/3). With sherardizing or if suitable primer is used on other coatings, 
weathering or application of pre-treatment primer is not needed. Some hot dip 
coatings might need de-nibbingA) and careful abrasion to remove surface 
deposits and sharp points  
Zinc and zinc aluminium alloy, sprayed  Sprayed metallic coatings might require washing (see 8.4.2.3). Apply pre-
treatment primer (4/4) or treat with mordant solution (4/3). With sprayed metallic 
coatings, this should immediately follow application of the coating (see 8.4.3.4). 
If painted at a later time first remove dust and dirt; wash surface if necessary  
Copper, brass, bronze  Degrease (see 8.4.2.2). Abrade lightly (see 8.4.2.7) or apply pretreatment 
primer (4/4)  
Lead  Abrade WET (see 8.4.2.7 and for health and safety guidance, see B.1.2). Apply 
pre-treatment primer (4/4)  
Cadmium coatings  Degrease (see 8.4.2.2). Abrade lightly (see 8.4.2.7). Apply pretreatment  
primer (4/4)  
Tin coatings  Degrease (see 8.4.2.2). Abrade lightly (see 8.4.2.7)  
Chromium and nickel coatings (if  Abrade (see 8.4.2.7) to remove corrosion products. Apply pretreatment   
©RSB 2023- All rights reserved                  24 
 corroded)  primer (4/4)  
Stainless steel (see 8.3.2.2)  Degrease (see 8.4.2.2). Abrade (see 8.4.2.7). Apply pre-treatment primer (4/4)  
A) De-nibbing should take place before delivery to site. If this does not happen, it is essential that de-nibbing takes place 
prior to painting.  
 
NOTE 1 – Forspecialist advice on substrates listed in this table, check with the coatings manufacturer.  
 
NOTE 2 – Abrasionof metals may detract from the aesthetic appearance of the overall finish.  
Table 16 – Coating systems for internal plaster, concrete, brick, block and stone 
Substrate  
condition  Finish type and 
reference in Table 7  Primer and reference in Table 5  Coating system and references in 
Table 6 or Table 7  
DRY r.h.  
below 75%  
(see Note 1)  Gloss, mid-sheen or  
matt (7/1, 7/2, 7/3)  Alkali-resisting primer (5/1) or, 
plaster only, water-borne primer 
(5/2)  Gloss finish: 1 coat solvent-borne (6/1) 
or  
water-borne (6/2) undercoat; 1 coat 
alkyd gloss finish (7/1)  
or  
1 coat water-borne (7/2)  
Mid-sheen finish:  
2 coats alkyd mid-sheen finish (7/1) or 
2 coats water-borne (7/2)  
Matt-finish:  
2 coats alkyd matt finish (7/3) or 2 
coats water-borne (7/4)  
General purpose  
emulsion paint (7/4, 
7/5)  Primer not usually required but 
see 8.5.1.4 and 8.5.1.5. A well 
thinned first coat of water-borne 
paint might be required on 
surfaces of high or variable  
porosity (see 8.6.2.4)  Matt or mid-sheen finish: 2 or 3 coats  
general purpose water-borne paint, 
matt or mid-sheen (7/4)  
Matt, high-opacity finish: 2 coats 
contract water-borne paint (7/5) 1 coat, 
spray applied, might suffice in some 
situations  
Multi-colour (7/14)  Primer or basecoat as  
recommended by manufacturer  Usually 1 coat multi-colour finish (7/14)  
spray-applied but refer to 
manufacturer’s instructions  
Textured (7/15)  Primer not usually required but 
refer to manufacturer’s  
instructions  Plastic texture paint (7/15): Normally 1 
coat  
but might require over-painting  
Water-borne masonry paint, heavy-
texture (7/9):  
Normally 1 coat but refer to 
manufacturer’s instructions  
Masonry paint,  
mineral type (7/12)  Check with manufacturer  Check with manufacturer  
Cement paint (7/13)  
(not on gypsum 
plaster)  Primer not required  1 or 2 coats cement paint (7/13)  
DRYING  
Some damp  
patches might  
be evident, r.h.  
75% to 90%  Water-borne paint  
(7/4, 7/5)  
 As for DRY substrates  Matt or mid-sheen finish:  
2 or 3 coats general purpose water-
borne paint, matt or mid-sheen (7/4)  
Matt, high-opacity finish: 2 coats 
contract water-borne paint (7/5) 1 coat, 
spray applied, might suffice in some 
situations  
Multi-colour finishes  
(7/14) possible but  
consult manufacturer  As for DRY substrates  Usually 1 coat multi-colour finish (7/15)  
spray-applied but refer to 
manufacturer’s instructions  
Textured paints (7/15) 
possible but consult  
manufacturer  As for DRY substrates Plastic texture paint (7/15):  
Normally 1coat but might require 
overpainting  
Water-borne masonry paint, heavy 
texture (7/9):  
Normally 1 coat but refer to  DRS 554: 2022 
25                ©RSB2023- All rights reserved 
 manufacturer’s instructions  
If over coating is necessary, water-
borne paint should be used  
Masonry paint, mineral 
type (7/10)  Check with manufacturer  Check with manufacturer  
Cement paint (7/11)  
(not on gypsum 
plaster)  Primer not required  1 or 2 coats cement paint (7/13)  
DAMP  
Obvious damp 
patches, r.h.  
90% to 100%  Water-borne paint  
(7/4, 7/5) possible, but  
consult coating  
manufacturer  Primer not recommended  Matt or mid-sheen finish:  
2 or 3 coats general purpose water-
borne paint, matt or mid-sheen (7/4)  
Matt, high-opacity finish:  
2 coats contract water-borne paint (7/5) 
1 coat, spray-applied, might suffice in 
some situations  
Contract types (7/5) are usually more  
permeable than general purpose (7/4)  
types and less prone to failure on damp  
substrates  
Masonry paint, mineral 
type (7/12)  Check with manufacturer  Check with manufacturer  
Cement paint (7/13)  
(not on gypsum 
plaster)  Primer not required  1 or 2 coats cement paint (7/13)  
WET  
Moisture visible 
on surface, r.h.  
100%  Cement paint (7/13)  
(not on gypsum  
plaster)  Primer not required  1 or 2 coats cement paint (7/13)  
NOTE 1 – For information on the repair of concrete structures, see ISO 16311 (Parts 1 - 4)ISO 16311 (from Part 1 to part 4). 
 
NOTE 2 – For information on the selection of coating systems for exterior masonry and concrete, see ISO 7783)..  
 
NOTE 3 – r.h. refers to the relative humidity in equilibrium with the surface. See 8.5.1.1 for method of measuring moisture content.  
Table 17 – Coating systems for external renderings, concrete, brick, block and stone 
Substrate  
condition  Coating type  Primer and reference 
in Table 5  Coating system and 
references in Table 6 or 
Table 7 and use  Typical life to first 
maintenance  
(see Note 2)  
DRY r.h.  
below 75%  
(see Note 1)  Masonry paints,  
solvent-thinned  
(7/10 or 7/11)  Alkali-resisting primer 
(5/1) or as 
recommended by  
manufacturer  Smooth or fine-textured 
(7/10) types, solvent-
thinned 2 coats  5 years or more  
Thick, textured (7/11) 
types, solvent-thinned  
10 years or more  
Usually 1 or 2 coats applied 
by spray, often by specialist  
applicators  10 years or more  
Water-borne masonry 
paints (7/8, 7/9)  Primer not usually  
required with 7/8 types 
but see 8.5.1.4 and 
8.5.1.5  Smooth or fine-textured 
(7/8)  
water-borne types 2 coats  5 years or more  
Primer not usually  
required with 7/9 types 
but refer to  
manufacturer’s  
recommendations  Heavy-textured (7/9) 
waterborne type Usually 1 
coat applied by roller  10 years or more  
Masonry paint,  
mineral type (7/12)  Check with  
manufacturer  Check with manufacturer  Over 15 years  
Cement paint (7/13)  Primer not required  2 coats cement paint (7/13)  3 to 5 years  
Alkyd gloss and  
modified alkyd gloss 
(7/1)  Alkali-resisting  
Primer (5/1)  1 coat solvent-borne  
undercoat (6/1); 1 or 2 
coats alkyd gloss finish 3 to 5 years   
©RSB 2023- All rights reserved                  26 
 (7/1)  
DRYING  
Some damp  
patches might 
be visible, r.h.  
75% to 90%  Water-borne  
masonry paints  
(7/8 or 7/9)  As for DRY substrates  Smooth or fine-textured 
(7/8)  
water-borne type 2 coats; 
or  
Heavy-textured (7/9) 
waterborne types Usually 1 
coat applied by roller  Potentially as for DRY 
substrates but some 
risk of earlier failure at  
higher moisture levels  
Masonry paint,  
mineral type (7/12)  Check with 
manufacturer  Check with manufacturer  Over 15 years  
Refer to 
manufacturer’s  
recommendations  
for use of 
solventborne  
masonry paints (7/10 
or 7/11)  As for DRY substrates  Smooth or fine-textured 
(7/10) types, solvent-borne 
2 coats; or Thick, textured 
(7/11) types, solvent-borne 
Usually 1 or 2 coats applied 
by spray, often by specialist 
applicators  Potentially as for DRY 
substrates but some 
risk of earlier failure at  
higher moisture levels  
DAMP  
Obvious Damp 
patches, r.h. 
90% to 100%  
 Masonry paint,  
mineral type (7/12)  Check with  
manufacturer  Check with manufacturer  Over 15 years  
Cement paint (7/13  Primer not required  2 coats cement paint (7/13)  As for DRY 
substrates  
Refer to  
manufacturer’s  
recommendations  
regarding use of  
water-borne masonry 
paints (7/8 or 7/9)  Primer not required  Smooth or fine-textured 
(7/9) water-borne types 2 
coats; or Heavy-textured 
(7/10) waterborne types 
Usually 1 coat applied by 
roller  Potentially as for DRY  
substrates but high  
risk of earlier failure  
WET  
Moisture visible 
on surface r.h.  
100%  Cement paint (7/13)  Primer not required  2 coats cement paint (7/13)  As for DRY  
substrates but some  
risk of earlier failure  
NOTE 1 – r.h. refers to the relative humidity in equilibrium with the surface. See 8.5.1.1 for method of measuring moisture content.  
 
NOTE 2 – Life expectancies shown assume application to dry, sound substrates, qualified as indicated for other substrate conditions, and 
are based on performance in moderate external conditions as defined in Table 2. Aesthetic considerations might influence the need for 
maintenance.  
 
NOTE 3 – For information on the repair of concrete structures, see ISO 16311 (from Part 1 to part 4).ISO 16311 (Parts 1 - 4).  
 
NOTE 4 – For information on the selection of coating systems for exterior masonry and concrete, see ISO 7783. 
Table 18 – Site priming of fibre building board, wood chipboard and plaster board (not factory-primed 
or sealed) 
Type of board or sheet  Primers and references in Table 3 and Table 5  
With solvent-borne finishes  With water-borne finishes A)  
Hardboard, medium board, medium 
density fiberboard (MDF) and soft 
board  Primer-sealer (5/3)  
Water-borne primer (5/2)  
Aluminium wood primer (3/2)  Not usually required, but, for 
absorbent board, first coats might 
need additional thinning  
Flame retardant treated  Alkali-resisting primer (5/1)  Alkali-resisting primer (5/1)  
Soft board, bitumen-impregnated  Aluminium wood primer (3/2)  Not usually required  
Wood chipboard  Solvent-borne wood primer (3/1)  
Primer-sealer (5/3)  
Water-borne primer (5/2)  
Aluminium wood primer (3/2)  Not usually required except possibly  
that solvent-borne primer (3/1, 3/2 or  
5/3) is recommended for single layer  
boards (see 8.2.1.3) to prevent  
swelling of chips  
Plasterboard  Primer-sealer (5/3)  
Water-borne primer (5/2)  Not usually required (see Note)  
Oriented Strand Board (OSB)  As wood chipboard  As with solvent-borne finishes if a  
high quality finish is required  
Cement bonded particleboard  Water-borne primer (5/2)  
Alkali-resisting primer (5/1)  Water-borne primer (5/2)  
Alkali-resisting primer (5/1)  
Water-borne multi-colour finishes (7/14) are usually applied over a special base coat.  
 DRS 554: 2022 
27                ©RSB2023- All rights reserved 
 NOTE – Refer to the plasterboard manufacturer's recommendations on priming for use with water-borne finishes.  
Table 19 – Paint film defects arising during, or shortly after application 
S/N Defect name  Possible cause  Cure 
1 Bleeding Solvent or water reactive stain, timber 
extractives, nicotine, tar or bitumen Remove as much contamination as 
possible, seal with stain block primer,  
alkali resisting primer or aluminium 
wood primer  
2 Blooming, or milky appearance 
usually gloss paint, also slight 
matting of the gloss  Cold temperatures, high humidity 
and/or moisture, during the drying 
process of the paint. Usually  
associated with winter months  Abrade and re-coat  
3 Ropiness (brush marks)  Poor flow of the paint, over brushing, 
rapid drying, etc.  Abrade and re-coat  
4 Cissing (separation of paint  
film whilst wet)  Surface contamination, wax, grease, 
sometimes occurs when applying 
water-borne paint over poorly 
prepared oil-based paint  Remove as much contamination as 
possible, degrease, use a silicone 
digester, abrade and re-coat.  
Ensure application tool is also free from 
contamination  
5 Sleepy gloss (low sheen)  Sinkage into substrate, due to  
incorrect or insufficient primer or  
undercoat, medium density fibre 
board paraffin wax contamination  For medium density fibre board, abrade 
and then apply acrylic primer 
conforming to BS 7956, then re-coat. 
Other surfaces may simply require  
re-coating  
6 Flashing (halo effect where 
two edges of paint meet)  Losing the wet edge of the paint  
during application, trying to “touch up” 
areas, especially sheen paints, but 
can occur with all paints  Re-paint to the nearest whole elevation, 
ensuring the wet edge is maintained  
 
7 Curtains, runs, sagging,  
floatation of pigment  Over application, i.e. too much paint  
applied unevenly  Allow excessively thick areas to harden 
(sometimes scraping off excess 
thickness will be required). Abrade and 
re-coat  
8 Cracking/crazing  Usually associated with applying a  
fairly brittle paint over a highly flexible 
layer, i.e. matt over silk  Abrade, correctly prime, i.e. alkali 
resisting primer and recoat.  
Severe instances may require lining 
paper  
9 Pickling (looks like wrinkling)  Solvent attack, i.e. applying  
chlorinated rubber paint over a  
conventional paint, solvents act as a  
stripper  Complete removal of all affected 
coatings may be required  
 
10 Wrinkling, rivelling, shrivelling  Application too thick, usually gloss 
paints, the paint layer skins over but 
remains wet underneath. Can also  
be caused by over coating before  
previous layer is dry  Allow affected areas to harden, abrade 
with wet and dry abrasive paper to 
smooth, and re-coat  
11 Rain spotting (also known as  
pitting)  Rain/water attack during the drying  
phase  Wet abrade to smooth, re-coat  
12 Bittiness  Contaminated paint, dusty 
atmosphere, substrate not clean,  
application tool not clean  Abrade, re-coat, ensure application 
tools are clean, strain the paint  
13 Orange peel effect  Application by roller without laying the 
paint off with a brush (such as 
applying gloss to doors). Poor 
atomization when spraying  Wet abrade to smooth, re-coat using 
correct method and adjustment   
©RSB 2023- All rights reserved                  28 
 Table 20 – Paint film defects arising after a period of exposure 
S/N Defect Typical causes  Remedial treatment  
1 Adhesion failure  a) Application to damp, dirty or  
weather-degraded substrates,  
substrates contaminated by biological  
growth; or subsequent entry of  
moisture, e.g. through open joints in  
woodwork  Flaking, peeling or poorly adhering coating 
should be removed (see 11.5.2) and any 
damaged substrate repaired (see 8.1.4.2). 
Biological growths should be removed (see 
11.5.8). Where moisture is the cause, it should 
be ensured that the substrate is dry before 
repainting. See 8.1.3 in relation to sources of 
moisture in woodwork 
  b) Failure to prepare or pre-treat 
nonferrous metals  Defective material should be removed.  
See 8.4.2 for preparation of non-ferrous metals  
  c) Omission of primer or use of  
unsuitable primer  Defective material should be removed.  
Refer to appropriate substrate in Clause 8 for 
information on priming  
  d) Application to powdery or friable  
substrates  Defective material should be removed.  
Application of a penetrating primer or sealer 
might be necessary (see 11.5.5)  
  e) Application to hard, dense  
substrates, e.g. glass or glazed  
surfaces  Defective material should be removed.  
See 8.14 for subsequent preparatory treatment  
  f) Apparent loss of adhesion on iron  
and steel, might be due to  
detachment of millscale  Removal of millscale, e.g. by blast cleaning  
or flame cleaning, might be impracticable as a 
maintenance operation and is costly, hence the 
desirability of effective initial preparation. There 
might be no alternative to manual cleaning to 
remove millscale as it loosens, but this might 
extend over several repaints  
2 Blistering  Blistering is usually indicative of liquid 
or vapour beneath the coating. The 
presence of water is a frequent 
cause. On painted woodwork, 
migration of water vapour from the 
inside of a building through the wood 
can cause blistering if the internal and 
external coatings do not provide the  
recommended differential 
permeability system. Resinous knots  
might also cause localized blistering  Depending upon the extent and severity of 
blistering, preparation might be confined to 
removal of isolated blisters or complete 
stripping might be necessary. Where moisture 
is the cause, time should be allowed for drying 
out. (See also 8.1 in relation to sources of  
moisture in woodwork.)  
Blistering on resinous external woodwork might 
be influenced by choice of finishing colour  
3 Chalking, powdering  Slow erosion and chalking on lengthy 
exposure, especially externally, is a 
characteristic of many paints and 
wood finishes. It is not usually 
regarded as a defect unless it occurs 
prematurely and profusely, when the 
causes might be as follows:  
a) conditions of exposure 
exceptionally severe;  
b) earlier coats in system have failed 
to satisfy porosity of substrate;  
c) incorrect or unsuitable formulation  In absence of other defects, lightly chalking 
surfaces might require only washing and light 
abrasion to provide a satisfactory base for 
further coats.  
Heavily chalked or powdery surfaces will 
require more vigorous cleaning or abrasion 
combined if necessary with application of a 
penetrating primer (see 11.5.5)  
 
4 Colour defects, e.g. 
fading, staining, 
bleeding, or other 
forms of discoloration  a) Some loss of colour of paint might 
occur on lengthy exposure to bright 
sunlight but is not usually significant.  
Early loss of colour might be due to 
use in unsuitable conditions, e.g. 
external use of a colour intended only 
for interior use.  
Chemical attack might cause change 
or loss of colour  If necessary, consult manufacturer regarding 
selection of colours or types of finish for 
repainting  
b) Solvent-borne finishes tend to 
yellow in situations where direct Yellowing is not usually sufficiently marked to 
be significant. If freedom from yellowing is DRS 554: 2022 
29                ©RSB2023- All rights reserved 
 daylight is excluded. This is more 
obvious with white and light-coloured 
finishes  important, consult manufacturer for guidance 
on selection of oil-free coatings  
c) Apparent colour change might be 
due to masking of colour by surface 
chalking (item 3 of this table) to 
efflorescence (see 8.5.1.2) especially 
on external rendering or, on external 
plywood treated with wood stain, to 
diffusion of water-soluble salts  
contained in adhesives  Normal cleaning usually removes surface 
deposits. Efflorescence and diffusion of salts 
on plywood might recur until source is 
exhausted  
d) Failure of clear finishes on  
external woodwork might result in 
discoloration of exposed wood  Clear finish should be removed completely. 
Sanding or scraping might remove 
discoloration or damaged timber, but 
application of coloured wood stain might be  
necessary to achieve uniform appearance  
e) Constituents of the substrate or  
previous coatings can cause  
discoloration (see 8.5.1.5 and  
11.5.9)  See 8.5.1.5 and 11.5.9  
5 Cracking, other than  
that due to structural  
movement  Cracking is usually indicative of 
stresses within the coating film, 
caused, for example, by applying 
hard-drying coatings over soft 
coatings. It might also be the initial 
stage in adhesion failure (item 1 of 
this table).  
Cracks might be confined to the 
finishing coat or extend through  
the thickness of the film  If cracking is slight and confined to the finishing 
coat, light abrading might provide a satisfactory 
base for recoating. If cracking is severe or 
extends through the thickness of the film, 
complete removal might be necessary 
6 Damage to coating  a) Mechanical damage, e.g. by 
abrasion, impact or vigorous cleaning  
b) Graffiti  Where surfaces are subject to hard wear, 
specialist coatings might be required (see 
4.6.4.6.2).  
Consideration should also be given to the use 
of wear-resistant materials, e.g. ceramic tiles or 
plastics, where practicable. In relation to graffiti, 
see 4.6.4.8  
7 Gloss, loss of  Some loss of gloss is to be expected 
after lengthy exposure, especially 
externally, and might be the first 
stage in chalking (item 3 of this table). 
Where it occurs prematurely, possible  
causes are as described for  
premature chalking  Loss of gloss in the absence of other defects is 
not usually significant in relation to 
maintenance treatment  
8 Biological growths, i.e.  
moulds, algae, lichen,  
moss, blue stain  See 4.6.4.4 and 11.5.8  See 4.6.4.4 and 111.5.8. Consider  
modifications to design or environment which 
might eliminate or reduce causes of failure  
9 Rust-spotting or rust 
staining on painted 
iron and steel  This usually indicates that the 
thickness of the paint system is 
insufficient to provide protection on 
peaks and edges. It might result from 
application of an inadequate system 
initially or at the last repaint or from 
erosion of the film during exposure. A 
further possible cause is failure to use 
a rust-inhibitive primer (see F.4.5 and 
Table 4)  Depending upon the severity and extent of the 
defect, treatment might range from manual 
cleaning and priming of localized areas to 
overall removal of the coating and treatment as 
for new iron and steel (see 8.3).  
Consideration should be given to increasing the 
film thickness of the system or to reducing the 
intervals between repaints until an adequate 
thickness has been built up  
 
5 Organization of work 
5.1 General  
©RSB 2023- All rights reserved                  30 
 5.1.1 Where applicable, painting work should be planned in relation to the work of other trades (see 5.3), to 
ensure that surfaces are in a fit condition to be painted and that completed work is not damaged by 
subsequent building operations; in particular, time should be allowed for drying out of plaster and similar 
surfaces before they are painted. 
5.1.2 In factories and commercial buildings, it might be necessary for work to proceed without interrupting 
the normal functions of the building. This should be planned carefully to avoid inconvenience to the occupants 
and minimize loss of productive time by the contractor. In such circumstances, it might be necessary to erect 
temporary partitioning to isolate the areas where painting is in progress. 
5.2 Health and safety 
The recommendations of Annex B should be followed, concerning the manner of dealing with typical hazards 
to health and safety that might be encountered in the painting of buildings. 
Information on the properties or constituents of coatings or other materials that affect health and safety should 
be obtained from the manufacturer or supplier and the precautions set out in their safety data sheets and 
container labels should be followed. All preservatives should be handled with care in accordance with the 
manufacturer's specific instructions. Potential health and safety hazards include but are not limited to the 
following: 
a) inhalation, absorption through the skin or ingestion of toxic substances, including fumes, vapours and 
dusts;  
b) injury to eyes and skin;  
c) fire and explosion;  
d) noise;  
e) lack of personal hygiene. 
5.3 Order of working 
5.3.1 When buildings are painted internally and externally, the exterior work should be completed first, 
especially when it is necessary to Use rooms and windows to gain access to the external surfaces or when 
painting is carried out from the scaffolding as it is struck. However, the determining factor is often weather or 
the time of year at which work is done.  
5.3.2 Work should be carried out from the upper parts of a building or structure downwards, application of 
paint following preparation in the same order, but circumstances might require modification of this. If so, care 
should be taken to ensure that finished work is not spoiled by dust and debris arising from subsequent 
preparatory work. 
5.4 Scaffolding and equipment 
Scaffolding should be adequate in quantity and type to permit safe working and avoid delays. Hazards can be 
created by the use of unsuitable or defective scaffolding and the guidance should be followed. Equipment 
should be suitable for the type of work being undertaken and in good condition. Mechanical equipment, e.g. DRS 554: 2022 
31                ©RSB2023- All rights reserved 
 for spraying, should be of a capacity or rating appropriate to the work and should operate efficiently. 
Allowance should be made for the provision of temporary heating or drying equipment where necessary. 
5.5 Supply of materials 
5.5.1 Most conventional decorative materials are available on demand or at short notice from the 
manufacturer or distributor, but this might not apply to all quantities, colours and container sizes or to 
specialist materials. Manufacture of materials not normally held in stock can take several weeks, and orders 
should be placed well in advance to avoid delay. 
5.5.2 Usually, placing of orders for materials is the responsibility of the contractor, but early issue of painting 
schedules by specifiers reduces the risk of delay in supply that could cause work to be delayed. 
5.6 Storage of materials 
5.6.1 On large projects, facilities should be provided for the storage of materials, having regard to security, 
avoidance of hazards and maintenance of materials in good condition. 
5.6.2 Some coatings, other than water-borne types, are flammable in the liquid state; precautions to prevent 
accidental ignition should be taken and emergency fire-fighting equipment provided. If the total quantity of 
flammable paints, etc. in storage exceeds 50 l at any one time, special provisions in should be taken avoid 
accidents.  
5.6.3 Containers of highly flammable liquids (flash points below 32 °C), which include certain solvents and 
specialist coatings, usually carry a warning label but, in case of doubt, reference should be made to the 
manufacturer.  
5.6.4 To maintain coatings in good condition and to prevent rusting of containers and deterioration of dry 
materials, such as powder fillers, materials should be stored in dry conditions preferably within a temperature range 
of 5 °C to 30 °C. Attention should be paid to the storage of coatings containing volatile solvents, as temperatures 
exceeding 30 °C can create excessive pressure within containers and increases the risk of fire. Water-borne 
coatings should be protected from frost.  
5.6.5 On contracts of long duration, when successive batches are delivered at intervals, dates of receipt and 
batch numbers should be recorded and storage organized so that the materials can be issued in the same order as 
they were received. If batch numbers are missing or illegible, the containers should be marked with the date of 
receipt. 
5.7 Protection of components on site 
5.7.1 General 
Measures should be taken to prevent damage or deterioration of components and factory applied treatments 
on site, i.e. during off-loading, handling, storage and erection. If mechanical lifting equipment is used to handle 
large or heavy components, slings should be well padded at contact points. Wrapping or other means of 
protection provided by the manufacturer should not be removed before it is essential to do so. Factory coated 
articles and components should be stored away from areas subject to pedestrian or vehicle traffic and be 
protected against damage and soiling.  
©RSB 2023- All rights reserved                  32 
 5.7.2 Joinery 
5.7.2.1 Where possible, joinery, primed or unprimed, should not be kept in external storage, especially 
when it is to be installed in a centrally heated building. If external storage cannot be avoided, the components 
should be protected against moisture and other adverse climatic conditions. Components, whether stored 
indoors or outdoors, should not be in direct contact with the ground.  
5.7.2.2 If stacking is necessary, spacers should be placed between the components to permit air 
circulation and, in the case of primed joinery, to prevent sticking at contact surfaces. 
5.7.3 Metal components 
Where possible, metal components prepared and painted with part or the whole of the coating system before 
delivery to site should, size permitting, be stored indoors. If external storage cannot be avoided they should be 
protected and stacked as described in 5.7.2. 
5.7.4 Structural steel members 
5.7.4.1 Primed structural steel members, if stored externally, should be stacked in such a manner that 
they do not retain water even if no cover is provided. The bottom layer in the stack should be laid on timber 
packaging to raise it above the ground and the rainwater splash zone. Spacers should be placed between 
subsequent layers to permit air circulation and prevent sticking.  
5.7.4.2 Consideration should be given to applying additional coats, e.g. of primer, when there is a 
possibility of long delay between initial and final painting after erection. 
5.8 Off-site work 
5.8.1 Many components, such as primed and finished joinery, blast-cleaned and primed steelwork, pre- 
treated non-ferrous metal components and pruned or sealed building boards, are now factory coated off site. 
Where components are supplied partially-painted, e.g. primed, the treatment or coating should have 
properties appropriate to the exposure conditions or conditions of service. The primer (or other treatment) and 
coatings to be applied should be compatible.  
5.8.2 Measures should be taken to prevent damage to primed and finished components during transit, as it 
might not be possible to effect repairs to a standard equal to that of the original. The painting specification for 
the site work should detail responsibility for repairing any damage. The manufacturer's or supplier’s 
recommendations for repairing damage caused in transit or during installation and for subsequent 
maintenance treatment should be followed. 
5.9 Workforce and supervision 
5.9.1 The number of operatives employed should be appropriate to the size of the contract, its planned 
duration and the nature and availability of the work involved. Preparation is generally more labour intensive 
than application, and the size and deployment of the workforce should allow for this. On extensive ceiling and 
wall areas, there should be a sufficient number of operatives to ensure working wet edges are maintained 
(see 9.3.2.3) and should take into account working conditions and the characteristics of the coatings to be 
applied.  DRS 554: 2022 
33                ©RSB2023- All rights reserved 
 5.9.2 Operatives should be skilled and experienced in the types of work involved and with the materials, 
methods and equipment to be used. With novel materials, methods or equipment, special training might be 
necessary.  
5.9.3 Adequate supervision should be provided, having regard to the nature of the work and the size and 
deployment of the workforce. Supervisors should be experienced in all aspects of the work for which they are 
responsible. They should be provided with copies of all working documents, e.g. specifications, painting 
schedules and product information necessary for effective supervision and control of the work. They should 
also be provided with, or have ready access to, test equipment, e.g. moisture meters, film-thickness gauges 
and flow cups, when the nature of the work requires it. 
5.10 Inspection and supervision 
Inspection procedures should be carried out in accordance with Clause 10, which may necessitate the 
sampling and testing of materials on a regular basis (see 5.11 and 10.3). 
NOTE For large contracts, specific stages of the work might be subject to inspection and approval by a nominated person or 
specialist inspection organization to ensure compliance with the specification. Inspection does not remove or diminish the contractor's 
responsibility for proper supervision of the work. 
5.11 Materials sampling and testing 
The routine sampling and testing of materials should be carried out as described in Clause 10. 
NOTE Sampling and testing procedures can be time-consuming and expensive and are effective only if they are properly implemented. 
6 Exchange of information 
6.1 General 
6.1.1 Specifications and other documents needed in respect of initial or maintenance painting should be 
prepared in sufficient detail to afford proper guidance in the preparation of estimates and the execution of the 
work.  
6.1.2 Where relevant, there should be an exchange of information at an early stage between the painting 
contractor or subcontractor and those responsible for the constructional work, including other trades affect or 
be affected by painting.  
6.1.3 A painting project can involve several parties, including client, main contractor and subcontractors, 
suppliers and inspectors. Copies of all relevant documents should be available to all parties, including site 
personnel responsible for supervision. 
6.2 Specification 
6.2.1 General 
A specification should be clear, concise and unambiguous. The prime functions of a specification for initial or 
maintenance painting are:  
©RSB 2023- All rights reserved                  34 
 a) to describe the substrates to be treated and the means by which the required finish is to be achieved 
including surface preparation, materials, systems, application methods (where relevant) and the 
conditions under which the work is to be done;  
b) to provide a basis for accurate pricing and tendering;  
c) to serve as a comprehensive reference document for all parties;  
d) to act as a reference if disputes arise or arbitration is necessary. 
6.2.2 Surface preparation 
6.2.2.1 For initial and factory painting, many substrates will benefit from specific surface treatments and 
preparation, which should be discussed with the coating manufacturer.  
6.2.2.2 The nature and extent of preparatory work should be specified as clearly as possible because of 
its influence on costs, appearance and subsequent performance. Imprecise terms such as "thoroughly 
prepare" or "burn off where necessary", without further qualification, should be avoided (see 11.5.2.1). In 
circumstances where it is difficult to describe the standard of preparation to be achieved, for tendering 
purposes, a sample area should be prepared as an indication of the standard required.  
6.2.2.3 Where a particular method of preparation is specified, it should be appropriate and relevant to the 
result required. For example, if a requirement to "remove all rust and scale by chipping, scraping and wire 
brushing" cannot be achieved (see 8.3.4.2.4), the choice lies between selecting a more effective method or 
accepting a lower standard of preparation which will lead to a shorter life expectancy for the coating system. 
6.2.3 Coating system materials 
All the materials in a coating system should, if possible, be obtained from the same manufacturer. Where 
differing makes or brands are specified, a check should be made to ensure they are compatible (see 7.3.5). 
Materials should be used strictly in accordance with the manufacturer's instructions, including guidance on 
whether thinning is permissible (see F.3.1). For work of modest size or where relatively few finishes or colours 
are to be used, information identifying different coating systems with particular areas should be incorporated in 
the specification (see also 6.4). 
6.2.4 Application 
The specification should clearly state if circumstances require or preclude the use of particular methods of 
application and should indicate any requirements or constraints in respect of the conditions under which work 
is to be carried out or, if necessary, suspended, e.g. temperature, humidity, climatic conditions or other factors 
(see 9.1 and 11.4). 
6.2.5 Inspection procedure 
Where the work is to be subject to inspection, the intended inspection procedure should be described in the 
specification (see 5.10). DRS 554: 2022 
35                ©RSB2023- All rights reserved 
 6.3 Bills of quantities 
Bills of quantities should be prepared in accordance with a document such as Code of procedure for the 
measurement of building work ASTM E 1185-15. It is essential that the relevant edition, or any other method 
of measurement adopted, is stated. 
6.4 Schedules 
6.4.1 For large or more complex projects, the preparation of a painting schedule, detailing location, nature 
of substrate, coating system and (where relevant) colour is recommended.  
6.4.2 A painting schedule should not be regarded as a substitute for the painting specification; site 
personnel responsible for supervision should have copies of both documents. 
6.5 Drawings 
Drawings should be used for large projects either for tendering purposes or as an aid to the organization and 
control of work. 
6.6 Records 
6.6.1 Painting and decorating work is usually carried out at regular intervals as a part of an overall 
maintenance schedule and so a planned approach is essential. Planning is dependent on availability of 
information, and therefore, where expenditure on maintenance painting is significant, accurate records should 
be maintained.  
6.6.2 The essential information to be recorded includes dimensions, details of initial and maintenance 
coating systems (including preparation) and costs. Other relevant information might include the conditions 
(e.g. weather, atmosphere or exposure conditions), methods of application employed, size of labour force and 
any special difficulties or problems encountered.  
6.6.3 When work is subject to independent inspection during application, the inspection reports should be 
retained as a permanent record. Similarly, where a system of regular inspection of paintwork is in operation, 
as recommended in Clause 11, any observations should be recorded. Apart from its contribution to ease and 
economy of maintenance, a system of recording can assist in the investigation of failures and the settlement 
of disputes. 
7 Materials 
7.1 Functions of coatings 
7.1.1 General 
In situations where the requirements of coating systems are specialized, the advice of a consultant or 
experienced paint manufacturer should be sought.  
©RSB 2023- All rights reserved                  36 
 7.1.2 Protection by coating systems 
The level of protection the coating systems can offer depends upon the ability of the coating to prevent 
moisture, atmospheric pollutants, aggressive chemicals or other destructive elements coming into direct 
contact with the surface. The effectiveness of the coating depends upon its composition, especially its 
thickness, and the severity of attack. Where possible, particularly in severe conditions, consideration should 
be given to reducing dependence on the protective properties of coatings, e.g. by using less vulnerable 
building materials, by modifying the design of components or by environmental changes such as improved 
ventilation (see 4.6.2). 
7.1.3 Decoration 
7.1.3.1 Even where the main emphasis is on protection or some other function, coatings should 
contribute to the overall appearance and decorative effect of buildings; in many instances, paint is the main 
decorative medium, providing the desired colours and degree of gloss or texture.  
7.1.3.2 Paint colours and their coordination with those of other elements in the decorative scheme, such 
as furnishing fabrics, floor coverings, laminated and ceramic goods, is important and should be selected in 
accordance with the overall design specification. 
7.1.4 Hygiene 
7.1.4.1 Where specified, the coating should have the ability to withstand regular cleaning; where high 
standards of hygiene or sterile conditions have to be maintained, this might be the most important function. 
The coating should be of a type that resists not only the soiling agent but also the cleaning agent and method 
used.  
7.1.4.2 In situations favourable to the development of mould or bacterial growths, coatings having anti- 
microbial properties can be helpful, although too much reliance should not be placed on the ability of coatings 
alone to prevent mould or bacterial growth and, where possible, they should be supplemented by other 
measures as described in 4.6.4.4. 
7.1.5 Special functions 
The coatings should be selected so that they are appropriate to the conditions of their use, e.g. of resistance 
to high humidity or direct chemical attack, reduction of fire hazard including surface spread of flame and 
inhibition of mould or bacterial growth (see 4.6.4). 
7.2 General properties of coatings 
7.2.1 General 
Most of the coatings used on buildings pass from a wet stage to a dry film. Properties during the wet stage are 
described by terms such as viscosity, rheology, etc. and will have a direct influence on the application 
properties, flow and the final film thickness of the dry film. Coatings should therefore be selected according to 
the exposure conditions in which they are to be used. DRS 554: 2022 
37                ©RSB2023- All rights reserved 
 7.2.2 Viscosity 
7.2.2.1 For most coatings, viscosity is the resistance offered by the material to shearing forces, e.g. 
brushing or rolling, and, consequently, directly affects the ease with which the material can be applied. 
Indirectly, it can influence film thickness because, if the viscosity is low, the coating can be spread out too far, 
yielding an excessively thin film. If it is too high, it can be difficult to apply the coating in a film of uniform 
thickness, especially by brush.  
7.2.2.2 Application properties cannot always be assessed either from the apparent consistency of the 
material in the container or by stirring or pouring, because of the effect of thixotropic and other Theological 
effects (see 7.2.3). 
7.2.3 Flow 
Although good flow is a desirable attribute in a finish, excessive flow can make the material difficult to control 
hi application and cause running and sagging, therefore, flow properties should be determined before work 
commences. Coatings with good flow tend to recede from external angles and sharp edges, reducing the 
thickness and protective value of the film at these points. In these circumstances primers and undercoats 
should be used as they are usually formulated to flow less freely than finishes. 
NOTE The consequences of poor flow are uneven film thickness such as with thin areas (e.g. brush-marks, spray mottle) that are 
below the average film thickness. These will confer less protection to the substrate. Poor flow will also adversely affect the reflectance 
properties and in gloss paint show poor distinctness of image. 
7.2.4 Film thickness 
The method of application should be considered as it can affect film thickness (see 9.3), and the protective 
properties of a coating are generally in direct proportion to its film thickness which can also influence the filling 
and levelling properties. 
Most coatings have a build determined by the application and other characteristics. For most general purpose 
building paints, this should be in the order of 20 um to 35 um per coat dry film thickness. Some special 
purpose coatings, such as low-build wood stains or two-pack pre-treatment primers, should have dry film 
thicknesses of 10 um or less. In addition, depending on type, high-build coatings can yield films in the range 
60 um to 3 mm (e.g. textured masonry paints), although 100 um to 250 are more typical. 
NOTE 1 Film thickness is determined essentially by the proportion of non-volatile solids (e.g. pigment or resin) present in the coating 
and its flow characteristics. 
NOTE 2 Film thickness can be expressed as wet, i.e. the thickness immediately after application, or dry when the volatile 
constituents have evaporated. Dry film thickness is the significant factor in relation to protection and filling properties. 
7.3 Components of coating systems 
7.3.1 General 
A coating system comprises at least two coats either of the same material or a sequence of coats of differing 
type (e.g. primer, undercoat, finish, as described in 7.3.2 to 7.3.4). Coats should be selected according to the 
type of surface to which it will be applied and the nature and function of the coating required. Where the 
coating system provides a protective function, more than two coats might be required. Where the coating  
©RSB 2023- All rights reserved                  38 
 system consists of a sequence of coats of differing type, the compatibility of the individual coats (see 7.3.5) 
should be taken into account in the selection of coats. 
7.3.2 Primers and sealers 
An essential function of a primer is to secure good adhesion to the surface to which it is applied and, in turn, to 
provide a base to which the succeeding coats will adhere; other functions might include: 
a) the prevention of undue absorption of binder from the subsequent coats, leaving them under bound or 
lacking in gloss on absorbent surfaces, such as wood, lightweight blocks, plaster and many building 
boards;  
b) the penetration of porous substrates such as wood and masonry to improve adhesion and other 
performance factors;  
c) the inhibition of corrosion on metal, especially iron and steel;  
d) a reduction of the risk of attack on subsequent coats on surfaces of an alkaline nature, such as 
concrete, cement rendering, asbestos-cement and some types of plaster;  
e) the provision of protection in the interval between erection or fixing and application of the complete 
coating system on new wood, metal and other materials exposed to attack by moisture or other 
adverse elements. 
NOTE 1 Sealer is a term often loosely applied to coatings which might combine some of the functions of primers described in a) to d) 
with other functions, or which might be used for purposes other than priming. 
Examples include: 
1) aluminium-pigmented primers that can be used as wood primers and also as sealers for bituminous 
surfaces other than wood (see 8.15);  
2) primer-sealers for powdery or friable surfaces (see 11.5.5) or for plaster and similar surfaces of high 
or variable porosity (see 8.6.2.4); 
3) protective coatings, usually unpigmented, e.g. clear sealers for metal sprayed steel (see 8.4-1.2) and 
some multi- coloured finishes (see Table 7).  
NOTE 2 Well-thinned first coats of water-borne paint might be needed on plaster of high or variable porosity (see 8.6.2.4). These are 
sometimes referred to as sealing or mist coats. 
7.3.3 Undercoats 
The essential function of undercoats is to provide a uniformly opaque base of a colour appropriate to that of 
the finish, but they also contribute to the thickness, filling properties and cohesion of the paint system.  
Manufacturer's recommendations regarding the use of undercoats should be observed. In some 
circumstances, undercoats might not be needed, or can be replaced in part by additional coats of finish. Many 
solvent-borne matt or mid-sheen finishes, for example, can be applied direct without undercoats to primed or DRS 554: 2022 
39                ©RSB2023- All rights reserved 
 previously painted surfaces. Solvent-borne gloss finishes are usually applied over undercoats, but in three-
coat systems on primed or previously painted surfaces, with the manufacturer's approval, a system of one 
undercoat and two coats of gloss finish should be used in preference to two undercoats and one coat of finish, 
for greater durability externally or in severe internal exposure conditions. 
NOTE Some manufacturers may restrict the use of general purpose undercoats to interior use, and will have more specific 
proprietary materials for external use. 
7.3.4 Finishes 
The finish is the final coat in the system and should be selected to provide the required colour, degree of 
gloss, texture or other attributes, including resistance to weather, chemical attack and mechanical damage. In 
this respect, the finish is the most important coat in the system since its appearance and performance in 
service are frequently the criteria by which the coating system as a whole is judged. However, the finish 
should not be used to compensate for deficiencies in preceding coats in the system, whether these relate to 
quality, suitability or application. 
7.3.5 Compatibility of coatings 
7.3.5.1 It is essential that the individual coats in the system are mutually compatible. Compatibility is 
influenced mainly by the composition and physical properties of each of the coatings in the system and, to 
some degree, by their juxtaposition and age. Incompatibility can be a cause of poor adhesion between coats 
in a system. 
NOTE For example, a coating based on a solution binder (see F.2.5) might be unsuitable for use over a drying-oil/resin type 
coating, because its solvents can soften or disrupt the latter, although no problem might arise if the sequence of coats is reversed. 
Similarly, application of a hard coating over a softer one can result in cracking of the composite film while application of the softer coating 
over the harder one can be satisfactory. 
7.3.5.2 Compatibility problems are less likely to arise with systems comprising coatings of similar 
composition and properties but, even with these, slight variations in the same types of coatings from different 
manufacturers can adversely affect the performance of the system. It is advisable, therefore, to ensure that all 
the coatings in a system are from the same manufacturer and are used in accordance with the manufacturer's 
recommendations regarding the sequence and number of coats. 
7.4 Ancillary materials 
7.4.1 Cleaning agents 
Surface cleanliness is essential to the performance of coating systems. Detergent solutions or sugar soap are 
usually adequate for normally soiled surfaces. All residues should be completely removed prior to applying the 
coating system. For removal of oil or grease, proprietary solvent-emulsion cleaners should be used (see 
11.5.3). 
7.4.2 Sterilizing washes 
Surfaces contaminated with mould or algal growths should be treated before coatings are applied. Household 
bleach solutions are often effective in killing the growths but, in severe cases, proprietary mould-inhibitive 
washes provide a measure of protection against their reappearance (see 11.5.8). All residues, including 
chemicals and dead mould/algal spores should be completely removed prior to applying the coating system.  
©RSB 2023- All rights reserved                  40 
 7.4.3 Knotting 
7.4.3.1 Sealers should be used to hold back resin, tannin and other stains, which could discolour wood 
coatings on some wood species (see 8.1.1). The problem is most acute with white water-borne finishes. 
NOTE The most common problems are associated with knots in the wood. Traditional sealers based on shellac solutions are 
known as knotting. 
7.4.3.2 Where knotting is used to retard discoloration of light-coloured opaque finishes, a quick-drying 
solution e.g. of shellac in industrial methylated spirit should be applied to knots or resinous areas in wood 
before priming. Two coats are more effective than one, however, knotting is not likely to be completely 
effective in cases of resin exudation. 
7.4.4 Stoppers and fillers 
7.4.4.1 General 
The distinction between stoppers and fillers has become less clear-cut with the widespread use of proprietary 
materials, many of which, although described as fillers, are used for both purposes. More meaningfully, the 
materials might be categorized as stoppers, general purpose stoppers/fillers and surface fillers. Methods of 
stopping and filling are described in 9.2.4. 
7.4.4.2 General purpose stoppers/fillers 
7.4.4.2.1 General purpose stoppers/fillers are usually water-mixed and comprise the following. 
a) Powder fillers . These are supplied in powder form for mixing with water and are usually based on 
water-soluble cellulose and gypsum or white Portland cement. Those containing gypsum are suitable 
for general use as stoppers and fillers in dry interior situations.  
b) Water-borne fillers . These are usually based on vinyl or acrylic resin dispersions and are supplied in 
paste form, ready for use. Materials of this type vary considerably in characteristics and usage. 
7.4.4.2.2 Powder fillers are not usually suitable for use for external work, especially on wood, but the 
manufacturer's recommendations in this respect should be observed. Portland cement types are suitable for 
external use on masonry surfaces and should not be used on woodwork. 
7.4.4.2.3 Where water-borne fillers are used the manufacturer's recommendations, especially regarding 
suitability for exterior use, should be observed. It should be noted that some exterior grades contain coarse 
particles, making the attainment of a fine finish difficult. Linseed oil putty should not be used as a stopper. 
7.4.4.2.4 For stopping deep holes in woodwork, proprietary materials based on two-pack polyester or 
epoxy resins can give good performance but it is essential to use a grade supplied specifically for use on 
wood. 
7.4.4.3 Surface fillers 
Surface fillers formulated specifically for use on timber are preferred to the general purpose types when a high 
standard of finish is required, especially with solvent-borne paint systems. They are supplied ready for use as DRS 554: 2022 
41                ©RSB2023- All rights reserved 
 smooth, finely ground, creamy pastes, and should be applied with a wide filling knife or spatula. The types in 
general use are water-borne, but solvent-borne formulations are also available. 
7.4.5 Mastics and sealants 
Mastics and sealants are mainly used for the repair or replacement of external pointing between window or 
doorframes and adjacent masonry. They do not need to be over-painted, except for one- pack, non-elastic 
types, which should be over-painted. Silicone mastics and sealants should not be over-painted. 
7.4.6 Water repellents 
Water repellent solutions should be used when rain penetration of walls has caused internal dampness. 
8 Substrates and coating systems 
NOTE 1 Although concerned essentially with new work, surfaces that might not have been painted initially, such as external masonry 
or non-ferrous metal, come within the scope of this clause. Maintenance treatment is described in Clause 11, but much of the information 
given here is relevant. 
NOTE 2 The coatings referred to in this clause are generally those of conventional type, as defined in A.2 and described in Tables 12 
to 18, but 4.6.4 describes some functions and situations for which specialist coatings (see A.3 and Table 10) or modified conventional 
coatings might be necessary. 
8.1 Wood 
8.1.1 Extractive 
8.1.1.1 General 
8.1.1.1.1 The potential for extractives to cause problems should be taken into account during the 
preparation of wood for coating. Wood material contains typically 5% to 20% of soluble material (see F.2.5). 
Extractives confer desirable properties such as durability and colour to wood, but they may also disrupt or 
discolour surface coatings.  
8.1.1.1.2 Extractives are manifested both as resins and in the form of soluble staining chemicals such as 
tannin. Knots often contain a disproportional high percentage of resin and extractives, which can cause 
localized discoloration and physical disruption of paint. These problems should be alleviated through the 
application of a knot treatment or use of a purpose-designed stain-blocking primer (see also 7.4.3 and C.2.8). 
8.1.1.2 Resinous and oily materials 
8.1.1.2.1 Some hardwoods (e.g. gurjun, keruing and agba), and occasionally resinous pines (see C.2.5) 
contain a high content of resin distributed through the wood, which can give rise to severe exudation 
problems. Kiln drying reduces the activity of resin in potentially troublesome timber but when resin content is 
very high, exudation can continue for long periods, especially on external woodwork exposed to the sun. In 
such situations, dark coloured paints should be avoided.   
©RSB 2023- All rights reserved                  42 
 8.1.1.2.2 Other woods, such as teak and some cedars, contain oil, which can impair the drying, hardening 
or adhesion of coatings. These woods should be washed down with methylated spirits immediately before 
priming or varnishing. However, they can usually be painted satisfactorily if an aluminium primer (3/5) is used. 
8.1.1.3 Tannin and other extractives 
8.1.1.3.1 Some species, notably Western red cedar and sequioa among the softwoods, and among 
hardwoods oak and chestnut, contain a relatively high level of tannins distributed throughout the wood. When 
finishing using a water-borne paint, a primer possessing stain-blocking properties should be used.  
8.1.1.3.2 Wood species containing high levels of tannins react with iron to produce strong blue-black 
discoloration. Contact with steel tools should be minimized, non-ferrous fixings should be used, and under no 
circumstances should smoothing be carried out using steel wool. 
8.1.2 Moisture content 
Wood should be painted or varnished when its moisture content is near to that at which it will stabilize in 
service, generally 15 % to 19 %, but lower in buildings which are heated continuously, typically 9 % to 11 %. 
NOTE Excessively dry timber swells as it takes up moisture (see C.2.3), imposing stresses on the coating; damp timber shrinks 
during drying, causing joints to open, creating further points for water to enter. Also, blistering or flaking of the surface coating is likely to 
occur on damp timber. 
8.1.3 Penetration of binder 
8.1.3.1 Deep penetration is not necessary for priming coats to adhere and can be both wasteful of 
material and detrimental to performance as binder can be preferentially absorbed, leaving the dried film under 
bound or weakened.  
8.1.3.2 The large pores in hardwoods could be bridged by paint coatings, leaving an air space beneath 
the film and forming a weak point that can initiate breakdown. To prevent this, filling should be undertaken 
when hardwoods are painted.  
8.1.3.3 Ease of penetration of liquid (see C.2.4) should be taken into account before using preservative 
treatment 
8.1.4 External influences 
8.1.4.1 Moisture 
8.1.4.1.1 The water-excluding efficiency of a wood coating is an important property that determines the 
extent of dimensional movement of coated wood in service, as well as influencing the risk of fungal decay. It 
should therefore be taken into account when selecting or specifying wood-coatings.  
8.1.4.1.2 Multi-coat, high-build coating systems are reasonably effective barriers to the free movement of 
liquid moisture and vapour provided the coating is continuous and remains intact. However, all coatings allow 
some passage of water during wetting and drying, and this leads to consequent movement of the wood. 
Coatings should be selected that relate to the expected end-use category. Thus highly permeably wood stains 
are suitable for fencing where free movement is acceptable. A less permeable coating is required for window DRS 554: 2022 
43                ©RSB2023- All rights reserved 
 joinery where movement should be controlled. For cladding an intermediate level of permeability is 
acceptable.  
8.1.4.1.3 Moisture could gain entry through open joints, defective putties and sealants, and the paint film 
might then hold the water in. In jointed components the principal route for moisture entry is through end grain 
concealed within the joints. Components that have their end grains sealed during manufacture should be 
selected where the reduction of wetting and the improvement in coating performance is desirable.  
8.1.4.1.4 Moisture movement places a cyclic strain on the coating system that may eventually result in 
cracking. Some coating formulations offer higher film flexibility and should be used where good exterior 
durability is necessary. The use of such coating in no way reduces the need for good design and an 
appropriate preservative treatment should still be used. 
8.1.4.2 Weathering 
NOTE On external exposure to sun and rain, unprotected wood loses its original colour and the surface degrades until it consists of 
a thin layer of loosely matted fibres, usually dirt-stained and darkened by fungal blue stain and iron staining. After periodic wetting and 
drying, the growth rings can become prominent and splitting and distortion can occur. 
8.1.4.2.1 If it is desired to preserve the natural appearance of external woodwork, protective surface 
treatment is essential (see Table 9). Denatured wood should be removed back to a sound wood surface 
before application of a coating as weather-degraded wood is a very poor substrate. Even when wood is not 
obviously degraded, the paint holding properties could be severely compromised. Wood should therefore be 
protected from the elements, and for exterior exposure, will benefit from a penetrating treatment as the first 
coat of any coating system.  
8.1.4.2.2 Solar heat gain causes shrinkage of wood and consequent cracking and opening of joints; it can 
also increase resin exudation, resulting in discoloration and disruption of coatings. Dark finishes should be 
avoided as they exacerbate this. 
8.1.4.3 Fungal attack 
NOTE Wood, which is not naturally resistant, is susceptible to fungal attack if its moisture content exceeds a mass fraction of about 
22 % for lengthy periods. In painted woodwork, the principal agents of decay are the wet-rot fungi. Surface moulds and blue-stain fungi 
have little effect on the durability of timber although they are unsightly and can disfigure paintwork. Exterior timbers not in contact with the 
ground are unlikely to rot if they are of moderately durable species or better, but this classification applies only to the heartwood; all 
sapwood is vulnerable to decay. 
Where timbers of a lower durability rating are used, or if appreciable quantities of sapwood are present, 
application of a preservative, where practicable by impregnation, should be undertaken to prevent fungal 
attack. 
8.1.5 Preservative treatments 
Provided adequate drying of the treated wood is allowed prior to painting, preservation will not give rise to any 
adverse effects on paint performance. Preservative treatment of timber according to species, end use and 
desired service life should be in accordance with ISO 15206. The treatment of components, e.g. window 
joinery, which are to be subsequently coated should be as follows. 
a) Treatments for window joinery and other external building timbers not in ground contact:  
©RSB 2023- All rights reserved                  44 
 1) Copper-based preservative formulations which are chromium and arsenic free can be used, but the 
long term performance of these formulations is not fully established by field trials. 
2) Organic solvent and micro-emulsion preservatives, e.g. conforming to ISO 21887&ISO 15206 and 
water- repellent types, containing waxes or resins, suitable for painting, can be used. These types of 
preservatives can be applied by immersion or the double vacuum process as specified in ISO 15206. 
Application by brushing or spraying is not recommended except for site treatment of cut ends etc., or 
in remedial work. These preservatives are generally suitable for over- painting provided a minimum 
of 48 h in conditions of good ventilation is allowed for evaporation of solvent, but users should satisfy 
themselves as to the compatibility of the particular treatment with the coating system to be applied. 
3) Diffusion treatment with disodium octoborate. This treatment can be carried out on freshly felled 
timber and can be applied to seasoned timber. The salts remain water-soluble and can affect 
coatings if the timber becomes wet although, in practice, few difficulties appear to arise. 
b) Treatments for fencing and gates in or out of ground contact: 
Application of preservatives by brush is a less effective means of conferring resistance to biological attack 
than impregnation, because penetration of the fluid is limited and the protective zone relatively shallow. 
Nevertheless brush application should be used for treatment of component repairs prior to painting, and also 
in conferring resistance to blue stain disfigurement of paints and stains. Clear preservative primers are 
available, usually of solvent-borne type, which contain resin in addition to fungicide and serve to stabilize the 
wood surface and improve the performance of the coating system. They should be applied liberally, 
particularly over end-grain surfaces.  
Preservatives are also a useful adjunct in prior-to-painting repairs on external timber components. After 
remedy of defective timber using resin repair or traditional methods of timber inserts, wood which is sound but 
deemed to be vulnerable to decay should be protected by the insertion of preservative plugs to provide a 
latent reserve of fungicide. 
8.1.6 Surface preparation, priming, stopping and filling 
8.1.6.1 General 
8.1.6.1.1 The moisture content of the timber should be measured before painting and should not exceed 
the expected equilibrium value (see 8.1.2). An electrical moisture meter with long probes should be used so 
that readings can be taken at a depth not so readily affected by surface drying. 
NOTE Moisture content can be measured with sufficient accuracy for painting purposes with an electrical moisture meter of the 
conductive type. Electrical moisture meters can give a falsely high reading if soluble salts are present, e.g. from preservative treatment 
with disodium octoborate. 
8.1.6.1.2 If there is a delay between delivery to site and fixing or erecting of joinery, it should be protected 
against ingress of moisture (see 5.7).  
8.1.6.1.3 If limber has received preservative treatment, time should be allowed for drying out or evaporation 
of solvent before priming (see 8.1.4). DRS 554: 2022 
45                ©RSB2023- All rights reserved 
 8.1.6.2 Surface preparation 
8.1.6.2.1 General 
Preparatory treatment of wood should be undertaken before priming, e.g. cleaning, abrasion and treatment of 
knots. Thorough surface preparation is especially important on wood that has been exposed to weather 
without protection. 
8.1.6.2.2 Cleaning 
A clean surface is essential to the satisfactory adhesion and appearance of the paint system. Dirt and surface 
deposits, exuded resin and soluble salts arising from preservative treatment should be removed. If the surface 
is contaminated with oil or grease, solvent cleaning may be necessary (see 7.4.1). 
8.1.6.2.3 Abrasion 
Where necessary, abrasion should be used to clean the surface, reduce roughness and improve paint 
adhesion.  
Wood can be sanded mechanically or manually using traditional glass paper or one of the more modern 
abrasive pads with incorporated grits. It is essential to use a grade of abrasive paper appropriate to the 
surface; excessively coarse grades can damage the wood fibres, impairing the appearance and possibly the 
performance of the paint system. The surface should be sanded in the direction of, and not across, the grain 
without using excessive pressure, which can damage the wood fibres. Care should be taken not to damage 
moulding and arris edges.  
Steel wool should not be used on unpainted joinery as it may leave tiny particles of wire which can rust and 
spoil the finish.  
Surface preparation is particularly important for weather-degraded wood, and is best achieved by planing or 
mechanical sanding. An effective alternative is scraping the wetted denatured surface, followed when dry by 
thorough abrasion, and the application of a transparent preservative primer (e.g. 3/6). 
8.1.6.2.4 Knot treatment 
Discoloration of paint, especially noticeable with light colours, can occur over knots and resinous areas 
especially if the wood has been treated with preservative containing certain organic solvents (see 8.1.5 and 
C.2.7). Discoloration may be minimized by the application of a knot treatment, e.g. knotting (see 7.4.3).  
Heavy applications and the use of knotting which has thickened through evaporation of solvent should be 
avoided; otherwise paint adhesion can be impaired. Knotting should not be used if finishing with semi-
transparent wood stains.  
In severe instances of resin exudation from knots, the knot may be removed by drilling, followed by filling of 
the hole.  
©RSB 2023- All rights reserved                  46 
 8.1.6.3 Priming 
NOTE Primers for wood are listed and described in Table 3, and typical applications are indicated in Table 12 and Table 13. 
8.1.6.3.1 A good primer, applied to dry sound substrates, is the foundation of a durable paint system. Using 
components primed in the factory or works is recommended but if site priming is necessary, it should be 
carried out immediately after delivery of the joinery, provided that its moisture content is at an appropriate 
level (see 8.1.2). Although single coats of primer retard surface degradation by sunlight (see 8.1.4.2), they 
provide only limited protection against moisture, (especially if the wood has not been treated with a water-
repellent preservative) and therefore the full system should be applied as soon as possible. Primed joinery, if 
not fixed or erected immediately, should be properly stored (see 5.7).  
8.1.6.3.2 If pruned woodwork has been exposed for a lengthy period, the condition of the primer should be 
checked before continuing application of the paint system. It is important that areas of defective or poorly 
adhering primer be removed and the exposed areas reprimed. If the primer is firmly adhering but is chalking or 
powdery, it should be lightly abraded and a further coat applied. 
8.1.6.4 Stopping and filling 
NOTE Materials used for stopping and filling are described in 7.4.4 and the techniques are described in 9.2.4. 
Drying-oil/resin stoppers and fillers should be used only on primed surfaces; otherwise oil is absorbed leaving 
the material under bound. 
8.1.7 Coating systems for interior use 
NOTE For information on coating systems for interior wood, see Table 8 and Table 12. 
8.1.7.1 Solvent-borne paints 
8.1.7.1.1 Internal use of solvent-borne paints should be restricted because of increasing environmental and 
legislative pressures aimed at eliminating health risks to painters and reducing volatile organic compounds 
(VOCs). 
NOTE The traditional solvent-borne system consists of three-coat application: primer, undercoat and gloss finish. However, mid-
sheen and matt finish solvent-borne paints are sometimes applied coat-on-coat, or as two coats over the primed wood. 
8.1.7.1.2 If it is necessary to capitalize on the speed of drying of the water-borne systems, water-borne 
primers and primer/undercoats should be employed under the final gloss finish. 
8.1.7.2 Water-borne paints 
Water-borne paints should be applied using synthetic filament rather than natural bristle brushes as the 
synthetic filament aids the flow of the coating material and reduces brush-marking. Before the application of 
water-borne paints, bare wood knots should be sealed to reduce the risk of tannin staining (see 8.1.1.1). 
8.1.8 Coating systems for exterior use 
NOTE For information on coating systems for exterior wood, see Table 9 and Table 13. DRS 554: 2022 
47                ©RSB2023- All rights reserved 
 8.1.8.1 General 
Coating systems for exterior use should provide a flexible weather-resistant coating that maintains its integrity 
and protective effectiveness in the long term. 
8.1.8.2 Paint systems 
8.1.8.2.1 Solvent-borne exterior paints 
Solvent-borne exterior paints should be used when a high quality appearance and a more tolerant application 
under adverse weather conditions is necessary. 
NOTE Solvent-borne exterior paints are generally based on flexible alkyd resins and are available in a range of sheen levels. They 
generally adopt the traditional system approach of primer, undercoat and gloss, though in some low-sheen materials one product is 
applied in two coats over a primer, or even as three coats on bare wood. Solvent-borne exterior alkyd paints possess superior durability to 
general-purpose alkyds, but nevertheless lose flexibility during weathering. Solvent-borne exterior paints can be used over water-borne 
primers (see BS 7956). 
8.1.8.2.2 Water-borne paints 
Water-borne paints can be formulated to give high performance coatings for exterior wood and should be 
applied at a spreading rate in accordance with the manufacturer's recommendations to provide appropriate 
film thickness and so ensure long-term durability. Water-borne paints offer less resistance to being over-
brushed and minimum film thicknesses should be specified. 
NOTE 1 Water-borne paints possess a range of application benefits associated with the use of water as solvent-carrier, for example 
low-odour, low-VOC content, ease of clean-up and non-flammability. 
NOTE 2 Initial gloss and flow properties of water-borne paints are presently inferior to those of solvent-borne alkyds. Cold, damp 
exterior conditions can affect the application of these products. 
8.1.8.3 Solvent-borne and water-borne exterior wood stains 
8.1.8.3.1 Clear varnishes (9/1, 9/2) perform very poorly on exterior wood in exposed situations and should 
not be used unless frequent maintenance is acceptable. Exterior high-build wood stains should be used on 
exterior wood as they contain resinous binders to resist moisture movement, pigments and ultraviolet 
absorbers to protect against degradation by sunlight, and often biocides to protect against fungal 
discoloration. 
NOTE Modern exterior wood stains can be of solvent-borne or water-borne type, and are carefully formulated compositions 
designed to provide comprehensive protection to the wood under demanding conditions. 
8.1.8.3.2 Low-build exterior wood stains should not be used for components such as exterior joinery where 
dimensional control is important (see 8.1.4). 
8.1.8.3.3 Low-build stains should be used on components for which dimensional movement is to be 
expected, such as cladding, bargeboards, gates, fences, etc., and which often have a sawn finish.  
©RSB 2023- All rights reserved                  48 
 NOTE The moisture permeability of the wood stain is unlikely to give rise to problems, though cladding which has been poorly fixed 
(without a movement allowance) or installed at an inappropriate moisture content can distort. 
8.1.8.3.4 It is essential that maintenance of medium-build wood stains be carried out before any loss of film 
integrity, because any exposure of the wood to weathering can result in discoloration, which no semi- 
transparent coating can disguise. 
8.1.9 Flame-retardant treatments 
8.1.9.1 General 
8.1.9.1.1 Materials, either surface or impregnation treated, should be kiln dried to a maximum moisture 
content of 12% before application of a decorative coating system. It is important that the surface of the treated 
material is clean and dust free. Chemical or other surface deposits should be removed by light sanding.  
8.1.9.1.2 Treated materials can be painted with clear, pigmented and opaque products, using conventional 
methods of application, but the manufacturer's recommendations should be observed. It is essential to 
establish that any coatings do not adversely affect the spread of flame characteristics or the treated materials.  
8.1.9.1.3 Highly flammable coatings such as nitro-cellulose-based lacquers that can contribute to the risk of 
flame spread, should not be used.  
8.1.9.1.4 Care should be taken when applying a decorative coating to flame-retarded substrates that the 
flame- retardant properties are not degraded. Advice on painting over flame-retardant treated materials should 
be sought from the manufacturer. 
8.1.9.2 Inorganic flame retardants 
8.1.9.2.1 Inorganic flame-retardant treated materials should be protected at all tunes from the elements, 
both at the treatment plant and on site. 
8.1.9.2.2 The flame-retardant treated material should receive at least the first coat of the coating system as 
soon as possible and before installation.  
8.1.9.2.3 Providing these recommendations are followed, the presence of the flame-retardant chemicals in 
the wood should not affect the performance of the paint film hi dry exposure conditions. 
8.1.9.3 Resin-based flame retardants 
Resin-based flame retardants should be kiln dried after treatment, to cure the chemical within the timber.  
NOTE Resin-based flame retardants can be used externally or can be subjected to high humidity and under these conditions there 
is no loss of flame retardance or paint film integrity. 
8.2 Wood-based panels products 
MOTE For further information on wood-based panels, see Annex C. DRS 554: 2022 
49                ©RSB2023- All rights reserved 
 8.2.1 Characteristics 
8.2.1.1 Plywood 
8.2.1.1.1 Plywood for external use is manufactured with weatherproof adhesive but not necessarily with 
durable species of timber throughout; if non-durable species are incorporated, preservative treatment should 
be applied (see 8.1.5).  
8.2.1.1.2 The outer layers of plywood exposed to weather are prone to develop checking (fine surface 
cracks, defined in BS 2015) running parallel to the grain, even when painted. Plywood is available with a 
resin-impregnated paper overlay, which prevents checking and provides a satisfactory base for painting; the 
use of this type of material is recommended for external plywood cladding and similar applications when a 
paint finish is required, especially with species prone to severe checking. Exterior wood stains (see 8.1.8.3), 
especially those of the low-solids type, are less likely to give trouble and are more suitable than paint or 
varnish for use externally on plywood without a paper overlay. However, because of the low resistance of low-
solids wood stains to water vapour, fluctuations in moisture content can result in water-soluble salts, present 
in the adhesive, being brought to the surface. These are normally removed by rain but, if the surface is 
sheltered from direct rainfall, a white deposit can build up and mar the appearance. The salts should be 
washed off but will reappear until they are depleted. 
8.2.1.2 Fibre building board, wood chipboard and plasterboard 
8.2.1.2.1 When it is necessary to paint fibre building board, wood chipboard and plasterboard the 
manufacturer's recommendations should be followed in respect of board types and design details.  
8.2.1.2.2 Where a reduction in the number of site applied coats is necessary or a higher standard of finish 
is desired, fibre building boards and wood chipboards supplied with a factory-applied primer, sealer or 
surfacer on one or both faces should be selected. 
NOTE C.3.1.2 describes the four main types and the typical treatment of fibre building board. 
8.2.1.3 Wood chipboard 
8.2.1.3.1 Like timber, chipboard can be attacked by wet-rot fungus if its moisture content is above the 
critical level for lengthy periods; the physical properties of the board can also be affected. Moisture-resistant 
grades are available for use in highly humid conditions and should be installed in accordance with 
manufacturer's recommendations regarding design detailing and fixing methods. 
NOTE Preservative treatment, as recommended for wood in 8.1.5, is not usually suitable for wood chipboard. 
8.2.1.3.2 The natural surface of chipboard varies according to the method of spreading the chips during 
manufacture. If the surface has a coarse or open texture, it should be filled before painting to obtain a 
satisfactory finish. Some methods produce a surface of finer texture requiring little or no filling before painting.  
©RSB 2023- All rights reserved                  50 
 8.2.2 Preparation and coating systems 
8.2.2.1 Surface preparation 
8.2.2.1.1 Knots are rarely a problem on good-quality plywood, but any present should be treated with 
knotting before painting (see 8.1.6.2.4).  
8.2.2.1.2 Except with the more open-surface grades of wood chipboard (see 8.2.1.3), building boards do 
not usually need sanding before being painted. If sanding is considered necessary to improve adhesion to 
glossy-surfaced hardboards, a fine grade of abrasive paper should be used and care should be taken to avoid 
scoring the surface, as this can result in localized swelling along the score marks when paint is applied.  
8.2.2.1.3 Wood-wool surfaces should be cleaned with a stiff, but not wire, brush. Loose dust should be 
removed with a soft fibre brush or vacuum cleaner (the dust can be strongly alkaline). 
8.2.2.2 Stopping and filling 
8.2.2.2.1 If checking has occurred on external plywood and it is to be painted, it should be filled after 
pruning. For stopping-up nail and screw holes and repairing minor damage to the surface, either water-mixed 
or drying-oil/resin stoppers or fillers should be used.  
8.2.2.2.2 Water-mixed stoppers and fillers can be used on either primed or unprimed surfaces. On 
unprimed surfaces and on factory-pruned or sealed boards, exposed heads of nails and screws, unless they 
are rust-resistant, should be touched-in with quick-drying solvent-borne primer to prevent rust-staining. If a 
water-mixed material is used for stopping-up after priming or on factory-pruned or sealed boards, it might be 
necessary to touch-in the stopping with primer to ensure a surface of uniform absorption. Drying-oil/resin 
stoppers and fillers should be used only on primed or sealed surfaces.  
8.2.2.2.3 If a high standard of finish is desired on some types of wood chipboard, water-mixed or drying- 
oil/resin fillers can be used, but the surface should first be primed.  
NOTE Direct application of water-mixed fillers causes swelling of the wood chips; with drying-oil/resin fillers, the binder is absorbed. 
8.2.2.3 Priming 
NOTE Primers for painting plywood are as described for wood in Table 3. Table 1 gives general guidance on the selection of 
primers. 
8.2.2.3.1 Varnish and wood stains are usually applied direct, but thinning of first coats might be necessary 
and the manufacturer's recommendations should be followed.  
8.2.2.3.2 If not primed or sealed during manufacture, building boards should be primed before application 
of solvent-borne (e.g. alkyd) paint systems. Normal practice is to use primers of the types employed for wood 
or plaster (Table 3 and Table 5), but any specific recommendations of board or paint manufacturers should be 
followed.  
8.2.2.3.3 Except as indicated in Table 18, priming is not usually needed when water-borne coatings are to 
be applied to building boards. Priming of boards that have received flame-retardant treatment [see C.3.1.2, 4)] 
is recommended to prevent efflorescence or discoloration caused by reaction between water-borne coatings DRS 554: 2022 
51                ©RSB2023- All rights reserved 
 and chemicals used in the treatment. Similarly, priming of single layer wood chipboard might be necessary to 
prevent absorption of water and consequent swellings of the chips that produce a rough surface.  
8.2.2.3.4 Bitumen-impregnated insulating boards, if they are to be painted with solvent-borne paints, should 
be primed with an aluminium primer or sealer to prevent discoloration (bleeding). 
8.2.2.3.5 Traditional practice, especially with fibre building boards, is to prime or paint (back-prime) 
unexposed faces of boards to prevent absorption of moisture. In most circumstances, and provided that 
boards of appropriate types are installed in accordance with the manufacturer's recommendations, this is not 
necessary. Unless the board manufacturer advises otherwise, wood-based panel products should not be 
back-primed. 
8.2.2.4 Finishing of internal work 
The types of coating systems indicated in 8.5.2 and 8.5.3 as suitable for use on plaster, should also be used 
on building boards. 
8.2.2.5 Finishing of external work 
NOTE 1 Coatings suitable for use on plywood are shown in Table 5 and Table 7. 
8.2.2.5.1 When installed in accordance with the supplier's recommendations, some types of hardboard and 
medium board are suitable for external use.  
8.2.2.5.2 Factory-applied treatments suitable for exterior exposure are available but, when site painting is 
necessary, the types of coating systems (except cement paints) described in 8.5.3 as suitable for external 
surfaces should be used.  
NOTE 2 Typical coating systems for externally sited boards are indicated in Table 13.  
8.2.2.5.3 On external cladding, it is recommended that vapour-permeable coatings should be used; 
textured coatings are particularly suitable. Selection of systems and their performance in service is, however, 
influenced by the materials and forms of construction, and reference should be made to board and paint 
manufacturer's recommendations in specific circumstances. 
8.3 Iron and steel 
8.3.1 General 
The painting of the ferrous metal surfaces normally encountered in buildings, in moderate external and 
internal exposure conditions (see Table 2) may be undertaken using paints of conventional type. For a more 
comprehensive treatment of iron and steel, especially in situations where the exposure conditions are 
classified as severe, the areas are extensive or long-life painting systems are required, the painting should be 
in accordance with ISO 12944 for steel structures (and ISO 14713-1ISO 14713-1 for iron structures). 
NOTE 1 Non-ferrous metals, notably zinc and aluminium, are frequently used as protective coatings on iron and steel, either alone or 
in conjunction with paints. Painting systems for metallic coatings are described in 8.4. 
NOTE 2 For further information on iron and steel, see Annex H.  
©RSB 2023- All rights reserved                  52 
 8.3.2 Characteristics 
8.3.2.1 Mild steel 
Hot-rolled mild steel bears a layer of millscale. Shedding of this millscale occurs before the steel has been 
painted, giving differences in electrical potential between the exposed surface and the surrounding adherent 
scale, corrosion cells can be created and result in severe attack on the bare steel. If the scale becomes 
detached after painting is completed, costly preparation and repainting is necessary. Millscale should be 
removed as described in 8.3.4 before the steel is painted; it is essential that this be done if high-durability or 
specialist coatings are to be applied. 
8.3.2.2 Stainless steel 
If painting of stainless steel is necessary, surfaces should be abraded and degreased before application of a 
pre-treatment primer. 
NOTE Proprietary systems are available for application to stainless steel (see Table 15) 
8.3.3 Design considerations 
8.3.3.1 The effectiveness of paints in protecting iron and steel can be increased, and the risks of 
corrosion diminished, by good design.  
8.3.3.2 ISO 12944-3 and ISO 14713-1ISO 14713-1 give detailed guidance on designing for the 
prevention of corrosion, but the following aspects should be applied. 
a) All surfaces of exposed metal that need regular maintenance painting should be fully accessible. Surfaces 
such as back-to-back angle-iron trusses should be spaced far enough apart to permit painting or be 
treated with mastic or anti-corrosive paste before being butted together. Sealing gaps with gun, trowel or 
pouring grade sealants is an accepted method of protecting surfaces inaccessible for painting. Pipework, 
especially when sited externally, should be spaced from walls far enough to admit a paintbrush or paint 
glove. 
b) Drainage of trough sections should be arranged, e.g. by drilling holes, to prevent retention of water. This 
is especially important in salt-laden atmospheres. Water traps should be avoided where steel stanchions 
enter the ground or are embedded in a concrete base. Measures should be taken to prevent discharge of 
waste steam and liquids on to steelwork. 
c) Sharp, internal angles, crevices and cavities should be avoided or, if unavoidable, should be filled with 
weld metal or mastic. 
d) Electrochemical corrosion can occur at contact surfaces between dissimilar metals in the presence of an 
electrolyte, e.g. rainwater. If possible, direct contact should be prevented by measures such as placing 
plastic sheets between the contact surfaces or applying thick bituminous coatings to them. Alternatively, 
electrolyte should be excluded by making joints watertight and applying an impermeable coating. 
NOTE Rainwater run-off copper to steel could also cause corrosion. DRS 554: 2022 
53                ©RSB2023- All rights reserved 
 8.3.4 Surface preparation and priming 
8.3.4.1 General 
8.3.4.1.1 The effectiveness with which millscale and rust are removed depends upon the method 
employed; the methods in general use are described in 8.3.4.2.1 to 8.3.4.2.5. Removal of oil, grease and dirt 
is also important. If iron and steel have been exposed to severe or very severe exposure conditions, e.g. 
marine and industrial, where residual surface contaminants can stimulate corrosion, care should be taken in 
cleaning. 
8.3.4.1.2 The effectiveness of coating systems in protecting iron and steel is dependent upon the following 
factors. 
a) The nature and thoroughness of the preparatory method. The millscale and rust should be thoroughly 
removed to allow for an effective paint system to be applied. Preparatory methods are described in 
8.3.4.2. 
b) The type of primer used. Generally, primers for iron and steel should contain corrosion-inhibitive pigments 
(see F.4.5). The choice of primer is influenced by the preparatory method employed (see 8.3.4.2). 
c) The extent to which the system is able to exclude air and moisture. This is determined mainly by the total 
thickness of the paint film, its physical properties and the conditions of exposure (see Table 2). The 
minimum film thickness for satisfactory protection in moderate external exposure conditions is 
approximately 125 um but films of 250 um or more might be required in severe exposure conditions. 
8.3.4.1.3 Whenever possible, steelwork should be prepared and primed off-site; this usually compares 
favourably in cost and effectiveness with site treatment. When practicable, it is advantageous to apply off-site 
one or more of the subsequent coats in the coating system, although this might result in divided responsibility 
for the work. 
8.3.4.2 Surface preparation 
8.3.4.2.1 Abrasive blasting 
NOTE This involves directing a stream of metal shot, grit or other abrasive particles at high velocity against the surface of the steel. 
The abrasive particles are propelled by compressed air or high-pressure water (or a combination of the two) or thrown by centrifugal force 
from an impeller wheel. For some purposes, high-pressure water without abrasive particles can be used. 
8.3.4.2.1.1 Abrasive blasting is the most effective method of preparing steelwork for painting and is 
essential when specialist coatings are to be used, e.g. in severe and moderate exposure conditions. In 
respect of cost and effectiveness, blast-cleaning should be carried out under factory conditions although the 
method is also suitable for the preparation of erected steelwork in some circumstances.  
8.3.4.2.1.2 In addition to its effectiveness in removing rust and millscale, abrasive blasting provides a 
roughened surface which improves paint adhesion. Excessive roughening, however, including the use of 
abrasive particles which are too coarse for the intended thickness of paint to be applied, can produce peaks 
which protrude through the paint film and form focal points for corrosion.  
8.3.4.2.1.3 Abrasive blasted surfaces are extremely vulnerable to corrosion (flash rusting) and should be 
primed as soon as possible and in any case within 4 h of cleaning, (see 8.3.4.3). 
8.3.4.2.2 Acid-pickling  
©RSB 2023- All rights reserved                  54 
 8.3.4.2.2.1 Acid-pickling is a factory process involving immersion of iron and steel in hot acid solutions to 
remove millscale and rust but might not provide a satisfactory base for some specialist coatings and therefore 
the coating manufacturer should be referred to for advice.  
8.3.4.2.2.2 For site treatment of steelwork, proprietary washes and pastes, usually based on phosphoric 
acid should be used. They do not remove heavy rust or tightly adhering scale but can assist manual cleaning. 
Many types require washing-off; if this is not done properly, the performance of the paint can be affected and, 
if drying is slow, the steel will rust again. Washing-off water should not be allowed to run over adjacent 
brickwork or stonework. Where solutions claim to not require washing-off, the manufacturer's 
recommendations should be followed. 
8.3.4.2.3 Flame-cleaning 
Flame cleaning is not recommended and is more suitable for use in maintenance painting than in the initial 
treatment of new steel. It does not remove all rust and scale and should in no way substitute for abrasive 
blasting. It should not be used on thin sheets or on sections less than about 0.5 mm in thickness because of 
the risk of distortion, or on steel which has been coated with non-ferrous metals such as zinc and cadmium. 
Flame-cleaning might not provide a satisfactory base for some specialist coatings. Flame-cleaned steel should 
be primed while it is still dry and warm but not hot. 
8.3.4.2.4 Manual preparation 
NOTE 1 Manual preparation includes the preparation of iron and steel using hand or powered tools such as wire brushes, chipping 
hammers, chisels, scrapers and vibratory-needle guns. 
8.3.4.2.4.1 Manual preparation is the least effective method of preparation and should not be used for 
steelwork exposed to severe or moderate conditions unless the size of the areas or other circumstances might 
preclude the use of more effective methods. Manual preparation does not provide a satisfactory base for 
specialist coatings and therefore especially formulated coatings, which are tolerant of poorly prepared 
surfaces, should be used.  
8.3.4.2.4.2 Manual preparation, whether with hand or power tools, is laborious and it is difficult to 
maintain a uniform standard for any length of time. Power tools usually give best results, but care should be 
taken to avoid surface damage such as burning, indentation, burring and scoring as peaks can be produced 
which protrude through the paint film and become focal points of corrosion. Over-vigorous brushing with hand 
or power tools should also be avoided as it can produce excessively burnished areas to which paint adhesion 
is poor.  
8.3.4.2.4.3 Weathering should not be employed as an alternative to more effective methods, such as 
abrasive blasting, in situations where complete removal of rust and scale is essential. 
NOTE 2 Reliance is often placed on weathering (i.e. exposure to the elements) to loosen millscale sufficiently to permit its removal 
by manual cleaning. However, weathering to the point where all the millscale has loosened can take many months, and it is rarely 
practicable to allow time for this. It is also unlikely that all the surfaces weather at the same rate, thus making it impossible to prepare the 
surface to a uniform standard. Also, in chemically polluted and marine atmospheres, lengthy exposure results in contamination of the 
surface and increased risk of corrosion. 
8.3.4.2.5 Removal of oil, grease and surface deposits 
8.3.4.2.5.1 In factory processes, oil and grease should be removed with hot alkali solutions, solvent 
emulsions or solvents, followed by thorough rinsing with water, or by steam cleaning or high-pressure water 
jets. Where possible, these methods should be used on site, but often all that can be done is to wipe the DRS 554: 2022 
55                ©RSB2023- All rights reserved 
 surface with a proprietary cleaning agent and a succession of clean swabs, taking care to avoid spreading the 
oil or grease over the surface.  
8.3.4.2.5.2 Surfaces which are contaminated following exposure in marine or chemically charged 
atmospheres should be washed with clean water, rinsed and allowed to dry before priming. Rust that develops 
as a result of washing should be removed. 
8.3.4.3 Priming 
NOTE 1 Table 4 lists and describes the primers for iron and steel in general use in conjunction with undercoats and finishes of 
conventional use. Typical applications are shown in Table 14. 
8.3.4.3.1 Zinc-rich epoxy primers (4/8) can be over coated with most other coating types, including most 
specialist coatings. Advice should be sought from the coating manufacturer when drying-oil/resin coatings are 
to be used over zinc-rich primers.  
8.3.4.3.2 Primers for iron and steel should be selected according to the type and standard of surface 
preparation and the conditions of exposure, including the time that is likely to elapse between pruning and 
completion of painting.  
8.3.4.3.3 Abrasive blasting provides a satisfactory base for all types of primers. When less effective 
methods are employed, notably manual cleaning, more tolerant primers, e.g. 4/5, 4/8, or 4/10, should be used. 
NOTE 2 When steelwork is blast-cleaned in the factory it is usual to combine this treatment with application of a prefabrication 
primer, e.g. a zinc-rich epoxy type (4/8). 
8.3.4.3.4 It is essential that priming follow preparation as quickly as possible and certainly on the same 
day, otherwise further corrosion can develop. The interval between preparation and priming is especially 
critical with blast-cleaned surfaces, and priming should follow preferably within 1 h and certainly within 4 h; if it 
is likely to be delayed beyond this, a temporary protective or holding primer, e.g. 4/1 or 4/2, should be applied.  
8.3.4.3.5 Primed surfaces should be overcoated as soon as possible. If there is likely to be a delay in 
applying further coats, the primer should be resistant to weathering and has to afford some protection to the 
surface. Most prefabrication primers and the tolerant types (see Table 4) can be left uncoated for a maximum 
of about 9 months depending upon the conditions of exposure and the effectiveness of the preparatory work. 
Other types of primers (including surface tolerant primers, i.e. 4/10, can be equally effective, but the 
manufacturer should be consulted on this aspect.  
8.3.4.3.6 Primed steelwork, especially if it has been exposed for a lengthy period, should be examined 
carefully before further coats of paint are applied. If the primer has deteriorated, e.g. is perished, eroded or 
poorly adhering, or has been damaged, so allowing corrosion to develop, the affected areas should be re-
prepared and primed. If there is evidence of widespread corrosion beneath the primer, it should be removed 
and the surface again prepared and primed.  
8.3.4.3.7 Oil, grease and surface deposits should be removed from primed surfaces as described in 
8.3.4.2.5. Removal of salt deposits by washing from surfaces pruned with zinc-rich primers is especially 
important as the corrosion products formed by reaction between the salts and the zinc can affect the 
performance of subsequent coats.   
©RSB 2023- All rights reserved                  56 
 8.3.4.3.8 With a single coat of primer, it is difficult to obtain films of uniform thickness and free from 
pinholes, the points at which corrosion starts. In all but mild interior exposure conditions, two coats of primer 
should be applied. However, where application of two coats cannot extend to the whole of the surface, a 
second coat should be applied to vulnerable points, e.g. along external angles and to bolts and rivet heads 
(stripe coating). When a factory-applied prefabrication primer has been used and a paint system of 
conventional type is to be applied, the second coat should be either a zinc phosphate (4/5), chromate (4/8) or 
water-borne acrylic (4/9) or a two pack surface tolerant primer (4/10). 
8.3.4.4 Coating systems for interior and exterior use 
8.3.4.4.1  General surfaces 
8.3.4.4.1.1 The number and type of coats applied after priming is determined by the protection and 
appearance requirements as well as by the properties of the individual coatings. Generally, the combined 
thickness of priming and finishes should be a minimum of approximately 125 μm for good protection in 
moderate exterior exposure conditions; any significant increase or decrease affects the protective properties 
and life expectancy of the coating proportionately. Alkyd finish systems of adequate thickness afford good 
protection in mild exposure conditions and offer a wide choice of colour. For exterior surfaces, gloss finishes 
should generally be used. 
NOTE 1 Aluminium paints (7/6), although giving rather thin films, have good protective properties and provide an economical finish 
for steel. They are also suitable for use on heated surfaces (see 8.3.4.4.2). 
NOTE 2 Micaceous iron oxide (MIO) paints (7/7) provide good protection and are widely used in situations where the limited range of 
colours in which they are available is not a disadvantage. However, they can be overcoated with compatible gloss finishes (with the 
manufacturer's approval). MIO paints of normal type provide films of substantial thickness, and there are also high-build types, usually 
applied by airless spray, giving films of even greater thickness. 
8.3.4.4.1.2 Bituminous and tar paints (see Table 10), if applied in thick films, provide good protection 
against fresh and salt water and some chemicals in situations where colour is not a requirement. When 
exposed to direct sunlight, they craze and chalk and should therefore be overcoated with bituminous 
aluminium paint. Generally, bituminous and tar paints should be applied over an inhibitive primer. The 
inhibitive primer should be allowed to harden (this can take several weeks) or a specially formulated primer 
should be used, as the solvents in some types of bituminous and tar paints can cause softening and lifting of 
the primer. 
NOTE 3 Table 14 indicates some typical coating systems for iron and steel in moderate exterior and interior exposure conditions. 
8.3.4.4.1.3 Specialist coatings, often in conjunction with metallic coatings, are usually necessary for 
severe conditions or where life expectancies in excess of those shown in Table 14 are required; in these 
circumstances, reference should be made to ISO 12944-5 and ISO 14713-1. 
8.3.4.4.2 Heated surfaces 
In addition to providing protection, paint systems applied to flues, chimneys, radiators, heating panels and 
other heated surfaces should have the appropriate degree of heat-resistance in accordance with ISO 12944-5 
or as follows. 
a) Up to about 50 °C. Normal paint systems as described in 8.3.4.4.1 (except bituminous and tar- based 
paints) are usually satisfactory (see Note).  DRS 554: 2022 
57                ©RSB2023- All rights reserved 
 b) 50 °C to 90 °C. Application of two coats of alkyd gloss finish or aluminium paint over primer as in a) is 
usually satisfactory; with coloured finishes, some discoloration of light colours can occur at the upper end 
of the range.  
c) 90 °C to 200 °C. Application of two coats of aluminium paint direct to clean bare metal is usually 
satisfactory although much depends upon the heating cycle. A coating that has withstood several months' 
exposure to temperatures at the higher end of the range can fail rapidly when the surface cools, especially 
if condensation occurs.  
d) Above 200 °C. Specialist coatings are likely to be required, and reference should be made to coatings 
manufacturers. 
NOTE Resistance to heat is influenced mainly by the maximum temperature reached in service and the nature of the heating cycle, 
i.e. where sustained or intermittent and whether the surface is exposed to moisture. The behaviour of the coating is also influenced by the 
extent to which the surface remains dry when cold. 
8.4 Non-ferrous metals and metallic coatings 
8.4.1 Characteristics 
8.4.1.1 General 
NOTE 1 Non-ferrous metals are more resistant to corrosion than iron and steel and, for this reason, are often used as alternatives. 
Some, notably zinc and aluminium, are used as protective coatings for iron and steel. 
8.4.1.1.1 In most conditions, painting is not necessary except for appearance, but might be needed in 
some exposure conditions, e.g. in acid or severe marine or road salt conditions.  
8.4.1.1.2 A characteristic of some non-ferrous metal surfaces is that special preparation or pre-treatment, 
or the use of primers of specific type, is always necessary to ensure satisfactory adhesion of paint. This is 
particularly so where thermally sprayed coatings are to be exposed externally where a sealer should be 
applied prior to priming and over coating with the specified paint system. 
NOTE 2 Preparatory and pre-treatment methods are described in 8.4.2 and priming in 8.4.3 
8.4.1.2 Metallic coatings 
8.4.1.2.1 Zinc and aluminium are used extensively as protective coatings, both individually and as alloys, 
for iron and steel structural members, sheets and components and consideration should be given to their use 
in moderate and severe exposure conditions and where long-term protection is required. 
NOTE ISO 14713 gives guidance on the selection and specification of metallic coatings. 
8.4.1.2.2 The different forms of coated product have a thickness or mass of coating, which depending on 
the product chosen should be selected to suit the expected severity of exposure or service requirements.  
8.4.1.2.3 The application of zinc and aluminium coatings to iron and steel should be as follows:  
©RSB 2023- All rights reserved                  58 
 a) hot-dip galvanizing (zinc) for general steelwork and fittings (for further information see ISO 14713) and 
claddings (for further information see ISO 9329-1);  
b) hot-dip aluminizing for the application of aluminium to steel;  
c) sherardizing (zinc) mainly for fittings, fasteners and small items (for further information see ISO 14713-3); 
d) electroplating (zinc) by electrolytic deposition of zinc from zinc salt solutions for small items (for further 
information see ISO 14713, parts 1-3), as well as for sheet components;  
e) metal spraying (zinc, aluminium or their alloys, sprayed in a semi-molten form) for structural steelwork and 
plates after abrasive blasting (for further information see ISO 2063) to be undertaken in the factory or, 
when conditions permit, on site. 
8.4.1.2.4 Metallic coatings may be painted under certain circumstances, such as for appearance or for 
added protection in some exposure conditions.  
8.4.1.2.5 Special preparation or pre-treatment, or the use of primers of specific type, is essential in order to 
ensure satisfactory adhesion of paint (see 8.4.2 and 8.4.3). Appropriate sealer or paint systems usually 
adhere satisfactorily to sprayed non-ferrous coatings ISO 12944 if they are applied soon after the sprayed 
coatings. 
8.4.2 Surface preparation for non-ferrous metals 
8.4.2.1 General 
8.4.2.1.1 Preparation of new non-ferrous metal surfaces is concerned essentially with the removal of dirt, 
grease and corrosion products and treatment to improve paint adhesion, e.g. to galvanized surfaces and to 
aluminium sheets and extruded sections.  
8.4.2.1.2 Sprayed metallic coatings and aluminium castings will provide satisfactory adhesion for paint, but 
the surfaces should be clean and free from corrosion products and might require light abrasion. Etch priming 
may be necessary to improve adhesion.  
8.4.2.1.3 Non-ferrous metals are often left unpainted for many years, but painting might eventually be 
necessary for appearance or to arrest deterioration. If aluminium is left unpainted it can acquire a rough layer 
of corrosion products that should be removed before painting. Similarly, if erosion of metallic zinc coating from 
a galvanized substrate has exposed the steel, any rust should be removed. However, if erosion of a thermally 
metal sprayed surface has exposed the steel, then the complete thermal sprayed coating should be removed 
prior to any painting. 
8.4.2.2 Degreasing 
Non-ferrous metals readily retain grease and lubricants used in extrusion and drawing processes and these 
should be removed. On site, after cleaning off any gross contamination with an appropriate cleaning fluid, e.g. 
a proprietary cleaning agent, surfaces should be washed using a detergent solution, rinsed and allowed to dry. 
Alternatively, surfaces should be wiped over with a proprietary cleaning agent and clean swabs; solvent and 
swabs should be changed frequently to avoid spreading the contaminant over the surface. In difficult cases 
more abrasive materials should be used. DRS 554: 2022 
59                ©RSB2023- All rights reserved 
 NOTE Degreasing of thermally metal sprayed coatings and sheradizing can lead to problems with subsequent paint coatings due 
to the porous nature of the coating, allowing absorption of the cleaning fluids which then remain trapped and can lead to premature 
breakdown of the paint coating. 
8.4.2.3 Removal of corrosion products 
8.4.2.3.1 Sprayed metallic coatings should be sealed (see 8.4.3.4) otherwise corrosion products can 
develop fairly rapidly, especially in damp or chemically-charged atmospheres. Corrosion products could be 
detrimental to the metallic coating and affect paint adhesion. They should be removed before painting by 
scrubbing with clean water and stiff bristle or nylon (not wire) brushes, followed by rinsing with clean water.  
8.4.2.3.2 Removal of the rough layer of corrosion products which can form on aluminium after several 
years exposure can be difficult and abrasion might be necessary, e.g. with stainless steel wire wool or nylon 
pads, using water as a lubricant. Mild steel, brass, or copper wire should not be used, as broken strands can 
become embedded in the surface and stimulate corrosion.  
8.4.2.3.3 If non-ferrous metallic coatings on iron and steel are damaged or become eroded on long 
exposure, rusting of the exposed base metal is likely to occur. Rusted areas should be cleaned to bright metal 
and roughened by wire brushing or abrasion, care being taken to avoid damage to the adjacent sound zinc or 
aluminium coating. 
8.4.2.4 Pre-treatment (wash or etching) primers 
NOTE 1 Although included here with other preparatory treatments, pre-treatment primers have some of the properties of a 
conventional metal primer in addition to their essential function of assisting adhesion of paint systems to non-ferrous metals. 
8.4.2.4.1 Pre-treatment primers are applied as thin films. The maximum film thickness specified by the 
manufacturer should not be exceeded. Except in very mild conditions, pre-treatment primers should be 
followed by a normal primer.  
8.4.2.4.2 The use of two-pack pre-treatment primers (4/1) which are generally superior to one-pack types 
(4/2) is now being replaced by water-based adhesion primers (4/4) and mordant solutions (4/3, see 8.4.2.5) as 
ways of improving the adhesion of subsequent coating systems to zinc surfaces. Some pre- treatment primers 
are sensitive to moisture in the early stages and their suitability for use in conditions where they are likely to 
be exposed to rain or dew should be checked with the manufacturer. 
NOTE 2 The use of etch primers (either simple or two pack) for hot-dip galvanized steel is rare. 
8.4.2.5 Chemical pre-treatments 
Zinc, aluminium and some other non-ferrous metals can be pre-treated to improve paint adhesion. Such pre-
treatment (e.g. phosphate) should be carried out under controlled, factory conditions. Site- applied treatments 
with proprietary washes can be less effective and can present difficulties in use, especially if final rinsing is 
required. A material for the pre-treatment of galvanized surfaces mordant solution (4/3), when properly 
applied, blackens zinc surfaces. If this does not occur, the surface should be thoroughly cleaned (see 8.4.2.3) 
and the treatment should be repeated. Excessive application of the wash (which, on horizontal surfaces can 
lead to ponding) and excessive thickness of coating should be avoided.  
©RSB 2023- All rights reserved                  60 
 8.4.2.6 Weathering 
Exposure of zinc and galvanized surfaces to weathering can improve paint adhesion, but the process is likely 
to take several months, even in conditions conducive to weathering, and the surface rarely weathers 
uniformly, making it difficult to determine whether the surface has weathered sufficiently to be painted. Also, 
surfaces are likely to become soiled or contaminated especially in severe or very severe exposure conditions, 
e.g. industrial and marine, and should be washed (and degreased if necessary) before paint is applied. 
Weathering is unnecessary if the correct pre-treatments and/or primers are used (see 8.4.3). 
8.4.2.7 Abrasion 
Adhesion of paint to non-ferrous metals can be assisted by abrading the surface with fine emery cloth, or 
abrasive paper and a proprietary degreasing agent; this method should be used for small areas prepared on 
site. Care should be taken not to abrade through thin films of pure aluminium on composite (clad) sheets; the 
use of steel wool or hard abrasives should be avoided on these surfaces. Light abrasion of galvanized 
surfaces by abrasive blasting (sweep blasting) can be effective at promoting the adhesion of subsequent 
coats of paint. It is important that a suitable, soft blast medium is used, with low blast pressures (< 276 MPa) 
and an optimized and controlled blasting angle and nozzle-to-work piece distance maintained. 
8.4.2.8 Anodizing 
This is an electrolytic process used on aluminium in which a corrosion-resistant oxide film is deposited on the 
surface. Anodizing can provide a satisfactory surface for painting, but the process is expensive and is rarely 
used solely to facilitate painting. The advice of the paint manufacturer should be sought. 
8.4.3 Priming 
8.4.3.1 General 
8.4.3.1.1 Primers for non-ferrous metals should contain corrosion-inhibiting pigments (see F.4.5) but some 
such pigments which can be found in primers for iron and steel, e.g. graphite, are unsuitable as they can 
stimulate corrosion.  
8.4.3.1.2 Film thickness, although it has to be adequate, need not be so critical to the protection of non-
ferrous metals as it is with iron and steel. In most conditions, one coat of primer in addition to the possible use 
of a pre-treatment primer provides a satisfactory base for further coatings; in some circumstances, a pre-
treatment primer alone might suffice. Special consideration should be given in certain micro- climates where 
soluble salts can collect on surfaces resulting in highly corrosive conditions where corrosion products are not 
removed by normal ram washing and the formation of a passivating film of relatively insoluble oxides and 
other salts is not formed. Under such conditions, a greater film thickness, similar to that required for the 
protection of iron and steel should be used. 
NOTE Recommendations in respect of primers for the non-ferrous metals in general use in buildings, assuming subsequent 
application of paints of conventional type, are described in 8.4.3.2, 8.4.3.3, 8.4.3.4, 8.4.3.5, 8.4.3.6 and 8.4.3.7. Surfaces, preparatory 
treatments and primers are correlated in Table 15. 
8.4.3.2 Aluminium and its alloy 
Although aluminium and its alloys vary in corrosion resistance, similar primers are used for all of them. Pre-
treatment primers should be used for aluminium and its alloys to assist adhesion on smooth surfaces, e.g. 
sheets, extruded sections and aluminized steel. DRS 554: 2022 
61                ©RSB2023- All rights reserved 
 8.4.3.3 Zinc and zinc-coated (galvanized, sherardized and electroplated) steel 
8.4.3.3.1 Zinc reacts with most drying-oil/resin paints, forming soluble salts (zinc soaps) beneath the paint 
film, which cause it to become embrittled and lose adhesion. The zinc should therefore be primed with a non-
oil based primer. Pre-treatment primers (4/1, 4/2) can be used except possibly on galvanized sheet. 
NOTE Unless otherwise specified (i.e. oiled or untreated), virtually all galvanized sheet produced is passivated to prevent wet 
storage staining (white rusting) during storage. Such a treatment is likely to prevent pre-treatment primers reacting fully with the zinc and 
it might also be incompatible with phosphate treatments. Galvanized sheet steel and components manufactured from such sheet, might 
need treatment with proprietary chemicals before pre-treatment or painting. Abrasion may be used to remove the original passivation 
treatment but care needs to be taken to avoid excessive removal of the zinc coating, which would reduce the protective value of the 
system 
8.4.3.3.2 Water-borne acrylic (4/9) and two pack surface tolerant (4/10) can also be used to prime zinc. 
Primers formulated for direct application to zinc surfaces are satisfactory subject to the use of compatible 
topcoats. 
8.4.3.4 Sprayed metallic coatings 
Where sprayed zinc, aluminium and zinc aluminium alloy coatings are to be painted, following their application 
they should be immediately coated with a pre-treatment primer, especially if they are to be exposed to damp 
or corrosive atmospheres; in order to retard the development of corrosion products which can affect the 
adhesion or appearance of the paint. If this is not done and corrosion products have developed, they should 
be removed (see 8.4.2.3) and the surface allowed to dry before application of the pre-treatment primer. Except 
in very mild conditions, the pre-treatment primer should be followed by one coat of compatible primer. 
8.4.3.5 Copper and its alloys (e.g. brass and bronze) 
Copper and its alloys are rarely painted except for appearance. To aid the adhesion of paint these surfaces 
should be abraded with fine abrasive paper, wiped with a proprietary degreasing agent, and then a pre-
treatment primer should be applied. Indoors, direct application of alkyd gloss after abrasion is usually 
satisfactory. Special materials are available if a clear finish is required. 
8.4.3.6 Lead 
Abrasion as described for copper (see 8.4.3.5), or treatment with phosphating solutions (see 8.4.2.5) should 
be undertaken to improve adhesion of paint to lead surfaces. Lead surfaces should not be abraded dry. Pre-
treatment primers and conventional metal primers, which do not contain graphite, should be applied to clean, 
grease-free surfaces. 
8.4.3.7 Chromium, nickel, tin and cadmium (as coatings) 
8.4.3.7.1 New chromium and nickel coatings rarely need painting, but it might be necessary if they become 
corroded. The surfaces should be lightly abraded to remove corrosion products before application of pre-
treatment primer.  
8.4.3.7.2 Tin plate presents few difficulties in painting; most paints adhere after degreasing and light 
abrasion of the surface.   
©RSB 2023- All rights reserved                  62 
 8.4.3.7.3 Cadmium should not be weathered prior to painting. Phosphate treatment (see 8.4.2.5) or a pre- 
treatment primer (after light abrasion if necessary) can improve adhesion of subsequent coats. Cadmium 
plated surfaces should not be abraded dry. 
8.4.4 Coating systems for interior and exterior use 
8.4.4.1 In most situations, alkyd finish systems can be used, but when they are to be applied to pruned 
galvanized surfaces, it should be ensured that the primer and succeeding coats are compatible, otherwise 
adhesion failure can occur, especially in wet conditions. Micaceous iron oxide paints can be used to provide 
added protection to galvanized and metal-sprayed steel in moderate and many severe conditions. Bituminous 
paints can be used for contact surfaces and where colour and appearance are not critical.  
8.4.4.2 Coatings for aluminium should not contain graphite pigments, which stimulate corrosion, as the 
priming coat might not isolate them from contact with the metal.  
8.4.4.3 Coating systems for non-ferrous metals are similar to those indicated for iron and steel in Table 
14, except that film thickness tends to be less critical and fewer coats can be used. In many moderate exterior 
and interior exposure conditions, three-coat systems (including primer) having a total thickness of about 85 
μm might be adequate; in some interior situations, thinner films should be used. The life expectancy of 
comparable paint systems on non-ferrous metals tends to be greater than on iron and steel.  
8.4.4.4 For guidance on the selection of paint coatings for galvanized and metal-sprayed iron and steel in 
severe exposure conditions, reference should be made to ISO 14713-1. 
8.5 Plaster, external rendering, concrete (including lightweight and autoclaved aerated 
blocks), brick and stone – General considerations 
NOTE Plaster, external rendering, concrete, brick and stone have a number of characteristics in common and, to avoid repetition, 
these and general principles applying to the selection of paint for these substrate systems are considered here. For further information on 
the protection of concrete structures, see ISO 16311 (Parts 1 - 4). 
8.5.1 Characteristics 
8.5.1.1 Moisture content 
Until the contained moisture has substantially dried out, there is some degree of risk in applying most types of 
coatings. Drying out can take a long time even in favourable conditions, a rough estimate being one week of 
good drying conditions for each 5 mm thickness of wet construction (typically 4 weeks to 6 weeks).  
Electrical moisture meters should be used to determine the moisture content of the substrate. They are easy 
and convenient to use and enable a number of readings to be taken quickly. If a wall is believed to be damp 
but meter readings at a shallow depth indicate low moisture content, the area should be covered with a sheet 
of polyethylene and rechecked 24 h later. If there is adjacent woodwork, its moisture content should be 
determined, as there is less likelihood of soluble salts being present in wood and so readings are more 
reliable, especially if they are significantly lower for the wood. 
NOTE 1 Water, often in large quantities, is used with all the materials referred to and can also be absorbed as a result of storage of 
materials in the open without protection. Excessive moisture affects the adhesion of most types of paints, causes blistering and flaking 
and encourages the growth of moulds. Additionally, in combination with alkalis and salts contained in many wet materials of construction, 
it is the cause of other difficulties in relation to painting, including efflorescence, alkaline attack and staining. DRS 554: 2022 
63                ©RSB2023- All rights reserved 
 NOTE 2 The first column in Table 16 and Table 17 refers to four stages of drying of walls, i.e. dry, drying, damp, and wet, and gives 
corresponding equilibrium humidity percentages. 
8.5.1.2 Efflorescence 
Efflorescence, usually sodium sulfate, is likely to disrupt relatively impermeable (e.g. solvent-borne) paints but 
can come through more permeable (e.g. water-borne) paints without much disruption although their adhesion 
might be impaired. It is undesirable, therefore, to apply even permeable paints until efflorescence has ceased. 
As it occurs, it should be removed with a dry cloth or brush, and collected in bags. This should be followed by 
wiping with a damp cloth wrung out frequently in clean water avoiding excessive wetting. This treatment 
should be repeated at intervals of a few days until efflorescence has ceased. A proprietary acid wash may 
also be used. 
8.5.1.3 Calcium carbonate deposits 
Thin, hard film known as lime bloom cannot be wiped off but can usually be softened and removed with a 
steam gun and scraper. Lime bloom can be over-painted without much risk of disruption provided the 
substrate is substantially dry. The glazed surface might impair adhesion and should be lightly abraded to 
prevent this. 
8.5.1.4 Alkalinity 
NOTE Materials containing Portland cement (CEM 1) or lime are strongly alkaline; gypsum plasters are not usually alkaline in 
themselves but might become so if they are gauged with lime or it is brought forward from backings during drying. Alkalinity diminishes 
with ageing, but the process can take several years with cement-based products. 
8.5.1.4.1 Drying-oil/resin paints are likely to be saponified (softened or liquefied) by alkalis in the presence 
of moisture. Water-borne paints are not attacked in this way but can be weakened or bleached by strong 
alkalis. Some special purpose paints, notably those based on chlorinated rubber or epoxy resins, are not 
attacked but may only be applied to dry substrates, and this usually precludes their use on new work. Cement-
based paints are also resistant to alkaline attack. Some pigments are attacked by alkalis, causing fading or 
discoloration, but paints intended for use on substrates that might contain alkalis are usually formulated with 
resistant pigments.  
8.5.1.4.2 Alkali-resisting primers (5/1) provide a measure of protection against alkaline attack and should 
be used beneath solvent-borne systems applied to substrates in which alkalis might be present. However, it 
cannot be too strongly emphasized that the essential function of primers is to dimmish the risk of failure on 
substrates that are substantially dry, and they do not obviate the need to allow time for this condition to be 
reached.  
8.5.1.4.3 Alkali-resisting primers can also improve the performance of water-borne paint on cement-based 
substrates; if so used, they should be applied thinly to avoid producing a glossy surface to which water-borne 
paint might not adhere satisfactorily. 
8.5.1.5 Staining 
NOTE Brown stains with no appreciable surface deposit sometimes appear on water-borne paints but do not normally affect 
solvent-borne paints. They are usually derived from substrates, notably certain types of brick, hollow clay pot or clinker block, containing 
soluble salts or colouring materials, or from sands containing biological matter that reacts with alkali.  
©RSB 2023- All rights reserved                  64 
 If it is suspected that brown staining is likely to occur, a coat of primer should be applied to prevent it and 
should also be used over stained water-borne paint to prevent staining of succeeding coats. The substrates 
should be substantially dry and, for the reason indicated in 8.5.1.4, the primer should be applied thinly. 
8.5.2 Coating systems for interior use 
8.5.2.1 General 
8.5.2.1.1 The choice of paint systems for substrates employing wet materials of construction should be 
determined by the moisture content at the time of painting. Where time is allowed for drying out, the conditions 
of service and the requirements in respect of appearance, i.e. colour, sheen level and texture, should be taken 
into account in the choice of paint systems.  
8.5.2.1.2 Mid-sheen or matt finishes should be used for walls and ceilings as they minimize the effect of 
surface irregularities and reduce reflection of light sources. Their resistance to wear and repeated washing is 
generally relative to the degree of sheen, and mid-sheen or matt finishes are less suitable than gloss finishes 
for use in hard-wear conditions. 
8.5.2.2 Mid-sheen and matt water-borne paints 
Mid-sheen and matt water-borne paints are permeable, reasonably resistant to alkaline attack and therefore 
suitable for use on substrates that are not completely dry, but they should not on this account be misused, e.g. 
applied to damp surfaces within a few days of plastering. Permeability is generally proportionate to the level of 
sheen; the matt contract types (7/5) are the most permeable although they are less resistant to wear and 
frequent washing than the other types. Water-borne paints applied to reasonably dry substrates usually 
provide a satisfactory base for most of the types of paint that might be required for maintenance painting. 
8.5.2.3 Solvent-borne alkyd finishes 
Solvent-borne alkyd finishes are less permeable and more susceptible to alkaline attack than their water-
borne paint counterparts and should be applied to completely dry substrates over a primer. These have good 
resistance to wear and frequent washing but should be applied only to dry primed substrates. If the conditions 
of service warrant the use of a solvent-borne gloss finish and there is insufficient time for drying out, water-
borne paint should be used as a temporary measure and the gloss finish system applied when drying out is 
complete. Use of solvent-borne finishes on large areas should be avoided as this can give rise to solvent 
vapour hazards. Breathing apparatus should be worn when using solvent-borne products.  
Note For further information on health and safety when working with solvent-borne products, see Annex B. 
8.5.2.4 Water-borne acrylic gloss finishes 
Water-borne wall paints have similar resistance to wear and frequent washing as their solvent-borne alkyd 
counterparts and minimize the health risks to the operator by reducing their exposure to solvent vapours. They 
have greater tolerance of substrate moisture and allow surfaces that are substantially dry (i.e. drying) to 
continue drying out. 
8.5.2.5 Textured coatings 
Textured coatings can be used for their decorative effect, to hide surface defects or irregularities and as an 
alternative to plastering or rendering. Coatings of this type include plastic-textured paints (7/15) and water-DRS 554: 2022 
65                ©RSB2023- All rights reserved 
 borne, heavy-textured masonry paints (7/9). They are usually relatively permeable and moderately resistant to 
alkaline attack and can be suitable for direct application to surfaces not completely dry, but reference should 
be made to manufacturer's recommendations. 
8.5.2.6 Multi-colour finishes 
Multi-colour finishes are very hardwearing and especially suitable for use on walls in circulating areas, 
cloakrooms and similar locations. Generally, they should be applied only to substantially dry substrates, 
usually over special primers or base-coats, but manufacturer's recommendations regarding surface conditions 
and systems should be followed. 
8.5.2.7 Cement paints 
Cement paints are permeable, resistant to alkaline attack and suitable for early application to most substrates 
except gypsum plaster, although their rough surface and limited colour range can preclude their use if ease of 
cleaning and decorative appearance is important. They can also impose limitations on the choice of 
maintenance paints. Cement paints should be applied directly without priming. 
8.5.2.8 Silicate-based masonry coatings 
The recommendations in 8.5.3.6 should be followed for silicate-based masonry coatings for coating systems 
for interior use. 
8.5.3 Coating systems for exterior use 
8.5.3.1 General 
8.5.3.1.1 Coating systems for exterior use are painted principally to enhance their appearance by imparting 
colour and texture or, in some cases, to prevent rain penetration. A range of specialized coatings (11/1 to 
11/4) can also be used, to protect the surface of concrete, etc. from potentially harmful agents, e.g. carbon 
dioxide, sulfur dioxide and salts and the manufacturer's recommendation should be followed. Initial painting 
and subsequent maintenance can be costly and, in designing new buildings, consideration should always be 
given to the use of alternative means of achieving the desired objectives, e.g. by using self-coloured 
renderings or facings which require infrequent maintenance or are resistant to ram penetration.  
8.5.3.1.2 Painting might be necessary to provide a uniform appearance when repairs or alterations have 
been carried out. Although external walls are often not painted until many years after erection, they should still 
be regarded as new; the considerations in respect of moisture content described in 8.10.1.1 should be 
applied, especially when rain has penetrated or repairs have been carried out. Additionally, mould and other 
biological growths might be present, and preparatory treatment to deal with these should be carried out as 
described in 11.5.8.  
8.5.3.1.3 It is essential that masonry paint not be used as a cure-all coating for rising damp, walls affected 
by water ingress from failed rainwater gutters and downpipes and failed lead flashing. It will fail very quickly in 
these circumstances. Preventive maintenance should be carried out first to overcome water ingress into the 
substrate before the application of coatings.  
8.5.3.1.4 Scaffolding should be positioned well off the work face to avoid patterning which is apparent once 
the scaffold rig is removed.  
©RSB 2023- All rights reserved                  66 
 8.5.3.2 Gloss finishes 
8.5.3.2.1 Gloss finishes are seldom used on external walls except in repainting work on smooth renderings 
or stucco. If solvent-borne gloss finishes are used, the substrate should be dry and an alkali-resistant primer 
should be applied.  
8.5.3.2.2 Water-borne gloss finishes should be used in suitable conditions of temperature and humidity for 
satisfactory film formation and drying. 
8.5.3.3 Mid-sheen and matt finishes 
Alkyd mid-sheen and matt finishes, as used for internal surfaces, are not suitable for external walls, where 
water-borne masonry paints (7/8) or, on substantially dry substrates, solvent-thinned masonry paints (7/10) 
should be used. 
8.5.3.4 Textured finishes 
NOTE Textured finishes are wide ranging from a fine sand or stone texture to heavy-texture coatings containing coarse aggregate 
or deriving their texture from the method of application. Examples of the types available are given in 7/8 to 7/11. 
8.5.3.4.1 Textured coatings should be used where greater durability is needed. The thicker or more heavily 
textured coatings also help to hide surface irregularities, fill fine surface cracks and contribute to the rain 
resistance of external walls. They should not be used to improve the acoustic or thermal insulation properties 
of walls as they are too thin. They can be used to prevent reduction of the original thermal insulation value by 
reducing rain penetration.  
8.5.3.4.2 Dirt pick-up could be a problem with the heavier textures in polluted atmospheres although the 
rough texture tends to promote an evenness of soiling that might be less apparent than on a smooth surface. 
Some thick, textured sprayed coatings are applied by specialist applicators and might be offered with a 
warranty as to their durability; because of the wide range of types and compositions available, manufacturer's 
recommendations should be ascertained. 
8.5.3.5 Cement paints 
On external exposure, algal growth is prone to develop on cement paints applied to surfaces that are 
persistently damp although some paints incorporate a fungicide. Cement paints should not be used in acidic 
exposure conditions. 
8.5.3.6 Silicate-based masonry coatings 
NOTE Silicate-based masonry coatings (mineral paints) have been used in continental Europe for a considerable time in grades 
suitable for external and internal surfaces. These coatings provide inert non-flammable films that do not support fungal and algal growth 
and are compatible with all mineral building materials. Compositions of high water vapour permeability are available. 
External surfaces to be painted should be free from dirt and all previous paint coatings. Application should be 
by brush, roller or spray. The drying coating can be susceptible to rain damage. The liquid paints are highly 
alkaline and hence precautions should be taken during application. DRS 554: 2022 
67                ©RSB2023- All rights reserved 
 8.6 Plaster 
8.6.1 Characteristics 
8.6.1.1 General 
The plasters in general use for internal work should comprise one or more of the following:  
a) calcium sulfate (gypsum) types, other than lightweight plasters, conforming to BS 1191-1 (see 8.6.1.2);  
b) calcium sulfate (gypsum) lightweight plasters conforming to BS 1191-2 (see 8.6.1.2);  
c) thin-wall plasters (see 8.6.1.3); d) cement plasters (see 8.6.1.4); e) lime plasters (see 8.6.1.5). 
NOTE For further information on plaster, see Annex I. For further information on plasterboard, see Annex J. 
8.6.1.2 Calcium sulphate (gypsum) plasters 
Used neat and when fully dry and set, calcium sulfate (gypsum) plasters can be painted without difficulty with 
most types of paint. Added lime (or cement in backing coats), in the presence of moisture, might cause 
alkalinity, and therefore an alkali-resistant coating should be used. 
8.6.1.3 Thin-wall plasters 
Thin-wall plasters are based on organic binders and to dry out rapidly are used in thin layers. They normally 
present no difficulties in painting when used on dry backings but sometimes appear underbound and can be 
excessively absorbent; in these cases, treatment as described in 8.6.2.4 should be carried out. 
8.6.1.4 Cement plasters 
Cement: sand or cement: sand: lime plasters should be used where strong, hard or moisture-resistant 
surfaces are needed. They should not be painted until they have substantially dried out, as they are strongly 
alkaline and likely to attack drying-oil/resin paints. 
8.6.1.5 Lime plasters 
Lime plasters should not be painted until they have substantially dried out, as they are strongly alkaline and 
likely to attack drying-oil/resin paints. 
NOTE Non-hydraulic lime plasters made with high-purity lime and clean sand are free from soluble salts and caustic alkali but can 
react with salts from backing to form caustic alkalis which attack drying-oil/resin paints and some water-borne paints if they are applied 
before the plaster has substantially dried out. Hydraulic lime plasters are variable in caustic alkali content and can attack paints severely.  
©RSB 2023- All rights reserved                  68 
 8.6.2 Surface preparation and priming of plaster 
8.6.2.1 Cleaning 
Dirt and loose surface deposits should be removed by dry brushing. Plaster nibs and splashes should be 
scraped off, care being taken to avoid damaging the surface. Efflorescence, if present, should be treated as 
described in 8.5.1.2. Mould growth can occur on plastered surfaces if drying out has been prolonged, 
especially in conditions of poor ventilation. The affected areas should be treated as described in 11.5.8.3. 
8.6.2.2 Treatment of stains 
For the treatment of stains, the recommendation in 8.5.1.5 should be applied 
8.6.2.3 Stopping and filling 
Cracks, holes and surface imperfections should be stopped and filled with plaster, water-mixed filler or, in 
cement plasters, with masonry cement, before application of first or priming coats. 
8.6.2.4 Priming 
NOTE Recommendations for priming are given in Table 16. 
8.6.2.4.1 Priming is essential when solvent-borne paint systems are applied to plaster; it is not usually 
necessary with water-borne paints, but see 8.5.1, in particular 8.5.1.4 and 8.5.1.5.  
8.6.2.4.2 When water-borne paints are applied to plaster of high or variable porosity, differential absorption 
can cause difficulties in application or variations in colour or sheen, which can persist through several coats. A 
well-thinned first coat of water-borne paint, sometimes referred to as a sealing or mist coat, often overcomes 
the problem but is likely to have relatively poor opacity and, if it is required, should be regarded or specified as 
an additional coat in the system. Where this proves inadequate a coat of alkali-resisting primer (5/1) or primer-
sealer (5/3) should be applied, but this should be done only if the substrate is substantially dry. The primer or 
primer-sealer might need thinning to ensure that it does not provide a glossy surface to which water-borne 
paint might not adhere satisfactorily. 
8.6.3 Coating systems for plaster 
The selection of coating systems for plaster should be in accordance with 8.5.2 and 8.5.3, and details of 
systems are incorporated in Table 16. 
8.7 External rendering 
8.7.1 Characteristics 
8.7.1.1 Cement rendering 
The renderings in general use are cement-based and might incorporate hydrated lime. They might not require 
painting when new, although this might eventually be necessary for appearance or if repairs are carried out. DRS 554: 2022 
69                ©RSB2023- All rights reserved 
 However, they should not be painted until they have substantially dried out, as they are strongly alkaline and 
likely to attack drying-oil/resin paints. 
8.7.1.2 Stucco 
Where deterioration or removal of the paint coating exposes the original surface, repainting might be 
undertaken. In order for repainting to be undertaken, the rendering should be sound and dry. 
NOTE Stucco can be made from lime/sand (pre 1790), Roman or Portland cement-based (dating from about 1790) or oil mastic 
(1790 to 1820). 
8.7.1.3 Repairs to renderings 
If repairs to old renderings, including stucco, are necessary, they should be carried out in accordance with BS 
5262, using cement-based mixes. The repaired portions should then be treated as for new work in respect of 
painting. 
8.7.2 Coating systems for external renderings 
8.7.2.1 Surface preparation 
8.7.2.1.1 Cleaning 
New surfaces normally should be brushed down with stiff (not wire) brushes to remove loose material. 
Efflorescence should be treated as described in 8.5.1.2. Old unpainted surfaces, especially if rough or 
textured, might require more rigorous treatment, including washing down, to remove accumulated dirt before 
painting. If washing is necessary, time should be allowed for drying out. Biological growths might be present 
on old surfaces and should be treated as described in 11.5.8. 
8.7.2.1.2 Treatment of stains 
The recommendations given in 8.5.1.5 should be applied for the treatment of stains. 
8.7.2.1.3 Stopping and filling 
Minor cracks, holes and surface defects should be made good with exterior grade water-mixed cement-based 
filler or masonry cement before application of the primer or first coat of paint. 
8.7.2.2 Priming 
NOTE Recommendations for priming are given in Table 17. 
8.7.2.2.1 When solvent-borne paint systems are to be applied, external renderings should be primed; it is 
not usually necessary with water-borne paints but see 8.5.1.4 and 8.5.1.5. This should be confirmed with the 
paint manufacturer.   
©RSB 2023- All rights reserved                  70 
 8.7.2.2.2 To accommodate variations in surface porosity and assist application, primers or first coats can 
be thinned in accordance with the manufacturer's instructions. 
8.7.2.3 Finishing 
The selection of coating systems for external renderings should be in accordance with 8.5.3, and details of 
systems are incorporated in Table 17. 
8.8 Concrete 
8.8.1 General 
8.8.1.1 Concrete does not usually require painting for protection although this might be necessary to 
prevent long-term deterioration in aggressive atmospheres. Protective painting, using chemical-resistant 
paints, might also be necessary to prevent further penetration of carbon dioxide, water and salts after repair of 
deteriorated concrete, or even on new concrete if the thickness and integrity of concrete over reinforcement is 
insufficient to provide protection. In most circumstances, however, concrete is painted to improve its 
appearance, especially on large areas.  
8.8.1.2 In relation to painting, the general characteristics of concrete are similar to those of external 
rendering. Because of the greater thicknesses usually involved, it can take concrete much longer to become 
dry enough to paint without restrictions on the choice of paints. The surface finish of concrete can vary widely 
from smooth and dense (e.g. with pre-cast components) to rough and porous with large voids. Specialist 
advice should be sought in cases where it is difficult to achieve a good, uniform coating unless a suitable filler 
or sealer has been used.  
8.8.1.3 Residues of release agents present on the surface of cast and shuttered concrete can seriously 
impair the adhesion of paints and should be removed. Laitance on trowelled and floated surfaces can also 
impair adhesion and should be removed. 
8.8.2 Coating systems for concrete 
8.8.2.1 Surface preparation/cleaning 
8.8.2.1.1 On new surfaces, deposits and loose material, including laitance, should be removed by scraping 
and brushing with stiff (not wire) brushes. On large areas, it might prove more effective to abrasive blast 
surfaces (using non-ferrous abrasives) to remove laitance and glaze on shuttered surface and expose fine 
aggregate. On smooth, shuttered surfaces, paint adhesion might be enhanced when roughened by abrasive 
blasting. If efflorescence is evident, it should be treated as described in 8.5.1.2. 
8.8.2.1.2 Residues of release agents should be removed with detergents or emulsifying agents rather than 
with solvents, which can simply spread the contaminant.  
8.8.2.1.3 Old unpainted surfaces might require washing to remove accumulated dirt before painting; if this 
is necessary, time should be allowed for drying out before painting. Surfaces on which biological growths are 
present should be treated as described in 11.5.8. DRS 554: 2022 
71                ©RSB2023- All rights reserved 
 8.8.2.2 Stopping and filling 
Large voids and air-holes should be filled with masonry cement or epoxy resin mortars. Minor surface defects 
should be made good with interior or exterior grade water-mixed cement-based filler or with masonry cement. 
Application of cement paint or bagging with a cement:sand slurry can reduce surface roughness and fill minor 
imperfections. 
8.8.2.3 Priming 
NOTE Recommendations for priming are given in Table 16 and Table 17. 
8.8.2.3.1 When solvent-borne systems are used on concrete a primer should be applied; it is not usually 
necessary with water-borne paints but see 8.5.1.4 and 8.5.1.5. This should be confirmed with the paint 
manufacturer.  
8.8.2.3.2 To accommodate variations in surface porosity and assist application, primers or first coats can 
be thinned in accordance with the manufacturer's instructions. 
8.8.2.4 Finishing 
8.8.2.4.1 The selection of coating systems for concrete should be in accordance with 8.5.2 and 8.5.3, and 
details of systems are incorporated in Table 16 and Table 17.  
8.8.2.4.2 Coatings which are applied to give additional protection should be of an impervious type, e.g. 
bituminous or other specialized coatings (7/8, 7/10, Table 10 and Table 11), to prevent ingress of water, 
corrosive salts and gases; and should be applied only to dry surfaces.  
NOTE By protecting the integrity of the concrete cover over mild or high-tensile steel reinforcement, the time to initiation of 
disruptive corrosion is extended, as well as reducing the rate of further deterioration of repaired existing concrete.  
8.8.2.4.3 Periodic maintenance is needed. Further guidance on the selection of specialist coatings for the 
protection of concrete both new and repaired is given in BS EN 1062-1 and BS EN 1504-2. 
8.9 Brick and stone 
8.9.1 Characteristics 
8.9.1.1 Bricks and stone are durable materials, generally of attractive natural appearance and, when 
new, do not usually require painting. 
NOTE 1 For information on the characteristics of brick and stone, see Annex K. 
8.9.1.2 On older buildings, painting might be necessary to improve appearance, hide repairs and 
alterations or reduce rain penetration. On large buildings, painting of external masonry essentially for cosmetic 
reasons should be undertaken only after consideration of the implications in respect of maintenance 
expenditure.   
©RSB 2023- All rights reserved                  72 
 8.9.1.3 Generally, brick (other than concrete bricks) and stone are not, in themselves, alkaline, but the 
mortars used in construction are usually strongly alkaline and, until dry, are likely to give rise to the difficulties 
in painting described in 8.5.1.4. Efflorescence can also occur on brickwork and stonework and should be 
treated in accordance with 8.5.1.2. 
NOTE 2 Where external brickwork and stonework are exposed to severe weathering conditions, e.g. in parapet, freestanding and 
retaining walls and below ground level damp-proof courses, it is difficult to ensure that moisture does not penetrate. 
8.9.1.4 If moisture penetration occurs, paint coatings are likely to be disrupted; also, they can prevent or 
retard drying out of moisture and thereby increase the risk of the brick or stone being damaged by frost. It is 
recommended that, in these situations, brickwork and stonework should not be painted. Concrete blocks are 
strongly alkaline and an alkali-resisting system should be used preferably when the brickwork has 
substantially dried out.  
8.9.1.5 The adhesion of conventional paints to the harder, non-porous stones, especially if the surface is 
smooth or polished, is likely to be poor and, if painting is essential, paints of the types recommended for 
glazed bricks (see 8.14.2) should be used. Where bricks contain high levels of ferrous oxide, a stain block 
primer should be used for sealing. 
NOTE 3 Some bricks can contain high levels of ferrous oxide which can be present in the raw materials, in certain parts of the 
country. This can cause iron staining which will bleed through most water-borne coatings. 
8.9.2 Coating systems for bricks and stone 
8.9.2.1 Surface preparation/cleaning 
New surfaces, e.g. fair-faced brickwork, should be brushed down with stiff (not wire) brushes to remove loose 
material. Efflorescence should be treated as described in 8.5.1.2. Heavily soiled and old unpainted surfaces 
might require more vigorous treatment, including high pressure washing down, to remove accumulated dirt. 
Cleaning should be carried out in accordance with BS 8221-1. When washing has been carried out, time 
should be allowed for drying out before painting. Biological growths might be present on old external surfaces 
and should be treated as described in 11.5.8. 
8.9.2.2 Stopping and filling 
8.9.2.2.1 On old, unpainted surfaces, repairs and re-pointing should be carried out well in advance of 
painting to facilitate drying out.  
8.9.2.2.2 Minor surface defects should be made good with ulterior or exterior grade water-mixed filler or 
with masonry cement. 
8.9.2.3 Priming 
NOTE Recommendations for priming are given in table 16 and table 17. 
8.9.2.3.1 Priming is necessary with solvent-borne systems and, because mortar joints are likely to be 
alkaline, an alkali-resisting primer should be used.  
8.9.2.3.2 Priming is not usually necessary with water-borne paints, but see 8.5.1.4, 8.5.1.5 and 8.9.1. This 
should be confirmed with the paint manufacturer.  DRS 554: 2022 
73                ©RSB2023- All rights reserved 
 8.9.2.3.3 To accommodate variations in surface porosity and facilitate application, primers or first coats 
should be thinned strictly in accordance with the manufacturer's instructions. 
8.9.2.4 Finishing 
The selection of coating systems for brick and stone should be in accordance with 8.5.2 and 8.5.3, and details 
of coating systems are incorporated in Table 16 and Table 17. 
NOTE Further guidance on surface protection systems for concrete is given in BS EN 1504-2. 
8.10 Precast concrete blocks 
NOTE for further information on concrete blocks, see annex K. 
8.10.1 Characteristics 
8.10.1.1 Moisture content 
To minimize drying shrinkage, blocks should be kept as dry as possible, particularly during site storage. The 
moisture content of new blockwork is unlikely to cause serious difficulties in painting but time should be 
allowed for drying out of the mortar joints before painting. 
8.10.1.2 Alkalinity 
New concrete blocks are strongly alkaline and an alkali-resisting system should be used preferably when the 
blockwork has substantially dried out. 
8.10.1.3 Porosity 
Concrete blocks vary considerably in porosity and absorption according to their manufacturing process, 
density and the nature of the aggregate used, but even the densest blocks are usually sufficiently porous to 
afford satisfactory adhesion for paint. The more open and porous materials, however, need a more protective 
system in exposed situations. Primers or first coats should be thinned in accordance with the manufacturer's 
instructions. 
8.10.1.4 Texture 
Blockwork is often painted directly to save the cost of rendering or plastering, but it should be appreciated that 
normal paint systems do not completely mask the texture of the blocks and attempting to smooth the surface 
by conventional filling methods is rarely satisfactory. Roller or spray application of heavy-bodied, thick 
coatings (7/9 or 7/11) can usefully combine both protective and aesthetic functions. When appearance is 
important, blocks having an acceptable surface texture, e.g. of facing quality, should be used, paint being 
used to complement the texture rather than mask it.  
©RSB 2023- All rights reserved                  74 
 8.10.2 Coating systems for precast concrete blocks 
8.10.2.1 Surface preparation/cleaning 
The surface of precast concrete blocks should be brushed down with stiff (not wire) brushes to remove loose 
material. Efflorescence, if present, should be treated as described in 8.5.1.2. 
8.10.2.2 Stopping and filling 
8.10.2.2.1 If necessary cracks, holes and damaged areas should be made good with cement mortar, 
masonry cement, or, in dry interior conditions, with water-mixed fillers.  
8.10.2.2.2 As indicated in 8.10.1.4, overall filling of the surface of blockwork by conventional methods is not 
recommended. On the finer-surfaced blocks, a cement/sand slurry or cement paint scrubbed into the surface 
reduces texture and fills small holes. Thick textured coatings are also useful in this respect (7/9 and 7/11). 
8.10.2.3 Priming 
NOTE Recommendations for priming are given in Table 16 and table 17. 
Priming is necessary with solvent-borne paint systems, and an alkali-resisting primer should be used. Priming 
is not usually required when water-borne paints are used, but see 8.5.1.4 and 8.5.1.5. This should be 
confirmed with the paint manufacturer.  
To accommodate variations in surface porosity and assist application, primers or first coats can be thinned in 
accordance with the manufacturer's instructions. 
8.10.2.4 Finishing 
The selection of coating systems for concrete blockwork should be in accordance with 8.5.2 and 8.5.3, and 
details of coating systems are incorporated in Table 16 and Table 17.  
NOTE Further guidance on surface protection systems for concrete is given in BS EN 1504-3. 
8.11 Cement-based sheets, boards and components 
WARNING Materials containing asbestos are subject to the legislation that requires precautions to be taken in handling them to ensure 
that they do not constitute a hazard to health (see Annex B). Cement-based insulating materials containing asbestos fibre, if found, 
should not be disturbed. Unknown cement-based insulating materials should be treated as containing asbestos fibre until properly 
identified. Specialist advice should be sought on the treatment of all asbestos containing materials and if necessary the correct method for 
its safe removal and disposal. DRS 554: 2022 
75                ©RSB2023- All rights reserved 
 8.11.1 Coating systems for cement-based sheets, boards and components 
8.11.1.1 Surface preparation/cleaning 
8.11.1.1.1 New surface surfaces should be brushed down with stiff (not wire) brushes to remove loose 
material. With materials containing asbestos, precautions to prevent inhalation of dust are essential (see 
WARNING to 8.11 and Annex B).  
8.11.1.1.2 Biological growths might be present on old, unpainted external cladding and roofing materials; if 
so, the surfaces should be treated as described in 11.5.8. 
8.11.1.2 Stopping and filling 
8.11.1.2.1 The necessity for filling does not normally arise with external cladding and roofing materials or 
with internal linings when patent fixing methods are used. When internal linings are fixed by nailing or 
screwing, a water-mixed filler (see 7.4.4) should be used for stopping.  
8.11.1.2.2 Where a high standard of finish is required on flat internal surfaces, smooth-surface boards 
should be specified but, if necessary, water-mixed fillers can be used. 
8.11.1.3 Priming 
NOTE Recommendations for priming are given in Table 16 and Table 17. 
8.11.1.3.1 Alkali-resisting primers might not be strictly necessary in solvent-borne paint systems for some 
types of cement-based insulating boards of low alkalinity, but there is no disadvantage in their use.  
8.11.1.3.2 Alkali-resisting primers of conventional type, as normally used in solvent-borne paint systems, 
should not be used under chlorinated or acrylated rubber paints (see 8.11.1.5). The latter should be applied 
directly to the surface or over a chlorinated or acrylated rubber-based primer, as recommended by the paint 
manufacturer.  
8.11.1.3.3 Asbestos-cement goods vary in porosity, and cement-based insulating boards can be highly 
porous. Primers or first coats should be thinned strictly in accordance with the manufacturer's instructions to 
accommodate variations in surface porosity and facilitate application. 
8.11.1.4 Back-painting 
Under certain circumstances, as indicated in K.3.2, fibre-cement sheets should be back-painted to prevent 
differential carbonation. For this purpose, impermeable paints of similar type to those used on the exposed 
surface should be used; alternatively, a cheaper material, e.g. bituminous paint, can be applied. 
8.11.1.5 Finishing 
The types of coating system described in 8.5.2 and 8.5.3 and the systems shown in Table 16 and Table 17 
are suitable for use on cement-based sheets, boards and components. If, however, a gloss or semi-gloss 
finish is required for asbestos-cement roofing and cladding sheets and components, chlorinated or acrylated  
©RSB 2023- All rights reserved                  76 
 rubber paint (which does not require an alkali-resisting primer) should be applied in preference to the system 
of alkali-resisting primer, undercoat and finish used with gloss finishes of conventional type. 
8.12 Paper and wallcoverings including plasterboard 
8.12.1 Characteristics 
8.12.1.1 General 
Problems can be experienced in respect of painting existing coloured wallcoverings.  
NOTE For information on general characteristics of paper wallcoverings and plasterboard, see Annex J. 
8.12.1.2 Wallpapers 
8.12.1.2.1 The metallic inks used in some patterns can react with water-borne paints and cause 
discoloration. In the past, wallpapers containing "gold" or red colours in their pattern, often gave rise to 
discoloration. Therefore, a test area should be painted on such papers to see if discoloration occurs; if it does, 
a solvent-borne primer or knotting should be applied to seal the surface of the paper (see 8.12.1.3) or the 
paper should be removed.  
8.12.1.2.2 It should be appreciated that application of paint to wallpaper makes its removal more difficult, 
should this be necessary at a later date, especially if solvent-borne paints are used. Wallpaper should be 
painted only if it is firmly adhering and without blisters, creases or prominent joins. 
8.12.1.3 Vinyl wallcoverings 
8.12.1.3.1 These can be vinyl-faced (e.g. paper-backed) or sheet vinyls. Vinyl wallcoverings can be painted, 
but migration of plasticizer from the vinyl into the paint coating could cause softening or the development of 
glossy patches in mid-sheen finishes. It is not possible to assess the likelihood of this by short-term tests and, 
in cases of doubt, the manufacturer of the wallcovering and/or paint should be consulted.  
8.12.1.3.2 Vinyl wallcoverings should be removed by lifting a corner and peeling away the vinyl coated 
surface layer. The remaining sheet can be used as a sub-surface for painting provided the surface adhesion is 
sound. 
8.12.1.4 Non-woven papers or vinyl coated non-wovens 
Non-wovens are wallcoverings containing a proportion of synthetic content. Non-woven papers or vinyl coated 
non-wovens allow for virtually direct removal in a single dry strippable sheet. Any issues such as metallic inks 
or plasticizer migration arising (as described in 8.12.1.2 or 8.12.1.3) should be resolved by removing the 
wallcovering. 
8.12.2 Removal of paper and wallcoverings 
In order to assess how much time is needed for the removal of the paper and wallcoverings, the following 
information should be included in the specification:  DRS 554: 2022 
77                ©RSB2023- All rights reserved 
 a) type of paper/wallcovering being removed;  
b) whether the paper and wallcoverings have been painted;  
c) the number of layers to be removed. 
8.12.3 Coating systems for paper, wallcoverings and plasterboard 
8.12.3.1 Surface preparation 
8.12.3.1.1 Newly-hung lining paper and wallcoverings should be allowed to dry out completely before 
painting. Dry surfaces should be lightly brushed to remove loose material. 
8.12.3.1.2 With existing wallcoverings, loose material should be refixed with the recommended adhesive; if 
adhesion is generally suspect, painting makes it worse and the wallcovering should be removed.  
8.12.3.1.3 Wallcoverings affected by mould growths should be removed and the source of the mould 
investigated. Subsequently, the surface should be treated as in 11.5.8.3.  
8.12.3.1.4 If water-borne paints are to be used and there is a risk of discoloration (see 8.12.1.2), a test area 
should be coated with the paint it is proposed to use and should be inspected after 24 h. If discoloration 
occurs, it can be prevented by applying a coat of knotting (see 7.4.3) or solvent-borne primer (5/1 or 5/3) 
overall or to the areas responsible. Alternatively, the wallcovering should be removed. 
8.12.3.2 Joint treatment 
8.12.3.2.1 Other than in plasterboard dry-lining systems, it is not possible to hide joints satisfactorily with 
conventional paint systems of normal thickness, and it is usually recommended that they should be featured, 
e.g. by using bevel-edged boards or cover strips.  
8.12.3.2.2 Plasterboard dry-lining systems employ tapered-edge boards, enabling a smooth, seamless 
surface to be obtained by taping and filling the shallow trough formed by abutting edges. The process can be 
carried out manually or mechanically. It is possible that if a standard decorative paint is used directly onto dry 
lining, that a textural difference will be seen between the caulked and sanded joints, and the paper 
plasterboard surface. Slurry coats and purpose made primers can be used to assist in disguising the 
difference in texture, and will also aid to even out the porosity of the substrate prior to painting. 
NOTE Recommendations for internal plastering are given in BS 5492. Recommendations for dry lining and partitioning using 
gypsum plasterboard are given in BS 8212. 
8.12.3.3 Priming 
Water-borne paints are usually applied direct to paper and other wallcoverings the exception being that a 
purpose designed primer should be used when there is a risk of discoloration on existing coloured wallpapers.  
©RSB 2023- All rights reserved                  78 
 8.12.3.4 Finishing 
Paper, vinyl, hessian and woven glass fibre surfaces are usually coated with water-borne paints. For improved 
wear resistance, acrylic water-borne paint should be used. 
8.13 Plastics 
8.13.1 General 
8.13.1.1 Typical examples of plastics in buildings include unplasticized polyvinyl chloride (PVC-U) 
cladding, rainwater goods and window frames; glass reinforced polyester (GRP) cladding and mouldings; and 
a variety of plastics coatings for metal.  
8.13.1.2 These materials generally have good durability, but the effects of weathering, soiling and 
mechanical damage over a number of years might suggest painting as a means of restoring the original 
appearance. Occasionally, premature deterioration occurs, and painting can then prove cheaper than 
replacement or, in the case of plastics coatings, can be necessary to prevent deterioration of the substrate. 
However, probably the most frequent reason for painting is to change the colour, especially with components, 
such as PVC-U rainwater goods, available in a very limited range of colours. 
NOTE For more detailed information, see BRE Information Paper 11/79 
8.13.1.3 If painting is considered as a method of restoring defective or deteriorated surfaces, specialist 
advice should be sought.  
8.13.1.4 Other plastics surfaces that might need painting for decorative purposes are expanded 
polystyrene and vinyl wallcoverings. 
8.13.2 PVC-U components 
8.13.2.1 Painting new unplasticized polyvinyl chloride (PVC-U) with certain types of building paints can 
reduce the impact resistance. Specialist coatings have been developed and should be used to introduce new 
colour or rectify discoloration if it occurs. On ageing, PVC-U becomes brittle, abrasion of new PVC-U also 
reduces its impact resistance and should be avoided. Surfaces, new or weathered, should be prepared for 
painting by washing with warm detergent solution, rinsing with clean water and drying.  
8.13.2.2 In addition to specialist coatings, PVC-U can be painted with some water-borne paints, which 
have been formulated to have good adhesion. Manufacturer's recommendations should be followed. PVC- U 
should not be painted in a colour significantly darker than its original colour otherwise heat absorption is 
increased if exposed to direct sunlight.  
8.13.2.3 Paints of conventional type can perform satisfactorily on PVC-U, but subsequent maintenance 
painting at intervals of 3 years to 5 years might be necessary, thus negating an important advantage of 
plastics, i.e. a reduction in the frequency of maintenance. This might not be of significance where the areas 
are small and adjacent surfaces of traditional materials require maintenance painting at relatively short 
intervals. However, consideration should be given to the use of long-life coatings on large areas such as 
cladding. Long-life coatings are usually of specialist type, e.g. two-pack polyurethanes or epoxies, but 
specialist advice should be sought. DRS 554: 2022 
79                ©RSB2023- All rights reserved 
 8.13.3 GRP components 
8.13.3.1 Most paints can be used on glass reinforced polyester (GRP) components. Surfaces should be 
prepared by thorough scrubbing with warm detergent solution and a stiff bristle brush or nylon pad (not wire 
wool, which can cause rust stains) followed by rinsing and drying. For heavy contamination, a proprietary 
degreasing solution might be needed.  
8.13.3.2 As with PVC-U, consideration should be given to the maintenance aspects of painting GRP and 
the use of long-life coatings in certain circumstances. Although GRP is less sensitive to solar gain than PVC-
U, the use of light-coloured finishes is recommended. 
8.13.4 Plastics coated metal 
8.13.4.1 General 
8.13.4.1.1 A wide variety of organic coatings, classifiable as plastics, are used on metal cladding and other 
components. These can be overcoated (post-applied coating) for aesthetic or maintenance purposes at or 
near end of life. The individual types vary and include polyvinyl chloride (PVC) plastisol, polyvinylidene fluoride 
(PVF2 or PVDF), polyester and polyurethane. Powder coatings such as epoxy, polyurethane, polyester or 
silicone modified versions are also found.  
8.13.4.1.2 It is essential that the pre-coating be identified to enable the application of a correctly adhering 
overcoating system, to be applied with or without a primer. Visual identification is not straightforward, but older 
PVC exhibits a characteristic ripple and polyester can be glossy, the others all appear smooth and generally 
matt. Fourier transform infrared (FTIR) spectroscopy should be used to identify samples from site. 
Manufacturers provide information on suitable primers and top coat(s) and this should include provision for 
painting any bare metal, e.g. edges or patches. 
8.13.4.2 Identification 
8.13.4.2.1 When identification is not possible, a site adhesion test should be undertaken with the range of 
primers available and also a direct application. The test should be done on cleaned areas and in accordance 
with the coatings and the manufacturer's instructions. 
NOTE This might involve leaving the overcoating systems for up to 7 days to allow adhesion to develop via plasticizer linkage on 
PVC for example. 
8.13.4.2.2 Adhesion should be determined by the cross cut peel test in accordance with ISO 2409 or the pull 
off test in accordance with ISO 4624, or by instruments, such as a pull-off adhesion tester, the adhesion figure 
should be in excess of 1 N/mm2. 
8.13.4.3 Surface preparation 
Good surface preparation is vital and varies depending on the condition and type of the existing finish.  
a) All surfaces deemed to be in good condition should be powerwashed to remove all dirt, debris, growths 
and erosion by-products. Grease and oil should be removed with a suitable cleaner (soap or detergent) 
and all traces of cleaner need to be removed by rinsing.   
©RSB 2023- All rights reserved                  80 
 b) All loose, flaking and delaminating coatings should be removed by either mechanical means, e.g. 
powerwash or hand preparations, or chemical means, e.g. paint stripper. Ensure all traces of chemical 
treatment are removed. Disbonding sections of PVC plastisol should be cut back to soundly adhered 
material.  
c) Rusted areas should be prepared by removal of coating, oxidation products, dirt and debris, and abraded 
or blasted to, e.g. Sa2'/2, and should be primed before re-oxidation occurs.  
d) Severely corroded panels should be replaced either wholly or sectionally, small areas can be repaired 
using a permanent filler.  
e) Prior to priming/coating, areas which have been subject to mould growths should be identified and treated 
with a biocidal wash. 
8.13.5 Expanded polystyrene 
8.13.5.1 Expanded polystyrene is used in tile or sheet form as a ceiling or wall lining and for decorative 
applications to improve thermal insulation. Wall linings are generally employed as a base for wallcoverings, 
but ceiling tiles and cornices can be painted.  
8.13.5.2 Paint solvents attack expanded polystyrene. Painting of expanded polystyrene wall and ceiling 
linings should be with water-borne paints.  
WARNING! Paints containing solvents, especially gloss finishes, can create a fire hazard when used in conjunction with expanded 
polystyrene. 
8.14 Glass and inorganic glazed surfaces 
8.14.1 General 
8.14.1.1 In addition to glass, materials in this category include glazed bricks, terracotta, faience, ceramic 
tiles and vitreous enamel. They are painted in some circumstances, e.g. to obscure clear glass or to renovate 
glazed surfaces or change their colour.  
8.14.1.2 A general characteristic of the surfaces relative to painting is that they provide little mechanical 
key, and this cannot usually be improved significantly by abrasion. Reliance has therefore to be placed on the 
inherent adhesive properties of the paint, and this can vary according to type and composition.  
8.14.1.3 The painting of extensive or prominent areas should be undertaken only after consultation with 
the manufacturer, especially if the surfaces are exposed to weather or high humidity or are subject to 
abrasion; if possible, evidence of satisfactory performance hi similar conditions should be obtained. 
8.14.2 Coating systems for glass and inorganic surfaces 
8.14.2.1 Surface preparation 
Surfaces should be perfectly clean and dry at the tune of painting. It is recommended that surfaces are 
washed with detergent solution, followed by rinsing with clean water. Where external surfaces are greasy, 
solvent cleaning may be necessary (see 7.4.1). On vitreous enamel, abrasion with waterproof adhesive paper, DRS 554: 2022 
81                ©RSB2023- All rights reserved 
 while the surfaces are wet, can help to improve adhesion. Faulting should follow cleaning as soon as the 
surfaces are dry. If there is a delay, surfaces should be wiped with a clean cloth and methylated spirits 
immediately before painting. 
8.14.2.2 Priming 
Finishes are often applied directly to glass and glazed surfaces, but the paint manufacturer's 
recommendations in this respect should be followed. Some multi-colour finishes (7/14) are applied over a 
bonding primer. Where damage or deterioration of vitreous enamel has exposed O the metal substrate, the 
exposed metal substrate should be primed. 
8.14.2.3 Finishing 
8.14.2.3.1 In the interiors of buildings, glazed bricks and ceramic tiling are the surfaces of this type most 
likely to need painting. Multi-colour finishes are used fairly widely and should be applied in accordance with 
the manufacturer's recommendations. Alkyd gloss and mid-sheen finishes and one-pack polyurethane finishes 
can also be used and should be applied directly to the surface. Chlorinated and acrylated rubber finishes 
should be considered, especially for conditions of high humidity or where condensation occurs. Some water-
borne paints can be suitable in dry conditions and are used to provide temporary shading on glass, however 
specialist coatings are available for this purpose.  
8.14.2.3.2 External surfaces should be treated as for internal surfaces but reference should be made to the 
manufacturer's instructions.  
8.14.2.3.3 None of the conventional types of paints have the durability and resistance to wear of the original 
surfaces, and, where these properties are important, consideration should be given to the use of long- life 
specialist coatings which also have good adhesion, e.g. some two-pack polyurethane and epoxy types. The 
manufacturer should be consulted regarding the choice of materials and systems. 
8.15 Bituminous surfaces and materials 
8.15.1 General 
8.15.1.1 Surfaces and materials in this category include bituminous paints and coatings, some 
preservative treatments and asphalt surfaces.  
8.15.1.2 These surfaces should not be painted with solvent-borne paints since there is a tendency for 
these surfaces to discolour them (bleeding) and sometimes to retard their drying. Cracking of applied paints 
might occur with some bituminous substrates. 
8.15.2 Bituminous paints and coatings 
8.15.2.1 Thin, hard coatings, especially when they are aged, can be primed before they are overpainted 
with solvent-borne paints using, for example, an aluminium primer (3/5). Water-borne paints should be applied 
directly without a primer or sealer (some water-borne masonry paint systems include a bituminous emulsion 
basecoat as a waterproofing membrane for porous external walls).   
©RSB 2023- All rights reserved                  82 
 8.15.2.2 Paints applied over thick bituminous coatings might crack and craze, and the cracks can 
subsequently extend into the underlying material. If removal of the bituminous coating is impracticable, it 
should be overcoated with material of similar type, e.g. tar paint or bituminous aluminium paint. 
8.15.3 Preservative treatments 
NOTE The use of creosote is prohibited, except for some industrial applications. 
Bituminous preservatives can be used for wood and some types of fibre insulating boards. Existing creosoted 
wood can generally be painted if it is has weathered for a year or more and is then primed with aluminium 
primer (3/4). A primer of this type should also be used on fibre insulating board impregnated with bituminous 
preservative, if it is to be painted with solvent-borne paint; water-borne paints can usually be applied directly to 
the board. 
8.15.4 Asphalt and bitumen 
8.15.3.1 Light-coloured finishes for asphalt and bituminous roofing materials should be used to reduce 
heat absorption and improve appearance. Particular care in the selection of coatings is essential, as 
unsuitable types can crack, as described in 8.15.2, resulting in serious damage to the roofing material. 
Because of the ponding effect that can occur on flat roofs, it is also necessary for applied coatings to have 
good resistance to moisture to prevent loss of adhesion.  
8.15.3.2 Sand-rubbing of new asphalt is recommended to avoid the formation of a bitumen rich surface. 
The sand-rubbed surface assists the adhesion of coatings but the surface should be swept to remove excess 
sand before application.  
8.15.3.3 Specialist coatings are available for use on asphalt and bituminous roofing materials, and 
reference should be made to the manufacturer for specific recommendations, based on experience.  
8.15.3.4 Quick-drying road marking paints, resistant to discoloration, should be used for marking asphalt 
roads, parking areas and factory-floors. Light-reflecting solid glass beads are incorporated in some types or 
can be applied to the surface while the paint is wet. 
9 Application and practice 
9.1 Conditions of application 
9.1.1 General 
The application and performance of coatings are affected by the conditions under which they are applied, e.g. 
of temperature, humidity and general exposure conditions. The influence of these and other factors is 
described hi 9.1.2 to 9.1.7. 
9.1.2 Temperature and humidity 
9.1.2.1 Temperature and humidity will have an effect on the drying behaviour of most coating types.  
NOTE 1 See Annex L for information on temperature and humidity.  DRS 554: 2022 
83                ©RSB2023- All rights reserved 
 9.1.2.2 The manufacturer's recommendations in respect of temperature and its relation to curing tune 
and pot life should be observed, especially in the case of specialist coatings such as two-pack epoxy and 
polyurethane coatings.  
9.1.2.3 In specifying the conditions under which coatings are to be applied, a general recommendation is 
that application should not start or should stop if the ambient temperature is below the manufacturer's 
recommendations (typically 8 °C or relative humidity exceeds 80%). In addition to the ambient temperature, a 
critical factor might be that of the surface to which the coating is applied. The temperature of heavy metal 
sections or plates, as well as plaster, rendering and masonry, for example, can be several degrees lower than 
the ambient temperature, especially early in the day.  
NOTE 2 In some circumstances, this general recommendation can be unduly restrictive and cause unnecessary delay or interruption 
of work. By agreement between the parties concerned, and having regard to the nature of the work and the types of materials involved, 
some relaxation of the recommendations in respect of temperature and relative humidity might be acceptable. Solvent-borne coatings, for 
example, can be less seriously affected than water-borne paints if applied in cold, damp conditions; application of primers and undercoats 
might be possible in conditions which preclude the application of finishes.  
9.1.2.4 Any agreed relaxation of the specified conditions should, however, be subject to the provision 
that:  
a) coatings are not be applied to surfaces on which condensation is present;  
b) coatings are of types reasonably tolerant of the prevailing conditions of application;  
c) records are kept of the occasions when relaxation is permitted. 
9.1.2.5 In assessing conditions of application, account should be taken of changes in temperature and 
relative humidity that are likely to occur within a few hours of application, and especially the effects of 
overnight frost or high humidity on recently applied coatings (see 9.1.7). 
9.1.3 Surface moisture 
9.1.3.1 Adhesion, drying and other properties are nicely to be adversely affected if coatings are applied to 
wet surfaces. Application should not proceed when, as a result of adverse weather, high humidity or other 
cause, there is a visible film of moisture on the surface.  
9.1.3.2 Condensation is often a problem in unheated buildings during the winter months. Temporary 
heating equipment can help, but it is important that heating be combined with adequate ventilation otherwise 
the problem can be aggravated. Portable gas and oil heaters produce water and should be used only if they 
are provided with means of exhausting combustion products to the outside of the building.  
9.1.3.3 In some circumstances, e.g. when painting heavy metal sections, it might be necessary to delay 
application when the temperature of the surface is below the dew point of the air because of the risk of 
condensation, even though it has not yet occurred.  
9.1.3.4 When conditions improve, wet surfaces should be dried off, and tune should then be allowed for 
contained or trapped moisture to dry out. This is especially important with absorbent surfaces but it is also 
applicable to rough metal including metal-sprayed surfaces. Prepared iron and steel surfaces that have not 
received a priming coat should be prepared further if rusting has occurred.  
©RSB 2023- All rights reserved                  84 
 9.1.4 Atmospheric pollution 
9.1.4.1 In industrial situations, fumes can retard the drying or cause discoloration of conventional 
coatings; in severe cases, it might be necessary to use modified or specialist coatings, and the manufacturer 
should be consulted.  
9.1.4.2 The adhesion and drying of coatings might be impaired by the deposition of contaminants, 
including salt in marine situations. Where this occurs, surfaces should be cleaned thoroughly before 
application of each coat, and intervals between coats should be as short as possible.  
9.1.4.3 The effects of fumes and deposition of contaminants are likely to be most severe in foggy weather 
and in conditions of high humidity. 
9.1.5 Air movement and wind 
9.1.5.1 Adequate movement of air assists drying and is essential to the removal of solvent vapours which 
can be unpleasant or potentially toxic or inflammable, especially when work is carried out in confined spaces; 
the manufacturer's recommendations in this respect should be strictly observed.  
9.1.5.2 Painting should be avoided under windy conditions unless precautions are taken, because the 
wind can carry dust and grit on to wet paint and mar its appearance.  
9.1.5.3 Precautions should be taken in the use of spray equipment externally in windy weather as paint 
droplets can be carried for considerable distances, causing damage or annoyance. 
9.1.6 Lighting 
9.1.6.1 Good lighting is essential to efficient working. Where natural daylight is lacking, an adequate level 
and type of artificial lighting should be provided.  
9.1.6.2 The lighting whilst painting should simulate, as far as practicable, the final lighting scheme in 
intensity and direction of lighting.  
9.1.6.3 For most painting operations, 500 lux should be used. Higher levels, e.g. 750 lux, should be used 
for darker colours and inspection purposes. For colour matching, limited contrast between coats or areas, and 
fine detail work, 1 000 lux might be necessary.  
9.1.6.4 Where the two higher lux levels are necessary and where colour perception in artificial light can 
be variable, illumination by lamps of colour groups 1A or IB of the CIBS Code for interior lighting [20], should 
be used; these include north light or artificial daylight types.  
NOTE Information concerning suitable illumination for differing purposes,bulbs and tubes are referred to in the CIBS Code for interior 
lighting [20]. 
9.1.7 Seasonal factors 
If exterior is undertaken hi conditions when overnight frost or condensation is likely, the application of gloss 
finishes and water-borne coatings should be tuned to allow a reasonable period for drying before nightfall, DRS 554: 2022 
85                ©RSB2023- All rights reserved 
 otherwise their appearance or film properties might be unpaired. Surfaces, which are damp as a result of 
overnight conditions, should be dried before coatings are applied (see 9.1.3).  
NOTE For further information on seasonal factors, see Annex L. 
9.2 Craft procedures and practices 
9.2.1 Condition of surfaces 
9.2.1.1 Surfaces should be in a fit condition to allow work to proceed without detriment to the coatings to 
be applied. In some circumstances additional time is needed for drying out. Work by other trades that might 
affect painting should have been completed. If some tune has elapsed since preparation of the specification, 
any change in the nature or condition of the surfaces, that might necessitate modification of the specification, 
should be drawn to the attention of the specifying authority.  
9.2.1.2 Factory-primed components should be inspected to ensure that the condition of the primer is 
satisfactory; if it is not, remedial action should be taken (refer to the relevant substrate in Clause 8). 
9.2.2 Protection and cleanliness 
9.2.2.1 Surfaces not intended to be coated, including floors, furniture and factory-finished components 
and fittings, should be protected against splashing and spilling of painters' materials or other damage. As far 
as possible, door furniture, light fittings and similar items should be removed.  
9.2.2.2 Dust and dirt should be removed before painting otherwise the appearance and performance of 
coatings can be impaired. Where a high standard of finish is required, especially with gloss finishes, a tack rag 
might be used to finish off the cleaning.  
9.2.2.3 Tools and equipment should be kept clean while in use and, where appropriate, cleaned 
immediately after use. Thorough cleaning after use is especially important with spraying equipment as 
residues of materials previously used can affect later applications or impair the efficiency of the equipment.  
9.2.2.4 Debris and waste material should be disposed of promptly and not allowed to accumulate in the 
working area. Safety precautions should be observed in the disposal of waste materials (see B.1 and B.3).  
NOTE For recommendations in respect of personal hygiene and cleanliness, see Annex B. 
9.2.3 Abrasion 
9.2.3.1 Surfaces should be abraded (rubbed down) to reduce roughness, improve paint adhesion or 
assist cleaning. The types of abrasive materials in general use are as follows.  
a) Glasspaper can be used either dry or with white spirit as a lubricant for the abrasion of wood, plaster and 
similar surfaces to improve adhesion of paint to non-ferrous metals (see 8.4.2.7). It can also be used to 
abrade painted surfaces, provided the paint is not lead-based, but wet- abrasion is more effective.  
©RSB 2023- All rights reserved                  86 
 b) Waterproof abrasive paper can be used wet or dry and is more effective than glasspaper for abrading 
painted surfaces. It should be used wet when abrading surfaces painted with lead- based paint (see 
B.I.2).  
c) Open-coated abrasive paper has the abrasive coating (typically aluminium oxide or silicon carbide) 
sparsely distributed on the paper backing to reduce clogging. It should be used in mechanical sanding 
machines.  
d) Emery cloth or paper can be used either dry or with white spirit as a lubricant in preparing metals, 
especially non-ferrous metals (see 8.4.2.7) for painting.  
e) Steel wire wool has general application for abrading and cleaning. If used in the preparation of aluminium 
for painting (see 8.4.2.3), only stainless steel wire wool should be used. Care should be taken in the 
removal of broken strands of wire wool from surfaces before painting or they can cause rust-spotting or 
discoloration. Protective gloves should be worn when using wire wool.  
f) Nylon fibre pads can be used instead of wire wool for some purposes (see 8.4.2.3).  
9.2.3.2 Abrasives should be of types and grades appropriate to their function and the nature and 
condition of the surface. Unduly coarse grades can cause unsightly scoring and scratching which shows 
through the finish. Care should be taken not to damage thin metallic coatings, e.g. thin films of aluminium on 
composite sheets. Care should also be taken to avoid damage to mouldings, arrises and similar features. If 
abrasion between coats is necessary, it should be done lightly with fine, preferably part- worn, abrasive paper 
to avoid tearing or cutting through the coating. For hand-sanding of flat surfaces, abrasive papers should be 
used in conjunction with a rubbing block.  
9.2.3.3 Dust and debris resulting from abrasion should be carefully removed and disposed of. For 
surfaces which have been dry-abraded, dusting or vacuum-cleaning should be undertaken; washing might be 
necessary. Surfaces that have been wet-abraded should be rinsed with clean water and wiped dry. On 
absorbent surfaces, tunes should be allowed for drying out before coatings are applied. 
9.2.4 Stopping and filling 
9.2.4.1 General 
Stopping and filling should be carried out as early in the coating process as the type of material used and the 
nature of the substrate allow. Most materials used for stopping and filling are absorbent and, if applied late in 
the system, e.g. immediately beneath finishing coats, can cause sinkage and variations in gloss, sheen or 
colour. It should be noted that, if overall filling of surfaces is required, this should be clearly indicated in the 
painting specification.  
NOTE 1 The materials in general use for stopping and filling are described in 7.4-4, and appropriate usage for substrates is indicated 
in Clause 8.  
NOTE 2 The term stopping or stopping-up relates to nail and screw holes, open joints, cracks and similar local cavities and deep 
depressions, while filling implies overall smoothing and levelling of shallow depressions and rough, open-textured or coarse-grained 
surfaces. DRS 554: 2022 
87                ©RSB2023- All rights reserved 
 9.2.4.2 Stopping 
9.2.4.2.1 The materials used for stopping are usually fairly stiff in consistency and are generally applied 
with a putty knife or stopping knife. The stopper should be pressed firmly into cavities in order to drive out air, 
which can prevent proper levelling. It should be knifed flush with the surrounding surface and not allowed to 
spread beyond the cavity. Deep cavities might require stopping in two stages, allowing an interval for the first 
application to harden. Nail and screw heads should be adequately countersunk for stopping, with heads 
normally not less than 2 mm below the surface.  
9.2.4.2.2 When drying-oil/resin stoppers are used, surfaces should be primed and the primer allowed to dry 
before stopping. This prevents absorption of the binder from the stopper which might cause it to shrink and fall 
out. Priming is not usually required prior to the use of water-borne and powder fillers. 
9.2.4.3 Filling 
9.2.4.3.1 Depending upon their type and consistency, fillers can be applied with a wide, flexible filling knife 
or spreader or by brush. On broad surfaces, filling knives or spreaders are generally used, brushes being 
used for mouldings.  
9.2.4.3.2 Drying-oil/resin fillers are usually applied after priming, but some can be suitable for direct 
application to unprimed surfaces; the manufacturer's recommendations in this respect should be followed. 
Water- borne and powder fillers can be applied to unprimed surfaces but, on absorbent surfaces, priming 
might be necessary to facilitate uniform spreading.  
9.2.4.3.3 Skilled application of fillers by knife or spreader should leave a surface, which requires little 
subsequent treatment, but some abrading might be necessary for final levelling. With drying-oil/resin fillers, 
waterproof abrasive paper (see 9.2.3), with water as a lubricant, can be used. Water-borne and powder fillers 
should be abraded dry. After abrading, surfaces should be rinsed or carefully dusted to remove residues of 
filler. If the surfaces have been wetted, time should be allowed for drying before painting. 
9.2.5 Preparation of materials 
9.2.5.1 Stirring 
9.2.5.1.1 Unless the manufacturer's instructions state otherwise, painting materials should be stirred before 
use and at intervals during use. The solid constituents in liquid paints can settle during storage and their re-
incorporation is essential to avoid defects such as poor opacity and retarded drying. Manual stirring is the 
method generally used for small quantities. A broad-bladed stirrer, long enough to reach the bottom of the 
container, should be used, and stirring should continue until no settlement remains. Mechanical equipment for 
stirring or shaking paint is available, and its use is advantageous when large quantities are involved.  
9.2.5.1.2 Thixotropic coatings (see 7.2) should not normally be stirred before use, except possibly for roller 
or spray application; stirring or shaking temporarily impairs the thixotropic properties.  
9.2.5.1.3 To avoid aeration and incorporation of any sediment, clear coatings are not usually stirred before 
use, but the manufacturer's instructions in this respect should be followed. Two-pack clear coatings should be 
stirred.  
©RSB 2023- All rights reserved                  88 
 9.2.5.2 Thinning 
Most of the coatings generally used in the painting of buildings, with the possible exception of some water-
borne paints, are supplied ready for application by brush or roller. Water-borne paints could be supplied ready 
for use, but some need the addition of water. Thinning of primers might be necessary to improve penetration 
or facilitate application, e.g. on surfaces of high or variable porosity. Thinning might also be necessary for 
spray application of coatings. To prohibit thinning absolutely, as some specifications require, can be 
unreasonable, but it should be carried out only under supervision and with the types of thinners and in the 
proportions recommended by the manufacturer. 
9.2.5.3 Intermixing 
Different brands or types of paints should not be intermixed without reference to the manufacturer. 
9.2.5.4 Two-pack materials 
9.2.5.4.1 Two-pack materials are supplied as two components, e.g. base and activator, hardener or curing 
agent, to be combined before use. Base and activator can be held in separate containers or in a dual- pack 
container; in either case, the components are present in the correct proportions in relation to the total quantity 
of material supplied; if a small quantity is required, it should be measured to ensure that the correct proportion 
of each component is used.  
9.2.5.4.2 Some two-pack materials require an induction period (standing time) after mixing and before they 
are ready for use. Most have a limited pot-life (i.e. length of time during which they are usable), and this is 
temperature-dependent. The manufacturer's instructions in relation to induction period and pot-life should be 
observed. 
9.2.6 Differing colours 
9.2.6.1 The manufacturer’s recommendations in respect of the colours of undercoats and first-coat 
colours should be observed. Wherever practicable, successive coats in paint systems should differ in colour. 
This assists application of continuous coats of uniform thickness, especially in conditions of poor lighting, and 
also facilitates inspection.  
9.2.6.2 Batch to batch colour variations might occur and it is therefore recommended that paint be bought 
from the same batch to ensure good colour consistency. If this is not possible, batches should be combined or 
mixed in a single container. 
9.2.7 Intervals between application of successive coats 
9.2.7.1 Generally, each coat in the system should be dry throughout its thickness before the next coat is 
applied. As indicated in 9.1, atmospheric conditions can affect the rate of drying and, in consequence, the 
interval between coats; it should not, in any case, be less than the minimum recommended by the 
manufacturer. Some coatings might be suitable for wet-on-wet application, i.e. a second coat can follow 
immediately.  
9.2.7.2 Except with coatings formulated for lengthy exposure without further coats, such as some primers 
for metal and wood (see appropriate substrate in Clause 8), intervals between coats should not normally 
exceed a few days, otherwise adhesion might be impaired. With some specialist coatings, the manufacturer 
might specify a maximum time to be allowed between coats. DRS 554: 2022 
89                ©RSB2023- All rights reserved 
 9.2.8 Inter-coat preparation 
9.2.8.1 It should be ensured that the surface is clean before application of each coat in the system. This 
is important if there has been a lengthy interval between coats especially in situations where contamination of 
the surface is likely, e.g. in marine or industrial environments.  
9.2.8.2 Except when the previous coating has become very hard, as a result of lengthy exposure, 
vigorous abrasion between coats is rarely necessary to assist inter-coat adhesion. Light scuffing with fine- 
grade, preferably part-worn, abrasive paper is sufficient to remove nibs and adherent dust particles, but care 
should be taken not to scratch or tear the coating; if this occurs or the abrasive paper rapidly clogs, it is an 
indication that the surface is not sufficiently hard to permit abrasion.  
9.2.8.3 If extensive flatting of a previous coat is necessary to assist adhesion or provide a smooth level 
surface, wet abrasion, with waterproof abrasive paper and water, is usually the most effective method, but the 
coating should be hard before it is attempted. 
9.2.9 Defective materials 
If, during the course of the work, it appears that the material might be defective, no more should be applied 
until the matter has been investigated by the manufacturer or supplier. To continue to apply material which 
might be defective can involve additional costs for which compensation could not justifiably be claimed from 
the manufacturer or supplier even if the material proves to be defective. 
9.3 Application methods 
9.3.1 General 
9.3.1.1 The principal methods of applying coatings on site are by brush, roller, paint pad and paint glove 
and spray.  
9.3.1.2 Choice of method should be determined by the nature of the work or the type of material to be 
applied. The manufacturer's recommendations regarding the suitability of coatings for application by particular 
methods should be followed.  
9.3.1.3 Whatever method is employed, operatives should be skilled and experienced in the techniques of 
application, as well as in the care and maintenance of tools and equipment and, where relevant, in the setting 
up and adjustment of equipment to obtain optimum results. 
9.3.2 Brush application 
9.3.2.1 Characteristics 
9.3.2.1.1 Brushing can be used for the application of most coatings of conventional type, especially to small 
areas or where there is much cutting-in or frequent changes of colour. It is also generally recommended for 
the application of conventional types of primers to building surfaces, on the principle that the shearing action 
of brushing forces the coating into intimate contact with the surface, although suitable types of rollers can be 
equally effective in this respect.   
©RSB 2023- All rights reserved                  90 
 9.3.2.1.2 With some exceptions, multi-colour finishes (7/15) cannot be applied by brush and should be 
sprayed. Difficulty might be experienced in the brush application of quick-drying coatings, especially to large 
areas. For these and for some specialist coatings, spray application is preferred.  
9.3.2.1.3 Brush application to large, unbroken areas is slower than roller, paint pad or spray application and 
it is more difficult to obtain a uniform coating. 
9.3.2.2 Types of brushes 
9.3.2.2.1 The construction and dimensions of brushes should conform to BS 2992. For most purposes, 
brush fillings should be pure bristle, good quality mixed bristle or synthetic filaments. Synthetic filaments are 
harder wearing than natural or animal hair and should be used when working with caustic materials such as 
cement paints, but their material-holding properties might be slightly inferior.  
NOTE Flat paint and varnish brushes, suitable for general use, range in width from 12 mm to 100 mm. Flat wall brushes, used 
mainly for application to broad surfaces such as walls and ceilings, are from 100 mm to 175 mm wide. Small fitches for narrow surfaces 
and decorative work are from 6 mm to 25 mm in width or diameter.  
9.3.2.2.2 In selecting appropriate sizes of brushes, the general principle should be to use the largest sizes 
consistent with application of a uniform coating without undue effort. Apart from any constraints imposed by 
the extent or nature of the surface to be coated, generally smaller brushes should be used with more viscous 
materials, such as solvent-borne gloss finishes, rather than with those which offer little resistance to brushing, 
such as water-borne paints.  
9.3.2.2.3 It is recommended that synthetic filament brushes are used for the application of water-borne 
coatings. They do not absorb water to the same extent as natural bristle brushes, and in consequence deliver 
a smooth, consistent application, improve the flow and wet-edge time of the coating material and hence 
reduce brush marks. Synthetic filament brushes are also much easier to clean. 
9.3.2.3 Basic techniques 
9.3.2.3.1 In general terms, the basic technique of brush application involves three phases. First, the 
material should be applied in a reasonably full coat and evenly spread, working most of it out of the brush and 
recharging as necessary. Then, without reloading the brush, it should be drawn in one direction (crossed) and 
then at right angles to this in order to distribute the coating evenly and uniformly. Finally, the coating should be 
laid off, i.e. the brush is drawn lightly in the direction of the greatest length of the work, in order to eliminate 
brush marks as far as possible.  
NOTE This technique might require modification according to the nature of the surface or the type of coating being applied.  
9.3.2.3.2 Many undercoats and most finishes have good flow properties and, for final laying off, lighter 
pressure should be used. Repeated crossing and laying off is not usually practicable with quick-drying 
coatings which should be applied as quickly as possible with the minimum of brushwork; roller or spray 
application of this type of coating is usually preferred, especially for large areas. In applying matt and mid-
sheen coatings to ceilings and walls, the material should be applied and laid off using criss-cross strokes 
(switching) rather than hi one direction.  
9.3.2.3.3 Over-heavy application of coatings should be avoided as this can cause runs and sags, 
particularly with free-flowing materials such as gloss finishes and varnishes. With some types of coatings, a 
surface skin can form which retards through drying. The opposite extreme of brushing out too far should also 
be avoided as this produces excessively thin films having poor appearance or lacking in protective properties.  DRS 554: 2022 
91                ©RSB2023- All rights reserved 
 9.3.2.3.4 Heavy accumulations of paint (fat edges) along edges and arises should be avoided by brushing 
towards them rather than in the reverse direction.  
9.3.2.3.5 Application, especially to large areas, should be so organized that wet edges are maintained, i.e. 
that each section of the work is joined up to the preceding section before its edge has set, thus preventing 
unsightly laps. On large areas, the number of painters deployed should be sufficient to permit wet edges to be 
picked up with minimum delay. Where scaffolding is necessary, its arrangement should facilitate quick transfer 
from one section of the work to the next. 
9.3.3 Roller application 
9.3.3.1 Characteristics 
9.3.3.1.1 The types of coatings described in 9.3.2 as suitable for application by brush are also suitable for 
roller application; the limitations in respect of certain types of coatings also apply. The method is quicker than 
brushing on large, unbroken areas, such as ceilings, walls, flush doors, floors and plate work but is not 
recommended for small areas or where much cutting-in is required. A brush should be used to coat internal 
angles and corners, e.g. between ceilings and walls.  
9.3.3.1.2 Although brush application of conventional types of primers to building surfaces is usually 
recommended, some types of rollers have a similar shearing action and can be equally suitable.  
9.3.3.1.3 Rollers with appropriate roller coverings should be used for the application of coatings to rough or 
uneven surfaces, such as rough-cast external walls; for this purpose, they are usually quicker and more 
effective than brushes.  
NOTE A degree of stipple or surface texture is characteristic of coatings applied by roller but, if the appropriate type of covering is 
used, this can hardly be discernible, especially with free-flowing materials such as gloss finishes. 
9.3.3.2 Types of rollers 
9.3.3.2.1 Rollers should be of good quality and robust construction. Preferably, they should have 
interchangeable roller coverings which can be selected depending on the surface or coating.  
NOTE 1 Materials for roller coverings include various natural and synthetic fabrics and fibres. Coverings employing synthetic fibres are 
widely used; they are generally described in relation to the length of the fibres, i.e. as short, medium, or long pile types, the length of the 
fibres ranging from about 6 mm to 30 mm.  
9.3.3.2.2 Short and medium pile types should generally be used for application to smooth surfaces when it 
is necessary to avoid excessive stippling of the coating. Long-pile types should be used for application to 
brickwork, rough-cast and similar surfaces or when it is necessary to impart a texture to the coating. The roller 
or paint manufacturer's recommendations regarding the most suitable types of coatings should be followed.  
NOTE 2 For general use rollers about 200 mm wide are suitable, but larger and smaller sizes can be obtained. Special rollers are 
available for the application of coatings to corrugated sheeting, pipes and curved surfaces. Many rollers, including the special types, can 
be mounted on an extension pole to extend the operative's reach.  
9.3.3.2.3 Rollers, other than the pressure feed types, should be charged by dipping the head of the roller 
into the material and then rolling it over a corrugated or coarse mesh surface to distribute the material evenly 
around the covering. Roller trays are designed for this purpose, but they hold only a small quantity of material,  
©RSB 2023- All rights reserved                  92 
 are easily overturned and are inconvenient for ladder work. Paint roller buckets should preferably be used, 
especially for large-scale work and when working from ladders; they are available in sizes holding 5 1 to 20 1 
of material.  
NOTE 3 Rollers are available in which material is supplied from a separate container' under pressure. They are claimed to show 
considerable savings in time compared with the normal type of roller by eliminating the need to recharge from a tray or bucket. In one 
type, material is supplied to the roller from an airless spray pump unit, via a flexible hose, the roller taking the place of the spray gun. 
Extension tubes giving a reach of up to about 2.5 m can befitted. 
9.3.3.3 Basic techniques 
9.3.3.3.1 Although it is probably easier to obtain a film of uniform thickness by roller than by brush, 
judgement in respect of the weight of coat applied is still essential. In particular, excessive rolling-out with a 
dry roller should be avoided. As with brush application, work should proceed systematically in sections, and 
the same attention should be paid to the maintenance of wet edges (see 9.3.2.3) although, in this respect, the 
greater speed of roller application is an advantage.  
9.3.3.3.2 Where rollers cannot reach into corners and internal angles, brushes should be used for cutting-in 
and this should be done immediately ahead of rolling, the roller then being taken as closely to the angle as 
possible.  
9.3.3.3.3 When it is required to eliminate the slight stipple that can be produced with roller application, as 
might be the case with undercoats for gloss finishes, a brush should be used for laying off immediately after 
rolling. 
9.3.4 Paint pads 
9.3.4.1 Paint pads consist of a layer of paint-holding material similar to that used for short-pile roller 
coverings (see 9.3.3.2) fixed to a rigid or flexible backing. The pad is held in a metal or plastics plate and can 
be fixed or replaceable. The plate is provided with a fixed or adjustable handle. Various shapes and sizes are 
available; the largest sizes are about 150 mm x 100 mm and can be suitable for attachment to an extension 
pole. Application by paint pad is faster than by brush but slower than by roller.  
9.3.4.2 In use, the pads should be charged by dipping the face of the covering into the paint and working 
it out on a corrugated or mesh surface as with a roller. A roller tray or roller bucket should be used for this 
purpose. The charged pad should then be placed against the surface and drawn along, using moderate 
pressure.  
9.3.4.3 Where paint pads cannot reach into corners and internal angles, brushes should be used for 
cutting-in and this should be done immediately ahead of application by paint pad, the paint pad then being 
taken as closely to the angle as possible. They can, however, produce a finish free from brush marks or 
stipple.  
9.3.4.5 Application by paint pad can be used for the following:  
a) ship-lap cladding;  
b) small areas that might not warrant putting a roller into use;  
c) panelled and flush doors;  DRS 554: 2022 
93                ©RSB2023- All rights reserved 
 d) mouldings, picture rails and skirtings;  
e) metal window frames;  
f) wide lines and stripes.  
9.3.4.5 It is essential that paint pads be of good quality and robust construction. 
9.3.5 Paint gloves 
Paint gloves or gauntlets have an outer surface of sheepskin or fabric similar to that used for roller coverings. 
In use, the gloved hand should be clipped into the material, which should then be transferred to the surface by 
wiping or dabbing. A sealed liner protects the hand, wrist and forearm against soiling with paint. They can be 
used to coat pipes, railings and surfaces which are inaccessible to other methods. 
9.3.6 Spray application 
9.3.6.1 General 
9.3.6.1.1 There are several types of spray equipment, differing in method of operation and in the coatings 
and types of work for which they are suitable. In general, however, it can be assumed that there is spray 
equipment available for the application of virtually every type of coating likely to be used for buildings and 
structures. 
9.3.6.1.2 Spraying can be used on large, unbroken areas where the nature of the work permits continuous 
working for lengthy periods enabling a speed of application which is faster than other methods of application. 
Spraying should not be used on small-scale work unless the coatings are of a type for which spray application 
is essential or preferred; brush or roller application can be more economic. 
9.3.6.1.3 Spray application is essential for most multi-colour finishes (7/14) and is preferred for coatings 
based on solution binders (e.g. 11/5), especially for application to large areas. Zinc-rich epoxy primers (4/7) 
should be applied by spray, as should some specialist coatings. The manufacturer's recommendations 
regarding the preferred method of application should be followed.  
9.3.6.1.4 The following possible limitations to spray application should be taken into account.  
a) The need for extensive masking or protection of surfaces not to be coated, although this is influenced by 
the type of equipment used.  
b) Possible hazards to health or safety (see Annex B).  
c) Spray application on exterior work in windy weather can cause difficulties as spray mist can be carried 
considerable distances and cause damage or nuisance. As in relation to a), the type of equipment used is 
a relevant factor.  
d) It is generally recommended that conventional primers for building surfaces not be applied by spray. 
Exceptions to this include zinc-rich epoxy primers and some specialist types which might be unsuitable for 
application by brush or roller.   
©RSB 2023- All rights reserved                  94 
 9.3.6.1.5 Coatings and spray equipment manufacturer's recommendations on the selection and setting up 
of equipment and the preparation of materials should be followed and their guidance sought in cases of doubt. 
9.3.6.2 Types of spray equipment 
9.3.6.2.1 General 
9.3.6.2.1.1 The following types of spray equipment are in general use for the site application of coatings:  
a) air spray;  
b) airless spray;  
c) air-assisted airless spray.  
9.3.6.2.1.2 Modified forms of spray equipment include hot spray and electrostatic spray equipment, but 
these are not used to a significant extent for site work. 
9.3.6.2.2 Air spray 
9.3.6.2.2.1 In air spray equipment, air under pressure is employed to atomize the coating and convey it to 
the surface. According to the design of the equipment, working air pressures range typically from about 0.20 
MPa to 0.47 MPa (30 lbf/in2 to 70 lbf/in2) or more.  
9.3.6.2.2.2 Lightweight units operating at pressures of 0.20 MPa to 0.27 MPa (30 lbf/in2 to 40 lbf/in2) 
should be used for decorative coatings. Larger units operating at higher pressures can be used for most types 
of coatings although airless spray application (see 9.3.6.2.3) might be preferred for some specialist types. 
Atomization is more effective with larger units than with lightweight units, enabling a higher standard of finish 
to be achieved. In addition, material throughput is higher, facilitating more rapid application.  
9.3.6.2.2.3 As all forms of air spraying give rise to spray mist (although this is less pronounced with 
equipment operating at lower pressures) surfaces that are not to be painted should be masked and, for interior 
working, the provision of additional ventilation or means of extracting spray mist from the working area might 
be necessary.  
9.3.6.2.2.4 If compressor units for air spray equipment are powered by a petrol or diesel engine, they 
should be located outside the building, if possible; if this is not practicable, exhaust fumes should be conveyed 
directly to the open air. 
9.3.6.2.3 Airless spray 
9.3.6.2.3.1 In airless spray equipment, a fluid pump forces the material at very high pressure, typically 
14.3 Pa to 21.4 Pa (2 000 lbf/in2 to 3 000 lbf/in2), through a restricted orifice in the spray gun so that on 
release to the atmosphere the material immediately atomizes. Airless spray equipment is available in a wide 
range of sizes and capacities, including small units weighing less than 45 kg (100 Ib).  
9.3.6.2.3.2 High rates of application can be achieved with airless spray equipment, and the absence of 
atomizing air means that there is almost no spray mist and consequently little waste of material or necessity 
for extensive masking. Most types of coatings can be applied, possible exceptions being those containing DRS 554: 2022 
95                ©RSB2023- All rights reserved 
 coarse aggregates or fibres, e.g. some masonry paints. Thicker films can be obtained than with air spray 
equipment, and should be used in particular for the application of high-build specialist coatings.  
9.3.6.2.3.3 With some types of airless spray equipment, a separate source of compressed air is required 
to operate the fluid pump. When this is supplied by a compressor powered by a petrol or diesel engine, 
precautions in respect of exhaust fumes as described hi 9.3.6.2.2 should be taken.  
9.3.6.2.3.4 Because of the very high pressures involved, caution should be exercised in the handling of 
airless spray equipment; in particular, the spray gun should never be pointed towards any part of the body 
while the equipment is in operation. 
9.3.6.2.4 Air-assisted airless spray 
Air-assisted airless spray equipment combines some of the characteristics of high-pressure air and airless 
spray methods. A pump unit of similar type to that used for airless spray is employed, but it operates at lower 
pressure, usually in the range 6.7 MPa to 12.0 MPa (900 lbf/in2 to 1 700 lbf/in2). In addition, the spray gun is 
supplied with a small volume of air at low pressure. Air-assisted airless spray equipment allows the operator 
the same degree of control over application as does air spraying while having the freedom from spray mist 
and economy in the use of coating associated with airless spray 
9.3.6.2.5 Hot spray 
In hot spray equipment, the material is passed through a heater unit before delivery to the spray gun. Heating 
enables high viscosity, low solvent (or solvent-free) coatings to be applied by spray to give a thicker film. 
Coatings need to be specially formulated for hot spray application; water-borne coatings should not be used.  
The hot spray method can be used in conjunction with either air spray or airless spray equipment. 
9.3.6.2.5.1 Electrostatic spray 
Electrostatic spray method involves imparting to the material an electrical charge of opposite potential to that 
of the surface to be coated, causing the charged particles to be attracted to the surface. This reduces wastage 
of material and also creates a wrap round effect so that components such as pipes and railings can be coated 
all round from one direction. Using a special unit to impart a charge to the material, the method can, in 
principle, be used in conjunction with air spray or air-assisted airless spray equipment for the application of 
coatings to structural surfaces. However, the electrical characteristics of the material and the surface to which 
it is applied are critical factors and, in practice, electrostatic spraying has little application for site work 
although it is used widely in industrial finishing. If its use is considered, equipment and coatings manufacturers 
should be consulted. 
9.3.6.3 Basic techniques 
9.3.6.3.1 All masking and protection of adjacent surfaces should be completed before spraying starts. 
Elaborate masking might be unnecessary when airless spray equipment is used; because of the virtual 
absence of spray mist or over spray, it is often possible to cut-in by using a hand-held shield. If masking tape 
is used in spraying, it should be removed as soon as possible after completion of the work. It is advisable to 
cut along the edges of the tape with a sharp knife to prevent the coating film being pulled away with the tape.  
WARNING! Because of the very high pressures involved, caution should be exercised in the handling of spray equipment; in particular, 
the spray gun should never be pointed towards any part of the body while the equipment is in operation.   
©RSB 2023- All rights reserved                  96 
 9.3.6.3.2 Equipment should be checked to ensure that it is in good condition and working efficiently. Spray 
guns should be of appropriate type and set up in relation to the material to be applied; reference should be 
made to the equipment or coating manufacturer's literature for guidance in this respect.  
9.3.6.3.3 Coatings should be prepared for use as described in 9.2.5. It should not be assumed that 
coatings for spray application necessarily need to be thinned. Unless the manufacturer's recommendations 
are to the contrary, or experience suggests otherwise, a trial application of unthinned coating should first be 
made. If thinning is necessary it should not exceed the manufacturer's recommendations; if excessive 
amounts of thinner are required to facilitate application, it is likely that the equipment is of unsuitable type or is 
not operating correctly.  
9.3.6.3.4 When spraying, the gun should be held at right angles to the surface, horizontally and vertically. 
In air spraying, the distance between the front of the gun and the surface should be 150 mm to 200 mm; in 
airless spraying, the distance should be 300 mm to 375 mm. These distances should be maintained as the 
gun is moved across the surface; i.e. it should not be swung or arced. Each stroke should be made at a 
constant rate to maintain a uniform thickness of coating. The trigger of the spray gun should be pressed just 
before the start of each stroke and released just before it is completed. With air spray guns, the trigger 
movement should be gentle and progressive, but with airless spray guns it should be firm and abrupt. Each 
stroke should overlap the previous one to ensure uniform coverage; usually, more overlap is required with air 
spraying than with airless spraying. 
10 Inspection, sampling and testing 
10.1 General 
Most painting work is subject to final inspection on completion; on major projects, the work should be subject 
to inspection (see 10.2) at all stages. Sampling and testing of materials (see 10.3) might be required. 
10.2 Inspection 
10.2.1 General 
10.2.1.1 Inspection should be carried out to ensure compliance with the specification. It should not be 
considered as a substitute for proper supervision of the work by the contractor nor a means of compensating 
for an inadequate or incorrect specification.  
10.2.1.2 Inspection should also be carried out to ensure that acceptable standards of workmanship and 
quality of finish are achieved. It is often difficult to specify these in terms which preclude subjective judgement. 
Where possible, reference standards on representative areas should be used to serve as a basis for tendering 
and inspection, but it is important to ensure that the standards set are realistic in relation to the system 
specified, the nature of the substrates and the conditions under which the work is to be done.  
10.2.1.3 The responsibility for inspection should be independent from that for application.  
NOTE On large projects, the employment of a specialist inspection organization might be justified; in other cases, inspection might 
be carried out by members of the specifying authority's staffer a clerk of works.  
10.2.1.4 Inspectors should have a good knowledge of the materials, processes and techniques employed 
in the painting of buildings. DRS 554: 2022 
97                ©RSB2023- All rights reserved 
 10.2.1.5 When work is to be subject to inspection, the intended procedure should be described in the 
specification. It is important to ensure that resources are available to implement the procedure described, 
especially when the work is to be subject to inspection and approval at each stage (see 10.2.2 regarding 
levels of inspection). If the inspector is empowered to suspend work (or take comparable action) or take 
samples, this should also be stated in the specification. 
10.2.2 Levels of inspection 
10.2.2.1 Typical levels of inspection should be as follows: 
a) Full – All operations are subject to inspection and approval before the next stage is started. This is the 
most effective level of inspection but is likely to require the services of one or more full-time inspectors 
and might be justified only on very large or complex projects.  
b) Intermittent – Partof all operations is inspected and approved before the next stage is started. This level of 
inspection is less effective than full inspection but is less demanding in terms of cost and resources and 
therefore more appropriate for smaller projects or work of a straightforward nature.  
c) Occasional – Alloperations are subject to inspection initially to establish standards of workmanship. 
Thereafter, inspection is carried out as judged necessary by the inspector. The effectiveness of this level 
of inspection depends largely upon the quality of supervision exercised by the contractor. 
10.2.2.2 The following factors should be taken into account when selecting the level of inspection 
appropriate to a painting operation:  
1) the nature of the work and the functions of the coating system: for example, normal maintenance 
redecoration work might not require full inspection, but this might be necessary for work involving the 
application of specialist coatings;  
2) the cost of inspection in relation to the value of the contract;  
3) the resources available for inspection, especially when several locations are involved;  
4) the quality of supervision likely to be exercised by the contractor.  
10.2.2.3 Ad hoc inspection of work in progress might be all that circumstances or resources permit. 
Although better than no inspection, it cannot be regarded as an effective method of ensuring compliance with 
the specification.  
10.2.2.4 In some circumstances, e.g. when work is of short duration, it might not be possible to do more 
than inspect the work on completion. This might suffice where finished appearance is the main criterion, but it 
does little to establish that the work specified has actually been carried out and, in particular, that the surfaces 
have been correctly prepared. 
10.2.3 Duties of the inspector 
The inspector should assess whether compliance with the specification has been achieved in all respects. The 
inspector's duties are not described here in detail but should include some or all of the following:   
©RSB 2023- All rights reserved                  98 
 a) ensuring that surfaces are in fit condition for the application of coatings: this might include checking the 
moisture content of substrates;  
b) ensuring that preparatory work is carried out as specified and, where applicable, to agreed standards;  
c) ensuring that work is carried out under suitable conditions, e.g. of weather, temperature, humidity, 
ventilation and illumination;  
d) ensuring that materials are of the types and makes specified and are properly stored;  
e) ensuring that the specified number and sequence of coats are applied, and that application is in 
accordance with the specification or the manufacturer's recommendations: this might include checking film 
thickness;  
f) if so empowered, suspending work or taking comparable action when there are reasonable grounds for 
doing so, e.g. if conditions are unfavourable for painting: work should be stopped if it appears that 
materials might be faulty (see 9.2.9);  
g) taking samples for testing if this is a requirement of the specification or is necessary in order to investigate 
apparent defects;  
h) drawing the attention of the client or specifier to any modifications to the specification which might appear 
necessary in order to achieve a satisfactory result;  
i) maintaining work records and preparing progress reports;  
j) where a separate painting schedule is provided, ensuring that all items are finished in the required colours 
and types of finish. 
10.2.4 Final inspection 
Whether or not work has been subject to stage inspection, it should be inspected on completion. In some 
circumstances, as noted in 10.2.2, this might be the only inspection carried out. Final inspection should be 
made in the presence of the contractor or the contractor's representative. Arrangements should be made to 
inspect work which will subsequently be inaccessible before removal of scaffolding. The main points on which 
the general quality of coating systems should be judged by visual inspection are as follows:  
a) where applicable, satisfactory stopping and filling: it should be clearly specified if overall filling of surfaces 
to achieve a high standard of finish is required;  
b) uniformity of gloss, sheen or texture;  
c) with pigmented finishes, uniformity of colour and satisfactory hiding of the substrate or previous colour;  
d) freedom from conspicuous film defects such as runs, sags, wrinkling or fat edges; entrapped dust, dirt or 
paint skins; bare or starved areas; prominent brushmarks, roller stipple or spray mottle;  
e) freedom from tackiness;  DRS 554: 2022 
99                ©RSB2023- All rights reserved 
 f) accuracy of cutting-in;  
g) general cleanliness, with no soiling or disfigurement of adjacent surfaces.  
In assessing the general quality of work, the significance of any observed defect should be considered in 
relation to the functions of the coating system. For example, defects that affect appearance might not be 
important where protection is the sole or essential function. Allowance should also be made for the influence 
of conditions or circumstances outside the control of the contractor, such as the condition of the substrate, 
which might be highlighted by low angle illumination (see also 9.1.6). 
10.3 Sampling and testing 
10.3.1 The routine sampling and testing of materials should be carried out if required for one or both of the 
following reasons:  
a) to ensure compliance by suppliers with specifications or stated requirements for materials;  
b) as a safeguard against over-thinning, adulteration or similar undesirable practices during application.  
10.3.2 In either case, samples should be taken or set aside for examination by the specifying authority.  
10.3.3 For the reason indicated in a), samples should be in the original unopened containers. In respect of 
b), samples should be taken during application, e.g. from painters' kettles or spray-equipment containers. At 
least two samples should be taken, one for testing and one for the contractor; it might be advisable to take a 
third sample for submission to the manufacturer should this subsequently prove to be necessary.  
10.3.4 Subsequent testing is generally the responsibility of the specifying authority, but the specification 
should define the contractor's responsibility for providing samples (including the frequency and quantity of 
material to be provided) and describe to which standard the tests should be carried out.  
10.3.5 The coating should be tested in comparison to a test sample against an agreed standard. This might 
be the manufacturer's specification for the material or a physical sample supplied by the manufacturer or 
taken from a previously unopened container after thorough mixing. If they are available, the batch numbers of 
materials used as standards or submitted for testing should be recorded.  
10.3.6 The paint should be tested in accordance with the relevant part of ISO 2431. ISO 2431 describes a 
comprehensive range of tests for paint under the following general headings:  
Group A: Tests on liquid paints (excluding chemical tests)  
Group B: Tests involving chemical examination of liquid paints and dried paint films  
Group C: Tests associated with paint film formation  
Group D: Optical tests on paint films  
Group E: Mechanical tests on paint films   
©RSB 2023- All rights reserved                  100 
 Group F: Durability tests on paint films  
Group G Environmental tests on paint films (including tests for resistance to biological growth, corrosion and 
chemicals)  
Group H Paint and varnish defects  
10.3.7 Most of these tests require laboratory facilities and should be carried out by trained personnel.  
10.3.8 Where the measurement of flow time is tested in accordance with ISO 2431, a minimum of 100 ml of 
material should be taken for testing. Where the thickness of applied paint films is to be measured, it should be 
in accordance with ISO 2431.  
NOTE For further guidance on protective coatings on structural steel, see BS EN ISO 12944, and for concrete, see BS EN 1504-
10. 
11 Maintenance 
11.1 General 
11.1.1 The recommendations given in ISO 12944 and ISO 14713-1 should be followed for the maintenance 
painting of steel structures and those in ISO 16311 (Parts 1-4) for concrete structures.  
NOTE 1 Recommendations on the maintenance painting of buildings can be found in 5.10.  
11.1.2 The general aim of maintenance in relation to coating systems should be to maintain or restore to a 
satisfactory standard the effectiveness of coating systems to their original functions (can include cleaning) at 
the lowest cost assessed on an annual basis. 
NOTE 2 Attention is drawn to statutory requirements or terms of occupancy which require that maintenance is carried out.  
11.1.3 Maintenance requirements should be considered at the design stage of new buildings.  
NOTE 3 Application of the design principles referred to in Clause 4, including those relating to access, can make a considerable 
contribution to ease and economy of maintenance.  
11.1.4 Initial treatment of new substrates, as described in Clause 8, should be considered in relation to 
subsequent maintenance requirements. Except possibly where the condition of substrates imposes 
restrictions on the selection of coating systems, as can be the case with wet substrates, the aim should be to 
use systems, which provide a sound base for further coats with the minimum of preparation.  
NOTE 4 Initial preparatory treatment is especially important as it can affect the performance of coating systems throughout the life of 
the building. Some effective preparatory treatments, e.g. abrasive blasting of steelwork or preservative treatment of timber, can be difficult 
or impossible to carry out as maintenance operations.  
11.1.5 A planned approach should be adopted in order to achieve the aims of maintenance. An essential 
factor is the establishment of a maintenance schedule, for areas requiring regular treatment at intervals that 
experience and observation have shown to be the most economic and best suited to local conditions and 
specifications.  DRS 554: 2022 
101                ©RSB2023- All rights reserved 
 11.1.6 The maintenance schedule should include provision for regular inspection and recording of the 
condition of coating systems so that their performance can be monitored and evaluated. This facilitates proper 
assessment of future requirements and enables adjustments to be made to the maintenance schedule, if this 
is found to be necessary. 
11.1.7 Records should also be kept of the details, including costs, of all maintenance treatments carried out. 
11.2 Factors affecting decisions on maintenance 
11.2.1 Timing and frequency 
11.2.1.1 In principle, maintenance should be carried out while the existing coating is in sound condition, 
when little more than cleaning down and the application of the minimum number of coats needed to restore 
the original properties is necessary.  
NOTE 1 In practice, the condition after a given period of exposure is unlikely to be uniform over all parts of a building. Typically, 
some parts will still be in good condition when others require treatment; overall treatment at this stage might well be uneconomic. On the 
other hand, if deterioration is allowed to proceed too far, it is likely that extensive preparation and possibly complete renewal of the 
system over large areas will be necessary. The additional cost of the work might then exceed any apparent saving made by delaying 
maintenance. Hidden costs might be incurred as a result of deterioration of structural materials, loss of production or revenue decline in 
amenity value and other factors.  
11.2.1.2 Buildings should be regularly inspected and the findings recorded to determine the optimum 
frequency of maintenance. Where experience or records are lacking, as they can be with new buildings, 
maintenance inspections should be carried out at relatively short intervals in the early stages.  
NOTE 2 If this can be implemented, a film of substantial thickness can be built up fairly quickly, an important factor where the system 
has a protective function. 
11.2.2 Condition of paintwork 
11.2.2.1 The form and extent of any deterioration that has occurred influences the nature of the 
preparatory work necessary and, in many instances, the selection of coating types and systems (see 11.2.4). 
Its significance should be assessed in relation to the functional requirements.  
NOTE For example, where the emphasis is on protection, forms of deterioration, which affect appearance alone, such as soiling, 
colour change or reduction in gloss, might have little significance. Conversely, most forms of deterioration affect appearance although 
they might not impair protective properties.  
11.2.2.2 Causes of deterioration should be investigated, unless they are obvious, so that corrective action 
can be taken (see 11.3). 
11.2.2.3 The more commonly encountered defects, typical causes and considerations in respect of 
remedial treatment can be found in Table 19 and Table 20, but where unusual or rapid deterioration is 
apparent, expert investigation and advice should be sought.  
©RSB 2023- All rights reserved                  102 
 11.2.3 Variability of deterioration 
Deterioration varies according to aspect, elevation, local exposure conditions, conditions of service and other 
factors and so specifications should be modified to allow for different forms of preparations or the application 
of additional coats. In some circumstances, patch-painting (see 11.2.7) should be considered. 
11.2.4 Structural features 
11.2.4.1 Where it is evident that structural or design features have contributed to the deterioration of 
coatings, they should be modified if practicable and economically justifiable and such modifications may 
include the following.  
a) improving drainage or run-off to avoid retention of water on horizontal surfaces;  
b) preventing discharge of steam, water or industrial fumes on to coated surfaces;  
c) measures to prevent or reduce condensation on internal surfaces (see 4.6.4.3);  
d) sealing gaps, e.g. between wood frames and adjacent masonry;  
e) providing drip mouldings or canopies over external doors and windows if they are exposed to rainwater 
run-off;  
f) providing guard rails to prevent damage to painted walls in heavy traffic areas, e.g. corridors in factories 
and hospitals;  
g) enclosing plant and equipment to prevent splashing or spillage.  
11.2.4.2 Where painted surfaces are subject to very heavy wear or other forms of attack, alternative 
materials should be used, e.g. ceramic tiles or plastics sheets or components. 
11.2.5 Atmospheric pollution 
Painted surfaces subjected to heavy soiling and/or pollution from road traffic should be cleaned regularly (see 
11.5.3) and might require more frequent painting. 
11.2.6 Building function 
11.2.6.1 The function of a building or the type of occupancy should be established in order to determine 
the rate of deterioration of coatings, the type systems used and the frequency of maintenance.  
NOTE The function of a building might also affect its availability for maintenance treatment. For example, maintenance might be 
possible only outside normal working hours and then only for limited periods, and this can affect costs or impose constraints on the 
selection of coating systems. Similar considerations might apply when maintenance can be carried out only during shut-down periods.  
11.2.6.2 Building function and occupancy is likely to change and consideration should be given to the 
effect on maintenance requirement since the last or initial treatment. DRS 554: 2022 
103                ©RSB2023- All rights reserved 
 11.2.7 Patch-painting 
11.2.7.1 Where there are marked differences in the condition of paintwork on different parts of a building, 
patch-painting should be considered.  
NOTE Patch-painting, as a form of interim treatment, is generally more applicable to situations where protection is the major factor, 
e.g. on steel structures, and might not be acceptable where appearance is important. 
11.2.7.2 Where the area to be treated is easily accessible, patch-painting should be carried out. However, 
if a significant amount of scaffolding is needed, thereby making the cost of access a high proportion of the 
overall treatment cost, it might be more economical to recoat the whole structure. 
11.3 Selection of coating systems for maintenance 
11.3.1 General 
11.3.1.1 Where the coatings used previously have performed satisfactorily, materials of similar type should 
be used for maintenance.  
11.3.1.2 Where performance has not been satisfactory, the reasons for this should be established which 
may include one or more of the following:  
a) application to new wet substrates, e.g. plaster, concrete, brickwork and similar materials;  
b) inadequate or incorrect preparation of surfaces;  
c) low film thickness in protective coating systems;  
d) adverse conditions, e.g. of temperature or humidity, during application;  
e) unskilled application;  
f) use of poor quality materials;  
g) use of materials of unsuitable type.  
NOTE The type of coating used might have proved unsuitable either because the original requirements were not correctly 
appraised or because of subsequent changes in the exposure conditions, conditions of service or functions.  
11.3.1.3 Where a) is the cause of unsatisfactory performance, this does not necessarily imply a need to 
use a different type of material, provided drying out is complete and the surface is correctly prepared.  
11.3.1.4 However, where a permeable type of coating was used for initial treatment, functional 
requirements might indicate a change to a coating more resistant to washing or wear.  
11.3.1.5 Where faulty performance is attributable to b), c), d), e) or f), corrective action should be taken in 
respect of procedures or quality of material rather than a change in the type of coating.   
©RSB 2023- All rights reserved                  104 
 11.3.1.6 Where g) is the cause of unsatisfactory performance, the principles described in 4.6 should be 
followed in selecting alternative coating systems and reference should be made to 4.6.4 for coating systems 
with special conditions and requirements. 
11.3.2 Compatibility of coatings 
11.3.2.1 Generally, no problems will be encountered in applying successive coatings of similar type. 
Difficulties might, however, be experienced with some combinations of existing and new coatings of dissimilar 
type. The manufacturer's advice should be sought if there are doubts as to compatibility of old and new 
coatings, but the following are typical of circumstances that might require consideration.  
a) Application of water-borne coatings. Adhesion of these coatings, e.g. water-borne paints, over solvent-
borne coatings might be poor, especially in conditions of high humidity and to glossy surfaces, which have 
to be abraded (see 11.5.4).  
b) Application of solvent-borne coatings over water-borne coatings. This does not usually present a problem 
if the existing coating is sound and firmly adhering, but a primer-sealer (5/3) might be required on highly 
pigmented or absorbent coatings.  
c) Application of specialist coatings, e.g. two-pack epoxy or polyurethane types, over drying- oil/resin 
coatings. This might be possible if the existing coating is sound, hard and aged, but there is a risk that 
softening, cracking or lifting will occur. The manufacturer's advice should be sought in cases of doubt, and 
small-scale trials might be necessary.  
d) Application of drying-oil/resin coatings over zinc-rich primers. Advice should be sought when drying-
oil/resin coatings are to be used over zinc-rich primers.  
e) Application of all types of coatings over bituminous coatings (see 8.15 and 11.5.9.2).  
11.3.2.2 Difficulty can sometimes be experienced in identifying existing coatings Q by type especially in 
older buildings although in most cases this is not ^ significant in relation to the selection of coatings for 
maintenance.  
11.3.2.3 Where identification is necessary, either simple site tests, e.g. the reaction of the coating to 
solvents of various types, or in other cases, laboratory examination should be undertaken to provide the 
information. 
11.3.3 Components of maintenance coating systems 
11.3.3.1 If the existing coating is generally in sound condition and materials of similar type and colour are 
to be used for repainting, either one undercoat and one coat of finish, or two coats of finish, as appropriate, 
will usually provide a satisfactory result. Allowance should be made for bringing forward (see 11.5.7) localized 
areas from which the old paint has been removed.  
11.3.3.2 Additional coats might be required if a pronounced colour change is to be made, especially if the 
change is from a dark colour to white or a light colour. Additional coats might also be necessary with some 
bright or strong colours; reference should be made to manufacturer's literature for guidance.  DRS 554: 2022 
105                ©RSB2023- All rights reserved 
 11.3.3.3 Exceptionally, e.g. on internal work in good condition and where the same or a similar colour is to 
be used, one coat of some types of finish might suffice, but manufacturer's recommendations hi this respect 
should be followed.  
11.3.3.4 Surfaces from which the old coating has been removed completely should receive a full system 
as described for new substrates in Clause 8. 
11.4 Organization of maintenance work 
11.4.1 Reference should be made to Clause 5 for general guidance on organization and Clause 9 for general 
guidance on conditions of application and procedures. The following factors which have particular relevance to 
maintenance work should also be taken into account:  
a) Restricted access, e.g. a requirement that the work be done only at night or weekends. This might impose 
constraints on the nature or standard of preparatory work or the types of coatings that can be used. It is 
also likely to increase costs.  
b) It might be necessary to isolate the working area, e.g. by the erection of temporary screens or partitions, 
to limit interference with the normal functions of the building. Similar precautions might be required in 
order to create a satisfactory working environment, e.g. to exclude process fumes or dust from the 
working area during application of coatings.  
c) In some circumstances, e.g. in food factories, precautions might have to be taken to prevent 
contamination of products by solvent vapours or other constituents of coatings. Isolation of the working 
area, as in b), might be sufficient, but there might also be constraints on the types of coatings that can be 
used. Specific requirements should be established and the measures to be taken agreed between client 
and contractor.  
11.4.2 Reference should be made in specifications to these and any other special requirements or conditions 
which might affect the organization of maintenance work. 
11.5 Preparation of painted surfaces 
11.5.1 General 
11.5.1.1 The preparation of painted and similarly treated surfaces should involve one or more of the 
following processes:  
a) removal of coatings (see 11.5.2);  
b) cleaning (see 11.5.3);  
c) abrasion (see 11.5.4);  
d) priming (see 11.5.5);  
e) stopping and filling (see 11.5.6);   
©RSB 2023- All rights reserved                  106 
 f) bringing forward (see 11.5.7);  
g) treatment of biological growths (see 11.5.8);  
h) treatment of stains and discoloration (see 11.5.9).  
NOTE On the assumption that preparatory work will be carried out by skilled and experienced operatives, techniques and methods 
are not described in detail.  
11.5.1.2 For information on the preparation of old unpainted surfaces, e.g. exterior masonry and non-
ferrous metal, reference should be made to the relevant substrate in Clause 8. 
11.5.2 Removal of coatings 
11.5.2.1 General 
11.5.2.1.1 Whether or not a coating is to be removed will depend upon its condition and its compatibility with 
the coating to be applied.  
11.5.2.1.2 If the existing coating is in sound condition and one of similar or compatible type is to be applied, 
removal is unnecessary. A significant difference in colour between the existing paint and that to be applied 
does not usually justify its removal.  
11.5.2.1.3 Complete or partial removal of coatings should be undertaken where there is general poor 
adhesion, flaking, peeling, blistering, cracking, crazing and severe chalking or powdering of the coating. 
Rough (e.g. heavily brush-marked) or textured coatings, although generally sound, should be removed for 
maintenance purposes, where their smoothing or levelling would be impracticable or more costly than 
removal.  
11.5.2.1.4 Where the coating to be applied is not compatible with the existing one, e.g. if a specialist coating 
containing strong solvents is to be applied over a coating of conventional type, the coating should be 
removed. General guidance on the compatibility of coatings is given in 7.3.5, but the manufacturer's guidance 
should be sought in case of doubt.  
11.5.2.1.5 Where the general condition of a coating is obviously poor, it should be removed.  
NOTE Frequently, however, and especially in older buildings, the extent to which removal is necessary might not become apparent 
until work has started; for example, what might have appeared to be isolated flaking might prove to be indicative of poor adhesion overall.  
11.5.2.1.6 When there is doubt about the extent to which coatings should be removed, the specification 
should include a contingency allowance for the removal of coatings from a stated percentage of the areas 
affected and for the subsequent measurement of the area of the coatings actually removed. 
11.5.2.2 Removal by heating 
WARNING! Removal of paint by heating can result in the emission of toxic fumes and should not be used for the removal of paints 
containing lead pigment. DRS 554: 2022 
107                ©RSB2023- All rights reserved 
 11.5.2.2.1 Burning off 
11.5.2.2.1.1 Burning off with a blowtorch is usually the quickest and most economical for some types of 
coating, such as conventional oil or alkyd paints. It is not effective on all coatings and a test should be carried 
out on a small area before proceeding.  
11.5.2.2.1.2 It should not be used to remove highly flammable coatings, e.g. cellulose types, or in 
proximity to flammable materials.  
11.5.2.2.1.3 Burning off should not be used for removing coatings from woodwork that is to be recoated 
with a clear or semi-transparent coating system, because the wood might be scorched or discoloured. Burning 
off should not be used for carved or heavily moulded woodwork as it is generally impracticable.  
11.5.2.2.1.4 Plaster, cement rendering, asbestos-cement and similar substrates should not be burned off 
unless the coating is of sufficient thickness to soften without transmitting excessive heat to the surface, 
otherwise cracking or disintegration, which might become explosive, can occur. Even then, only a low flame 
should be used.  
11.5.2.2.1.5 Burning off should not be used for metal, as heat is conducted away too rapidly for burning off 
with the normal type of blowtorch to be effective. Flame cleaning (see 8.3.4.2.3) can be used to remove most 
paint coatings from steelwork, but this is not usually the essential reason for its use.  
11.5.2.2.1.6 During burning off, all flammable materials, e.g. curtains and hangings, should be removed 
from the working area. Great care should be taken about burning off in situations where the flame might 
penetrate gaps and ignite accumulated rubbish such as old birds' nests. Means of extinguishing fire should be 
readily available. Burning off should be completed well before operatives leave the work area. Burned off 
surfaces and surroundings should be carefully inspected before leaving the work area to ensure that there are 
no signs of combustion (e.g. smouldering and high surface temperatures). 
11.5.2.2.2 Hot air 
Paint coatings can be softened by heat generated by passing a stream of air through an electrically operated 
heating element. Although the temperature of the air (up to 600 °C) is lower than that of a gas blowtorch 
(approximately 1 900 °C), it is sufficient to soften and permit the removal of oil-paint coatings. Although the 
absence of a flame decreases the fire hazard and the risk of damage to the surface, great care should still be 
taken. 
11.5.2.3 Paint removers 
11.5.2.3.1 Paint removers should be used to remove coatings when the nature of the substrate or other 
considerations precludes removal by heating as described in 11.5.2.2. There are two main types of paint 
remover: alkaline (or caustic) and organic solvent.  
11.5.2.3.2 Alkaline paint removers, based on caustic soda, potash or similar material, are low in cost, non- 
flammable and water-rinsable. They readily saponify drying-oil/resin coatings but are usually ineffective with 
other types. They attack aluminium and zinc, and their residues are difficult to remove especially from porous 
surfaces.  
11.5.2.3.3 Solvent-type paint removers can be based on flammable or non-flammable solvents. Solvent-type 
paint removers as specified in RS EAS 929 are based on dichloromethane and are non-flammable and water- 
©RSB 2023- All rights reserved                  108 
 rinsable and should be used for removing solvent-borne coatings. For other types of coatings including water-
borne paints and two-pack coatings, solvent-type paint removers of similar type, but not necessarily 
conforming to RS EAS 929, may be used.  
11.5.2.3.4 Paint removers should be applied liberally and left until the coating has softened sufficiently to 
enable it to be removed easily. Thick films can require several applications. When removal is complete, the 
surface should be cleaned in accordance with the manufacturer's instructions. With alkaline types, vinegar or 
acetic acid can be added to the rinsing water to neutralize residues.  
11.5.2.3.5 In using paint removers, lungs should be protected with a respirator, skin contact should be 
avoided, and the eyes and hands should be protected. Solvent-borne types should be used in conditions of 
good ventilation (see also B.1.4, B.2 and B.3).  
11.5.2.3.6 Particular care should be taken with industrial or phenolic paint removers. 
11.5.2.4 Washing off 
11.5.2.4.1 Non-washable size distemper, once widely used for ceilings, might be encountered in older 
buildings. It is essential to remove it before repainting, and this should be done by soaking the material with 
water until it has softened and can be sponged, scrubbed or scraped off.  
11.5.2.4.2 Other water-borne coatings, including some water-borne paints, while not soluble in water might 
lose adhesion when thoroughly wetted to an extent that permits their removal (see also 11.5.2.7). 
11.5.2.5 Scraping 
Coatings having poor adhesion, locally or generally, can often be removed by scraping, without recourse to 
burning off or the use of paint remover. When local areas of poorly adhering material are removed in this way, 
it should be ensured that adhesion of the remainder is satisfactory and that the defective coating is removed 
back to a firm edge. 
11.5.2.6 Abrasion 
11.5.2.6.1 Abrasion includes hand or mechanical sanding, abrasive discs and pads and wire brushing and 
should be used for removing perished, heavily chalking or poorly adhering coatings. It might be the only 
practicable method of preparing external walls having an accumulation of coatings of miscellaneous type in 
poor condition. In such circumstances, complete removal of the residues of old coatings back to a sound 
surface might be difficult and application of a primer-sealer (5/3), after thorough preparation, might be 
necessary (see 11.5.5).  
11.5.2.6.2 Precautions should be taken to prevent inhalation of dust and to protect eyes (see Annex B). 
11.5.2.7 Steam stripping 
Steam stripping equipment involves steam being generated and supplied to a perforated pad held against the 
surface from which a coating is to be removed. The equipment was designed originally for use in the removal 
of wallpaper but has been found to be of assistance in the removal of water-borne paints from interior walls 
and ceilings. Steam stripping should be used for large areas, as it can be more effective than the washing-off 
method referred to in 11.5.2.4. DRS 554: 2022 
109                ©RSB2023- All rights reserved 
 11.5.2.8 Abrasive blasting 
11.5.2.8.1 Abrasive blasting blasting (see 8.3.4.2.1) can be used for the removal of heavy accumulations of 
old coatings from external wall surfaces, and consideration should be given to its use when warranted by the 
condition of the coatings and the extent of the areas. To avoid possible damage to the substrate, care should 
be taken in the selection of abrasives and air or water pressures, and the work should be carried out only by 
experienced contractors.  
11.5.2.8.2 High-pressure water cleaning, referred to in 11.5.3, can also be an effective method of removing 
old coatings from external walls. 
11.5.3 Cleaning 
11.5.3.1 If coatings are generally in sound condition and of types not likely to be affected by wetting, 
superficial dirt should be removed by washing with a solution of sugar soap, household detergent, cleaning 
powder or mild soap. Strongly alkaline solutions, which can attack the coating or leave undesirable residues, 
should not be used. Proprietary cleaning materials should be used strictly in accordance with the 
manufacturer's instructions. With all types of cleaning solutions, final rinsing with clean water before the 
solution has dried is essential. After rinsing, surfaces should be dried off and time be allowed for absorbed or 
trapped moisture to dry out before coatings are applied.  
11.5.3.2 Washing might not be advisable for water-borne coatings, including some water-borne paints, 
whose adhesion might be impaired by excessive wetting. Most good quality water-borne paints will, however, 
withstand sponging with a mild cleaning solution and even light scrubbing of soiled areas. If there is any doubt 
about the advisability of wetting the surface, cleaning should be limited to dry abrasion and dusting off.  
11.5.3.3 Washing with cleaning solutions might not remove contaminants such as oil, grease, silicones 
and wax polish, which can impair the adhesion or prevent the drying of coatings. Contamination of this kind is 
likely to be encountered in industrial buildings, but it can also occur in other situations, especially around 
opening edges of doors or on skirtings adjacent to polished floors. Light contamination can be removed by 
wiping with a clean cloth and proprietary cleaner followed by washing with cleaning solution and rinsing with 
clean water. Proprietary emulsion cleaners or degreasing solutions should be used for the removal of silicones 
or heavy deposits of oil or grease, as necessary.  
11.5.3.4 High-pressure water cleaning equipment can be used when soiling is heavy and the area to be 
cleaned is extensive. Equipment is available which delivers hot or cold water or detergent solutions at 
pressures of 7.0 MPa (1 000 lbf/in2) or higher. 
11.5.4 Abrasion (rubbing down) 
NOTE Abrasive materials and methods are described in 9.2.3. 
11.5.4.1 Gloss coatings should be abraded to provide adhesion for the new coating, care being taken not 
to cut through to the substrate. Abrading assists cleaning and can be combined with washing by using 
waterproof abrasive paper. Lead-based paint surfaces should be wet-abraded (see B.1.2)  
11.5.4.2 Surfaces from which coatings have been removed by burning off or with paint remover, should 
then be abraded.  
©RSB 2023- All rights reserved                  110 
 11.5.5 Priming 
11.5.5.1 Surfaces from which coatings have been removed should be primed depending upon the nature 
of the substrate and the type of coating to be applied. Reference should be made to the appropriate substrate 
in Clause 8 for guidance.  
11.5.5.2 As noted in 11.5.2.6, it can be difficult to remove perished, heavily chalking or poorly adhering 
coatings completely, especially from external walls. Preparation, usually by thorough scraping and brushing, 
should be followed by application of a primer-sealer (5/3) to bind any residual material and reduce the risk of 
subsequent flaking. It is emphasized that application of a primer-sealer is supplementary to thorough 
preparation; too much reliance should not be placed on the ability of these materials to penetrate multiple 
layers of old coatings. Penetration can be assisted by thinning, but the manufacturer's recommendations 
regarding this should be followed.  
11.5.5.3 Glazing rebates, exposed by the removal of defective putties, should be primed before re-
applying putty.  
11.5.5.4 If discoloration or staining of the existing paint has occurred (see 11.5.9), a sealer should be 
applied, as necessary. 
11.5.6 Stopping and filling 
The materials and methods employed in filling should be selected in accordance with 7.4.4 and 9.2.4 
respectively. 
11.5.7 Bringing forward 
Bringing forward refers to the repair of localized areas, e.g. where defective paint has been removed and the 
substrate is exposed to provide a uniform surface before application of finishes. Treatment will depend upon 
the nature of the substrate and of the existing system but, typically, should include priming, stopping and filling 
and the application of further coats to restore the original film thickness. 
11.5.8 Treatment of biological growth 
11.5.8.1 General 
The information in this sub-clause is based upon that given in BRE Digest 370 [6] to which reference should 
be made for a more comprehensive treatment. 
11.5.8.2 External surfaces 
11.5.8.2.1 Lichens and mosses are often found on roofs and external walls especially in rural areas. Their 
appearance is often regarded as pleasing but, if the surfaces are to be painted, the growths have to be 
removed. Algae occur in most districts when water runs freely over a surface; they cause unsightly green or 
black stains and have to be removed before painting. Moulds and algal growths resembling dirt deposits can 
occur outdoors on paints and wood stains; in the early stages they can be washed off, but moulds can 
penetrate and damage the existing coatings and affect the new one.  DRS 554: 2022 
111                ©RSB2023- All rights reserved 
 11.5.8.2.2 Where growths are present on surfaces that are to be painted, preparatory treatment should 
include application of a surface biocide.  
NOTE 1 Active chemicals used in surface biocides are subject to scrutiny for safety in use under the Control of Pesticides 
Regulations 1986 (as amended) [11] and require that only products with an HSE registration number be used. This regulation is being 
absorbed into the Biocidal Products Regulations 2001 [21], however it is an offence to use any pesticidal product without approval under 
the appropriate Regulations.  
11.5.8.2.3 The efficiency of surface biocides will vary according to circumstances, for example sodium 
hypochlorite is readily available and is effective with a wide range of growths but has no residual activity.  
11.5.8.2.4 When using surface biocides, the manufacturer's instructions should be followed regarding the 
use of protective clothing (e.g. goggles, gloves, overalls).  
NOTE 2 Professional operators will need to take into account procedures required under the Control of Substances Hazardous to 
Health Regulations 2002 (COSHH) [5] and see B.2.  
11.5.8.2.5 Surface biocides take a few days to become effective and, in wet weather, can be washed out 
before they have had tune to act. They should preferably be applied during a dry spell. To hasten the biocide 
action, thick surface growths should be partly removed or torn with a stiff but not wire brush before brushing 
the wash well in. The wash, repeated if necessary, kills the growth, but the dead organism takes some time to 
disappear. The dead matter should be removed by scraping and brushing, and this is often more effective 
when the growth is dry; however, it is important that asbestos-cement be not scraped or brushed except when 
wet. All dust and debris should be carefully collected, sealed in plastic bags and disposed of in a safe manner. 
After removal of the dead growth, a further application of surface biocide (with types having a residual effect) 
can be used to delay re-establishment of the growth.  
11.5.8.2.6 Heavy growths should preferably be removed from external walls by abrasive blasting (see 
11.5.2.8) or high-pressure water cleaning (see 11.5.3) when circumstances permit or warrant their use and 
should subsequently be treated with a surface biocide. 
11.5.8.3 Internal surfaces 
11.5.8.3.1 Mould (mildew) is the form of biological growth most likely to affect internal surfaces. The 
conditions and exposure conditions favourable to its development and measures to prevent or control it are 
described in 4.6.4.4. Preparatory treatment of painted or papered surfaces will depend upon the type of 
decoration and the extent to which it is affected.  
11.5.8.3.2 Wallcoverings should always be stripped if mould is evident on or beneath them. Paint should be 
removed if it is severely affected and the growth is deep-seated. In disposing of stripped paper or paint, care 
should be taken to avoid contaminating unaffected surfaces. After removal of wallcoverings or paints, the 
surface should be treated with a surface biocide and kept under observation for a week or so, a further wash 
being applied if growth is renewed. When growth has ceased and the surface is dry, it can be redecorated.  
11.5.8.3.3 Where infection is slight and the coating is of a type which will withstand application of a surface 
biocide, it might be sufficient to clean down without removing the coating and then to apply the wash, allow to 
dry and repaint.  
©RSB 2023- All rights reserved                  112 
 11.5.9 Stains and discoloration 
11.5.9.1 General 
Staining or discoloration evident in the existing coating might be transmitted to the new one unless preventive 
measures are taken. Constituents of the existing coating or the substrate might also cause discoloration of the 
new coating although it might not have been apparent previously. Some types of mould can cause 
discoloration but the mould itself might not be visible. Diagnosis of the causes of staining or discoloration and 
recommendations for remedial treatment can require expert investigation but some typical examples are 
described in 11.5.9.2 to 11.5.9.6. Specialist stain resistant paints are available. 
11.5.9.2 Bitumen staining (bleeding) 
Where bitumen surfaces need to be overpainted, they should be treated in accordance with 8.15. 
11.5.9.3 Knot staining 
Discoloration of paint over knots and resinous areas can be indicative of incorrect or inadequate treatment 
during initial painting and might be transmitted to coatings applied during maintenance painting. If the existing 
coating is generally in good condition, i.e. does not need to be removed, further staining should be minimized 
by applying fresh knotting or specialist knot treatment. 
11.5.9.4 Tobacco tar staining 
Tobacco tar staining is caused by the deposition of the tarry matter in tobacco smoke. It often results in severe 
yellowing or browning of painted surfaces and might cause staining and retarded drying of subsequent coats. 
To remove the deposit, the coat should be scrubbed with a solution of household detergent or cleaning 
powder. However, to reduce the risk of the new coating being affected, a coat of aluminium primer (3/4), 
primer-sealer (5/3) or a proprietary stain blocker can be applied. 
11.5.9.5 Stains from wallpaper 
Treatment might be required to prevent staining of water-borne paints applied over some types of wallpaper 
although, if there is a risk of this occurring, the wallpaper should be removed (see 8.12.1.2). 
11.5.9.6 Pattern staining 
11.5.9.6.1 Pattern staining is a thermal effect, differing rates of heat flow through a composite structure 
causing variations in the amount of dust deposited upon a surface.  
NOTE A typical example is often seen in ceilings where the presence of joists or beams is indicated by lighter or darker areas. 
Mortar joints in blockwork and fixings in claddings and linings can produce a similar effect. 
11.5.9.6.2 Paint treatment cannot significantly affect the rate of heat flow and the consequent deposition of 
dust but, where pattern staining rapidly develops, paints, which resist soiling and can withstand frequent 
washing, e.g. gloss and mid-sheen types, should be used. DRS 554: 2022 
113                ©RSB2023- All rights reserved 
 11.6 Application 
The general considerations regarding application methods and techniques as described in Clause 9 should be 
followed. Spray equipment should not be used in occupied buildings in circumstances where spray mist would 
create a nuisance (see 9,3.6.1) and petrol or diesel engine compressors should not be used in situations 
where noise and exhaust fumes should be avoided. 
  
©RSB 2023- All rights reserved                  114 
 Annex A 
(informative)  
 
Types of coatings 
A.1 General 
For the purposes of this code, paints and similar coatings are grouped in three categories as follows:  
a) conventional coatings (see A.2);  
b) specialist coatings (see A. 3);  
c) factory-applied coatings (see A.4). Metallic coatings are referred to in 8.4. 
A.2 Conventional coatings 
A.2.1 Conventional coatings represent the greater proportion of the coatings in general use in the painting 
of buildings and are based mainly on drying-oil or water-borne binders. They are listed and described in 
Tables 3 to 10, generally according to their functions within the coating system.  
A.2.2 Conventional coatings based on binders of the types referred to in Tables 3 to 10 can be modified to 
impart specific properties, e.g. of mould-resistance or fire protection (see 4.6.4). 
A.3 Specialist coatings 
A.3.1 Specialist coatings have properties, e.g. of chemical resistance, hardness or other characteristics, not 
possessed by materials of conventional type (see 4.6.4). They might require special techniques or conditions 
of application or necessitate high standards of surface preparation and might not be readily available from 
normal sources of supply. Often, the complete system is of specialist type and might not be suitable for use 
over primers or existing coatings of conventional type. For these reasons specialist coatings have limited 
usage in the painting of buildings.  
A.3.2 Table 11 summarizes the characteristics of the principal types of specialist coating. Within the generic 
categories, there can be considerable variation in the formulation and, in consequence, the characteristics of 
individual materials.  
A.3.3 Reference to manufacturer's recommendations is advised when there appears to be a requirement for 
the use of specialist coatings. BS EN ISO 12944 and ISO 14713-1 give detailed recommendations regarding 
specialist coatings for the protection of iron and steel structures.  
A.3.4 Table 11 lists specialist coatings that can give extra resistance and/or durability. These coatings can 
themselves be further modified to provide specific properties such as mould resistance or fire protection. DRS 554: 2022 
115                ©RSB2023- All rights reserved 
 A.4 Factory-applied coatings 
A.4.1 These range from stoving or air-drying paints, applied to wood and metal components by spraying or 
dipping, to coil coatings mechanically applied to coiled flat sheet for subsequent forming and fabrication. 
Coatings of types unsuitable for site application might be employed; correctly chosen and applied, they can be 
tougher, harder and more durable than most site-applied coatings. These coatings can all be overpainted for 
aesthetic or maintenance purposes, by the correct choice of primer and top coat. The most common factory 
applied coating is PVC plastisol but more variation in coating types now exists (see 8.13.4).  
A.4.2 For light gauge steel, ISO 14713-1 gives guidance in choice of coatings, although there have been 
improvements in and additions to the types there described. Organic coatings for aluminium extrusions (e.g. 
windows) are defined in BS 4842, and the expected performance of a variety of coatings on metal and other 
claddings is tabulated in BS 5427-1. No such guidance is available for complete factory-applied systems on 
timber, but they can give better durability than the conventional site-applied coatings at no greater cost.  
A.4.3 Components for interior use are sometimes coated by processes suitable for the dry conditions of a 
completed building, but inadequate for exposure to weather or condensation during erection. To avoid 
premature failure, a higher grade coating might have to be specified. Likewise, the life indicated for various 
categories could be extended by additional coats or increased thickness. 
   
©RSB 2023- All rights reserved                  116 
 Annex B 
(normative)  
 
Health and safety 
NOTE The list of health and safety hazards in Annex A does not purport to be exhaustive. 
B.1 Hazards 
B.1.1 General 
The materials used for painting buildings are made from a wide range of chemical substances, some of which 
are toxic. However, if suitable precautions are taken, these materials can be used without risks to health.  
NOTE The Control of Substances Hazardous to Health Regulations 2002 (COSHH) [9] require employers to assess the risks which 
might arise from hazardous substances at work and then to determine the measures needed to prevent or adequately control exposure to 
them. For further information see HSE publication HSG 97, A step by step guide to COSHH assessment [22].  
The risk of exposure depends on the nature of the materials used, the conditions of use and the way in which 
preparation is implemented.  
It might be possible to eliminate a hazardous substance either by changing the process or substituting a safe 
or safer substance. Where this is not reasonably practicable, exposure should be controlled by, for example, 
enclosure, the use of ventilation equipment, general ventilation, safe systems of work and handling 
procedures. Personal protective equipment should only be used where other measures cannot adequately 
control exposure.  
In addition to the manufacturer's recommendations, precautions to be taken by those engaged in the painting 
of buildings should include the following.  
a) The least hazardous product and system of working should be used.  
b) Overalls should be worn while working but should be removed before eating and before leaving work. 
They should be laundered at frequent intervals. Gloves, goggles and a suitable respiratory protection 
should also be worn when a hazard exists.  
c) Reasonable measures should be taken to keep painters' materials off the skin, and hands should be 
washed before eating or drinking. Silicone-free barrier creams should also be used. Smoking while 
working should be discouraged since this can cause paint to be transferred to the mouth.  
d) It is essential that paints, solvents and other painters' materials are not placed in containers normally used 
to hold food or drink, and they should be kept out of reach of children and animals. Residues should be 
disposed of safely.  
e) If paint, solvent or other material is accidentally swallowed, medical attention should be sought 
immediately.  DRS 554: 2022 
117                ©RSB2023- All rights reserved 
 f) Adequate ventilation, either mechanical or natural, is essential. 
B.1.2 Lead paints 
B.1.2.1 The use of lead paints has declined in recent years but surfaces in older buildings might have 
been painted with lead paints. If this is the case, the dust created by dry abrasion is a hazard; and so wet 
abrasion (see 9.2.3) should be undertaken as it is safer and also more effective.  
NOTE Because of the possible toxic hazard involved, the use of lead paints and the preparation of lead-painted surfaces are 
subject to legislation Control of Lead at Work Regulations [8]. For further information on lead and its exposure levels at work see HSE 
publications LI 32, Control of lead at work [23] and EHW/2005, Workplace exposure limits [24].  
B.1.2.2 Lead paints should not be used on surfaces which might be licked or chewed by children or 
animals. 
B.1.3 Fungicidal washes and coatings 
Some coatings and preparatory washes might contain or be based on materials intended to inhibit moulds or 
other biological growths (see 11.5.8). While the use of inhibitors having atoxic effect on humans or animals is 
unlikely, the manufacturer's recommendations regarding their application and also their use on surfaces in 
contact with foodstuffs should be strictly observed. 
B.1.4 Vapours, fumes and dusts 
B.1.4.1 Inhalation of of solvent vapours in high concentrations can cause narcosis and can affect the 
respiratory or digestive systems. Irritation of the eyes, nose and throat can also occur. These effects should 
be prevented by ensuring that there is sufficient ventilation of the compartment being painted to control 
solvent vapour concentrations.  
NOTE 1 Attention is drawn to the Control of Substances Hazardous to Health Regulations 2002 [9]. Occupational exposure limits, 
which should be used for the purposes of these Regulations, are reproduced in HSE Guidance Note EHW/2005 [24].  
B.1.4.2 If solvents, notably white spirit, are used for cleaning, only the minimum amount necessary should 
be employed. Skin contact with the solvent should be avoided (by wearing suitable protective gloves) and, as 
with painting, the work area should be well ventilated to prevent the build up of solvent vapours. Sufficient time 
should be allowed for solvent to evaporate before work proceeds.  
B.1.4.3 Chlorinated solvents such as dichloromethane, that are used in some paint removers (see 
11.5.2.3), are much more volatile than ordinary paint solvents, and the vapours, if allowed to accumulate, are 
powerful anaesthetizing agents. Also, if the vapours come into contact with flames or red-hot surfaces, they 
might decompose to form toxic substances. Accordingly, when using paint removers containing chlorinated 
solvents, it is essential that adequate ventilation is provided and that sources of ignition, including lighted 
cigarettes and pipes, are excluded from the working area.  
B.1.4.4 Certain types of paint present particular toxic problems when applied by spraying. These include, 
for example, two-pack epoxy coatings, which can be potent skin and eye irritants, and two-pack polyurethane 
paints which contain isocyanates and present serious health hazards through inhalation of paint mists. 
Precautionary measures should be taken to prevent exposure to mist and vapour arising from their use, as 
both of these classes of paint can cause sensitization. When this is not reasonably practicable, a very high 
standard of control measures should be taken.   
©RSB 2023- All rights reserved                  118 
 B.1.4.5 There should be sufficient flow of air through compartments being painted in order to control 
solvent vapour concentrations adequately. Under some circumstances this may be achieved by natural 
ventilation, i.e. by means of windows or doors that open directly to outside the building. Where natural 
ventilation on its own is not always reliable and might not always provide a sufficient flow of fresh air through 
the space or where natural ventilation is not possible (e.g. in underground and windowless compartments, 
pits, tank interiors, operating theatres etc.), a mechanical means of ventilation should be provided.  
B.1.4.6 Factors such as the wind conditions outside the building, the volatility of the solvents involved, the 
rate of application of the paint and the surface area to be coated should be taken into account when deciding 
upon the method and extent of ventilation. In difficult or unusual circumstances, professional advice on 
ventilation should be sought.  
B.1.4.7 Where vapours are created, for example in the spray application of two-pack polyurethane paints 
and epoxy surface coatings, or where surface preparation work creates dust and fumes, this should be 
regarded as potentially hazardous to health. Where it is not possible to control exposure to vapours, dust and 
fumes adequately by other means, then suitable respiratory protective equipment should be worn. It is also 
recommended that accumulations of dust on floors, ledges etc. should be removed with an industrial vacuum 
cleaner rather than by sweeping.  
NOTE 2 Respiratory protective equipment can be regarded as suitable if it is a type-approved by the Health and Safety Executive 
(HSE) or conforms to a standard approved by the HSE. For further information on respiratory protective devices, see BS 4275 and HSE 
Guidance Note EH/16, Isocyanates: Health hazards and precautionary measures [25]. For further information on protection against dust, 
see HSE Guidance Note EH/44, Dust: General principles of protection [26]. 
B.1.4.8 Special precautions should be taken in work involving building materials containing asbestos.  
NOTE 3 Attention is drawn to the Control of Asbestos at Work Regulations 2002 [27], which requires that any asbestos- containing 
material is assessed for the likelihood of release of asbestos fibres if disturbed, and that a safe working environment is maintained with 
respect to all asbestos materials identified. The supply and application of paints and varnishes containing asbestos are not permitted 
under the Asbestos (Prohibitions) Regulations 1992 [28] made under the Health and Safety at Work etc. Act 1974 [29], In case of doubt or 
for detailed guidance, reference can be made to the Health and Safety Executive and to HSE Guidance Notes HSG248, Asbestos: The 
analysts' guide for sampling, analysis and clearance procedures [30] and HSE Guidance Notes EH40/2005, Workplace exposure limits 
[24] (see also K.3.2 and K.3.3). 
B.2 Injury to eyes and skin 
B.2.1 Materials such as paint removers, alkaline cleaning solutions and some of the inhibitive washes 
referred to in 11.5.8 can cause serious injury if they enter the eyes. They might also have a harmful or irritant 
effect on the skin. When these and materials of a similar type are used, measures should be taken to prevent 
them from coming into contact with the skin. Where the circumstances or conditions of working are such that 
heavy contamination of the hands cannot be avoided, impervious industrial gloves should be worn.  
B.2.2 Eye protection should be worn, especially when working overhead. Eye protection should be used 
during paint spraying and during surface preparation work such as chipping, scraping and mechanical 
sanding, as necessary.  
NOTE Attention is drawn to Personal Protective Equipment at Work Regulations 1992 [31], which cover all equipment designed to 
be worn or held to protect against a hazard where risk cannot otherwise be adequately controlled. See also the Control of Substances 
Hazardous to Health Regulations 2002 [9]. 
B.2.3 Hands and exposed areas of skin should be treated with silicone-free barrier cream before work 
starts, and should afterwards be cleaned with an approved hand cleaner. Hands should not be cleaned with 
paint solvents or thinners as this might result in skin complaints or the absorption of materials through the DRS 554: 2022 
119                ©RSB2023- All rights reserved 
 skin. Over-vigorous scrubbing or the use of harsh cleaning powders or soaps should be avoided as it might 
also cause skin complaints.  
B.2.4 Impervious industrial gloves should be used if heavy hand contamination is likely. 
B.3 Fire an explosion 
B.3.1 Many of the materials used by painters are flammable or will support combustion, so that suitable 
precautions should be taken in their storage, handling and use.  
NOTE 1 Highly flammable liquids (paint solvents such as toluene or xylene) are the subject of legislation and there are statutory 
requirements with regard to their labelling, storage and use. Attention is drawn to the Highly Flammable Liquids and Liquefied Petroleum 
Gases Regulations 1972 [32] apply to the storage and use of certain flammable liquids.  
B.3.2 Precautions should be taken to ensure that vapours of highly flammable solvents do not accumulate 
in a space or part of a space, which is being painted, as a potentially explosive mixture with air could 
eventually be reached. The vapour concentrations required to produce such a mixture (i.e. the lower explosive 
limit or LEL) are about 1% (v/v) in air and ventilation should be provided to ensure that 0.1% solvent vapour in 
air is not exceeded which gives a ten-fold safety margin.  
NOTE 2 Attention is drawn to HSE Guidance Notes L101, Safe work in confined spaces [33] and HSG178, The spraying of 
flammable liquids [34].  
B.3.3 It should be remembered, however, that there can be circumstances where breathing zone 
concentrations might be low but where pockets of high vapour concentrations nevertheless build up quickly 
due to poor art distribution, for example in pits and similar confined spaces. It is thus important to ensure that 
there is good air distribution throughout the whole space and to recognize that this might require the provision 
of additional means of mechanical ventilation or dispersion to deal with such areas in which there would 
otherwise be httle or no air movement. 
B.3.4 Sources of ignition such as lighted cigarettes, matches, blow lamps, elements of electric fires, 
unprotected light bulbs, electric motors which are not flameproof, etc. should be eliminated from any area 
where a flammable concentration of vapour might be present or arise.  
B.3.5 Rags soaked with paint can ignite spontaneously if they are tightly compressed in, for example, bins 
or in the pockets of overalls. They should be spread out in the open air outside the building to dry off, or 
placed in a metal bin with a close-fitting lid.  
NOTE 3 For further information, reference can be made to the advice given in the HSE publication HSG168, Fire safety in 
construction work [13]. 
B.4 Noise 
Precautions should be taken against exposure to noise levels, as prolonged exposure to a high noise level, 
e.g. from compressors and mechanical tools, can damage the hearing of operatives and others nearby.  
NOTE Information on noise levels and the corresponding maximum exposure times is given in the Noise at Work Regulations 1989 
[35]. Further information can be found in the HSE publication L108, Reducing noise at work [36] (see also BS 5228).  
©RSB 2023- All rights reserved                  120 
 B.5 Spillages 
Spillages of paint should be cleaned up as soon as they occur, with an inert absorbent material. The use of 
rags and sawdust should be discouraged. If used, they should be disposed of safely. The area should be well 
ventilated to remove solvent fumes, and sources of ignition should be eliminated. 
B.6 Waste disposal 
Care should be exercised when disposing of waste, in particular if there could be heavy metal, e.g. lead, 
contamination of the waste.  
NOTE Attention is drawn to Hazardous Waste (England and Wales} Regulations 2005 [37] which set out the regime for the control 
and tracking of the movement of hazardous waste for the purpose of implementing the Hazardous Waste Directive (91/689/EC) [38]. DRS 554: 2022 
121                ©RSB2023- All rights reserved 
 Annex C 
(informative)  
 
Wood 
C.1 Design considerations 
Timbers can be broadly divided into softwoods and hardwoods, and a range of species from both classes is 
employed in construction. Softwood timbers, derived from coniferous trees and which include species such as 
pine, spruce and fir, account for the greater volume of timber used. They are relatively soft, easy to work and 
finish, though some species can present specific coating problems. Hardwood timbers derived from broad-
leaved, deciduous trees are used in the UK selectively in smaller volume. They are in general heavy, hard and 
close grained, and include many of the highly figured and highly coloured timbers valued for internal work. 
Many tropical hardwoods and some temperate species such as oak and chestnut also possess advantages in 
terms of dimensional stability, moisture impermeability and decay resistance. The structure and properties of 
wood can have an important influence on the specification of the coating system, and on its subsequent 
performance in service.  
Coating of wood might be required for purposes of decoration and protection. The decorative effect often 
derives from the colour and sheen of a paint coating, but wood is also one of the few substrates for which 
there is a demand for transparent coatings that present and enhance the visual appeal of the substrate. 
Protective purposes include the following.  
a) Sealing. Untreated wood surfaces absorb liquids, are subject to soiling and chemical staining, and are 
unhygienic and difficult to clean.  
b) Mechanical damage. Resistance to scratching and abrasion is an important requirement for flooring and 
some other internal applications.  
c) Stabilization. Surface coatings have a major effect on the rate of exchange of water vapour between wood 
and the surrounding atmosphere, and hence can be an effective means of controlling the swelling and 
shrinking of the wood.  
d) Weather protection. Wood surfaces exposed to the weather without surface protection are subject to 
discoloration,  
e) defibration  
f) and greying.  
g) Preservation and protection. Surface coatings cannot generally be classed as wood preservatives as they 
are not toxic to wood destroying organisms and do not penetrate sufficiently deeply. Moreover in some 
circumstances paint can trap water in the wood and increase any risk of decay. Nevertheless an intact 
paint film on all surfaces will prevent the wood becoming wet enough to support fungal growth, and will 
prevent the surface being colonized by moulds and other fungal spores. In this restricted sense paint 
contributes to the preservation of the wood surface.   
©RSB 2023- All rights reserved                  122 
 h) Flame retardance. Coatings can be applied to wood and wood-based panel products to raise the 
resistance to spread of flame. 
C.2 Characteristics 
C.2.1 Structure 
C.2.1.1 The properties encountered with wood are directly related to the origins of the raw material, 
namely the structure and functions of a tree. Wood is a cellular material in which most of the cells are aligned 
vertically in the tree, giving wood its characteristic grain. Other cells lie in horizontal bands (rays) running 
outwards in the tree. 
C.2.1.2 Moisture uptake in wood arises from the natural liquid pathways found in the growing tree and will 
occur in softwoods and hardwoods. 
C.2.2 Heartwood and sapwood 
The trunk of a young tree consists entirely of sapwood, which not only provides mechanical support but also 
sap conduction processes essential to the life of the tree. As the tree ages, a core of heartwood develops 
which plays no part in fluid conduction and which gradually becomes impregnated with a wide range of resins, 
gums, tannins and other chemicals. Heartwood is often distinguished from sapwood by its deeper reddish-
brown colour, and in most wood species possesses greater resistance to water uptake and a degree of 
natural decay resistance. In general, the sapwood of timber is moisture permeable and susceptible to fungal 
decay, and its effective protection poses a greater challenge when used in applications where it is at risk of 
wetting. 
C.2.3 Moisture content 
Green timber contains both free water in the cell cavities and water absorbed by the cell walls. Reducing the 
moisture content to a mass fraction of about 25% to 30% of the oven-dry mass removes free water from the 
cell cavities, but the fibres remain saturated and the wood is fully swollen; it shrinks progressively as more 
moisture is removed. Shrinkage is greatest across the grain and is reversible; changes in moisture content 
through exposure to ram or fluctuations in relative humidity cause alternate swelling and shrinkage. 
C.2.4 Permeability and penetration of liquids 
C.2.4.1 The permeable nature of wood affects not only moisture movement but also the ease of 
impregnation by preservatives and the behaviour of paint.  
C.2.4.2 In general, penetration is deeper and more rapid through end grain than through lateral surfaces, 
and is also deeper and more rapid through sapwood than through heartwood. There are also differences in 
permeability between early and late growth areas causing differential swelling which imposes stresses on 
surface coatings. 
C.2.5 Extractives 
C.2.5.1 Extractives are present as minor non-structural constituents of the cell-cavities and cell walls, and 
differ greatly in quantity and type in different wood species. In most species, the extractive content averages 
less than a mass fraction of 5%, but in some tropical hardwoods, and in the knots of many softwoods, it can DRS 554: 2022 
123                ©RSB2023- All rights reserved 
 amount to a mass fraction of 30% or more. The chemical nature of the extractives in both hardwoods and 
softwoods is very variable.  
C.2.5.2 One of the most commonly encountered extractive problems is associated with knots in resin-rich 
softwoods such as Scots pine (European redwood) and British Columbian pine (Douglas fir). These resins 
basically consist of a blend of resin acids or rosin in turpentine, together with small amounts of tannins, which 
are water-soluble and possess the property of darkening on exposure to light. The resin blend gives rise to 
two kinds of problems. In hot summer weather they are mobilized and exude to the wood-paint interface 
where they cause blistering of the paint. This problem is most severe when dark coloured paint has been 
used, and can also be aggravated by retained solvent from preservative treatment. The tannin extractives can 
additionally migrate into the paint to produce a brown discoloration in the area of paint over the knot, which is 
particularly noticeable on white and pastel shades, and especially on water-borne coatings. For such timbers 
coated with wood stains, the resin can penetrate through the film without disrupting it or causing blisters. 
C.2.6 External influences – Moisture 
C.2.6.1 As a result of increased attention to heat conservation, internal condensation has assumed 
considerable importance as a source of moisture. The absence of flues, blocking of unused flues and 
airbricks, draught-proofing and similar measures have greatly reduced internal ventilation rates, especially in 
domestic buildings. In consequence, the water vapour produced by normal domestic activities is unable to 
escape readily and can migrate to colder rooms and condense on single-glazed windows, eventually 
penetrating open joints, defective putties and other discontinuities in the paint film. This is a frequent cause of 
timber decay and paint failure on wooden window frames and sills. Wet rot in timber cladding or failure of the 
external paint can also be caused by condensation within the wall cavity.  
C.2.6.2 Coating permeability has important implications on timber windows. These are usually subject to 
a higher temperature and relative humidity on the inside compared with the outside, and a consequent vapour 
pressure differential favouring the transport of warm moist air outwards through the timber frame sections. 
One of the functions of the interior paint is to provide a vapour barrier, and it is essential therefore that it 
possesses a relatively low permeability. Circumstances in which the inside coating is more moisture 
permeable than that outside, as for example through the use of a permeable water-borne paint inside and a 
solvent-borne alkyd outside, need to be avoided. This arrangement can result in interstitial condensation 
within the frame section and severe blistering of the exterior coating during cold weather. 
C.2.7 Preservative treatments 
Preservative of wood components such as exterior softwood joinery and cladding is desirable and is normally 
carried out in the factory. The main types of preservative used are organic solvent solutions of fungicides or 
water-borne micro emulsions applied by double-vacuum treatment or immersion. For cladding and outdoor 
applications, vacuum-pressure treatment with water-borne salts or fungicides are also employed. 
C.2.8 Knot treatment 
C.2.8.1 Knotting is rarely effective in preventing physical disruption of paint films by heavy exudation of 
resin. This is more likely to occur externally over knots in surfaces exposed to strong sunlight, which liquefies 
the resin and makes it more active. The use of light-coloured paints reduces solar heat gain and can therefore 
reduce resin exudation although it is unlikely to prevent it completely; also, the resin will be more obvious on a 
light-coloured surface. An alternative is the use of an exterior wood stain (see 8.1.8.3).  
C.2.8.2 The widespread adoption of water-borne paints has given rise to significant problems of staining 
over knots due to extraction of light-sensitive tannins contained in the knots into the coating (see C.2.5).  
©RSB 2023- All rights reserved                  124 
 Conventional knotting is relatively ineffective in preventing tannin staining; more successful results have been 
achieved through the use of stain-blocking primers containing reactive pigments. 
C.2.9 Coating systems for interior use 
C.2.9.1 Paint systems 
C.2.9.1.1 Water-borne paints 
Water-borne latex paints have long been accepted in wall painting but their adoption for internal woodwork 
has been hindered by their inferior flow and initial gloss properties compared with the traditional solvent-borne 
alkyd. They have significant application advantages however, in particular low odour and rapid rate of drying 
which can permit the complete system to be applied in the working day. 
C.2.9.1.2 Transparent and semi-transparent finishes 
The provision of a clear seal or varnish finish to interior wood is a relatively straightforward operation and a 
wide variety of coating systems is available for this purpose. The traditional solvent-borne oil and alkyd resin 
still find application, though there are moves to reduce solvent-content and for example to use de-aromatized 
white spirit. The wood colour can be equalized or altered by the application of a dye or stain before sealing, or 
this might be achieved by the use of an interior wood stain. A full range of gloss levels is achievable, and 
where necessary coatings with good resistance to mechanical damage or staining can be obtained. Water-
borne varnishes have advanced considerably during recent years and in appearance and wear resistance 
properties are now almost equivalent to the established solvent-borne types. 
C.2.10 Coating systems for exterior use 
C.2.10.1 General 
C.2.10.1.1 Although decorative effect is important for exterior wood coatings, the function that is of vital 
importance is the protection of the wood substrate against deterioration by weathering agencies, principally 
sunlight and water, and biological attack. Exterior wood is moreover a very challenging substrate, in that any 
adventitious entry of water can lead to dimensional movement in the substrate, biological deterioration, and 
adverse effects on coating adhesion.  
C.2.10.1.2 Much dissatisfaction with the performance of exterior wood coatings over the years has been 
caused by the use of unsuitable general-purpose alkyd-based paints that lacked sufficient flexibility to cope 
with the demands of an unstable wood substrate. In order to aid the selection of suitable coatings, 
considerable effort has been devoted to the development of performance standards. ISO 16053 specifies a 
system for the classification of coating materials and coating systems for exterior wood surfaces by categories 
of end use, appearance and exposure conditions. The natural exposure test has also been incorporated in a 
East African Standard for undercoat and gloss paints, RS EAS 1055. BS 7956 is a performance standard 
covering the performance evaluation of all classes of wood primers, namely solvent-borne, water-borne, 
aluminium and stain basecoats. It is advised that the standards of performance set in these standards are 
regarded as a minimum requirement for wood coatings. DRS 554: 2022 
125                ©RSB2023- All rights reserved 
 C.2.10.2 Exterior wood stains 
C.2.10.2.1 General 
Whereas the task of protecting and enhancing natural wood indoors is a relatively straightforward matter, the 
task of preserving the natural appearance of the wood outdoors is beset with difficulties. Clear and semi-
transparent coatings lack the opaque protective pigments that are present in paints, and are in consequence 
less durable than opaque coatings so that maintenance intervals are shorter and overall costs higher. 
Crucially any breakdown of the coating exposes wood to weathering and biological attack, and often 
consequent discoloration cannot be masked by fresh application of the natural finish. 
C.2.10.2.2 Solvent-borne exterior wood stains 
C.2.10.2.2.1 Solvent-borne exterior wood stains are generally based on alkyd resins dissolved in white 
spirit. They can be grouped into two broad classes, low-build and medium-build. The low-build products are 
typically of low viscosity and the most penetrative type of wood stain. They deposit relatively thin films on the 
surface, possibly only 10 um to 15 urn for a three-coat application, so the natural features of the wood are 
least obscured. Low-build stains weather by erosion rather than by flaking, and require a minimum of 
preparation prior to recoatmg. On the other hand in exposed situations, erosion is relatively rapid and 
maintenance intervals of about three years might be appropriate. Low-build stains have high moisture 
permeabilities, and exert relatively poor control on wood moisture content. There is a risk of significant 
dimensional movement and possibly surface splitting, especially as erosion of the stain occurs during 
weathering.  
C.2.10.2.2.2 Low-build stains possess additional technical advantages. They are very tolerant of 
imperfections such as splits, knots and nail holes, and their good penetrative properties enables them to cope 
well with weather-degraded surfaces. Resin in knots can exude through the very thin surface film without 
causing disruption; when the resin acids have hardened the residue can be removed from the surface by light 
scraping.  
C.2.10.2.2.3 Medium-build stains contain a higher proportion of resin and apply a higher film thickness of 
the order of 30 (am to 40 urn for the complete system. They are less permeable than low-build types and exert 
better moisture control on the timber, thus reducing the degree of dimensional movement and risk of surface 
splitting. They are more resistant to erosion, and require less frequent maintenance than the low-build types. 
C.2.10.2.3 Water-borne wood stains 
Water-borne acrylic and alkyd resins or alkyd-acrylic blends are increasingly being used in the formulation of 
medium-build wood stains and can give good durability. However, they penetrate less deeply into wood and 
may therefore be used over a solvent-borne priming stain. 
C.3 Wood-based panels products 
C.3.1 Characteristics 
C.3.1.1 Plywood  
C.3.1.1.1 Plywood has many of the general characteristics of solid timber, including susceptibility to the 
effects of moisture although the method of construction gives it greater dimensional stability with changes in 
moisture content.   
©RSB 2023- All rights reserved                  126 
 C.3.1.1.2 Checking varies in severity according to the species of timber used for the outer veneer. It is less 
severe, for example, with African mahogany and gaboon, while Douglas fir (British Columbian pine) and 
Finnish birch are prone to severe checking. It can be assumed, however, that the species in general use are 
all liable to check when used outside. Checking affects only the surface layer of the outer veneer but, if the 
surface is painted, the cracks are communicated to the coating, allowing entry of moisture and failure of the 
paint film. 
C.3.1.2 Fibre building board, wood chipboard and plasterboard 
Painting of fibre building board, wood chipboard and plasterboard usually has a mainly decorative function, 
but it might be necessary for protection in some circumstances, e.g. with boards used externally or in 
conditions of prolonged high humidity.  
There are four main types of fibre building board as follows.  
a) Hardboard. This is of a high density and presents a smooth, slightly absorbent surface upon which a 
satisfactory standard of finish can be obtained with most types of paint including gloss finishes. Hardboard 
is available in standard and tempered grades. Tempered hardboard is impregnated with oils or resins and 
heat-treated during manufacture to improve its water resistance. Some impregnation treatments can 
slightly retard the drying of solvent-borne paints, but this is rarely serious.  
b) Mediumboard. This is less dense and usually slightly more absorbent than hardboard but has a similarly 
smooth surface upon which a satisfactory finish can be obtained with most paints including gloss finishes.  
c) Medium density fibreboard (MDF). This is manufactured by a dry process in which the primary bond is 
derived from a bonding agent. A smooth, slightly absorbent surface is presented upon which a satisfactory 
finish can be obtained with most types of paint, including gloss finishes. Edges tend to be more absorbent 
and where exposed (e.g. by machining) and requiring a decorative finish, an additional coat of primer or 
sealer might be required (see Table 18).  
d) Softboard. This is of low density and unless specially treated, e.g. surfaced or laminated, has a rough, 
highly absorptive surface upon which it is difficult to achieve a high standard of finish, especially with gloss 
finishes.  
In addition to factory-applied decorative treatments, including coatings and laminates, there are other 
treatments for fibre building boards which might affect painting. Typical treatments, and the types of boards to 
which they apply, are described as follows:  
a) Pulp or ivory surface. A surface layer of finely-ground wood fibre is incorporated during manufacture and 
gives a uniform, light-coloured surface of low porosity. This facilitates direct application, without priming or 
sealing, of water-borne paints. The treatment is available on mediumboard and softboard.  
b) Sealed. A treatment which reduces absorption and might obviate the need to apply a primer or sealer on 
site. The treatment is available with standard hardboard.  
c) Primed. The board is supplied primed with a pigmented primer ready for site coating. The treatment is 
available with standard hardboard and soft-board.  
d) Flame-retardant treatment. Chemical impregnation can render most boards flame retardant according to 
class 1 of BS 476-7:1997, but see D.3. Boards are also available with a flame retardant coating on one or DRS 554: 2022 
127                ©RSB2023- All rights reserved 
 both sides. Some impregnation treatments can affect the appearance or behaviour of paint systems (see 
8.2.2.3). The treatment is available with hardboard, medium-board and soft-board.  
e) Perforated. Boards might be perforated during manufacture to increase sound absorption as in acoustic 
tiles, or for other reasons, e.g. for decorative effect or to provide ventilation. When perforated boards or 
tiles are used for their acoustic properties, it is important that the holes do not become blocked with paint; 
to prevent this, spray or roller application of thin coats is recommended. Perforated hardboard, medium-
board and soft-board are available. 
C.3.1.3 Wood chipboard 
Wood chipboard is composed of chips or particles of wood, mainly softwood, in a synthetic resin binder. It is 
sometimes described as particle board. Fungicidal, insecticidal and fire-retardant chemicals can be 
incorporated. Small amounts of paraffin wax can be added to give limited protection against moisture 
absorption and consequent swelling of the wood chips.  
Other factory-applied treatments, in addition to decorative finishes such as surface coatings, laminates and 
veneers, include the following.  
a) Primed/filled. A paste filler/primer, off-white or grey in colour, is applied to one or both sides of the board. 
It provides a smooth, hard surface, receptive to most types of paint. Boards treated in this way and flame 
retardant according to class 1 of BS 476-7:1997 are available.  
b) Primed. A semi-transparent or opaque primer is applied to one or both sides of the board and obviates the 
need for site priming.  
c) Sealed. A clear sealer, usually polyurethane-based, is applied to one or both sides of the board. This 
gives protection against moisture penetration and also serves as a base for site-applied clear and 
pigmented coating systems.  
d) Paper-faced. Special resin-impregnated papers are applied to one or both sides of the board and provide 
a satisfactory base for painting.  
©RSB 2023- All rights reserved                  128 
 Annex D 
(informative)  
 
Fire 
D.1 General 
D.1.1 Three requirements for any fire to occur are:  
a) a fuel;  
b) an oxidizer (normally oxygen in the air);  
c) an ignition source.  
D.1.2 A complex interaction of many factors affects whether a fire occurs and what its characteristics are. 
Typically, for a solid fuel, an ignition source provides sufficient thermal energy to break chemical bonds in the 
fuel, resulting in the production of a range of volatile chemical species that forms a gas or vapour around the 
solid. A proportion of these gases or vapours are flammable, i.e. when combined with an oxidizer in the right 
ratio, can burn.  
D.1.3 Fire types have been broadly classified as smouldering or flaming but although smouldering fires 
clearly occur at a much slower rate than flaming, the general principles still apply. 
D.2 Fire behaviour of coating and substrate 
D.2.1 The interaction of a coating film and substrate in determining fire behaviour is a function of both the 
flammability properties of the paint and the flammability properties and thermal conductivity of the substrate. 
For a given flammable paint system, substrates with a relatively high thermal conductivity (e.g. metals) tend to 
conduct heat away from the paint film and can result in more difficult ignition and slower fire development. 
Substrates with a relatively low thermal conductivity (e.g. timber) might allow easier ignition and faster fire 
development.  
D.2.2 A further distinction between fires involving paint films and fires involving bulk fuels, is the relative 
importance of heat release and surface spread of flame. Both these parameters are important measurements 
in tests for fire safety. Generally, surface spread of flame is more important for paint films as the mass of paint 
film present is relatively small, and would produce a relatively low heat release. 
D.3 Fire testing and classification of construction products with coating films 
D.3.1 Attention is drawn to Building Regulations 2000: Approved Document B - Fire safety [39] which 
specifies the fire safety requirements for wall and ceiling surfaces in terms of class ratings. To conform to 
these requirements, products or systems have to be tested against either British Standard (BS) or European 
(EN) fire test procedures. For both types of procedure, fire tests are carried out on the substrate and paint film 
as a composite system.  DRS 554: 2022 
129                ©RSB2023- All rights reserved 
 D.3.2 Historically, for painted surfaces, the main testing requirements for regulatory control have been 
centred on the BS 476-7 (surface spread of flame) and BS 476-6 (fire propagation). With the advent of the 
European Construction Products Directive, a new range of European harmonized tests has been developed, 
together with a classification system. These European tests, which include BS EN13823, the single burning 
item test for measurement of heat release rate and surface spread of flame, can now be used as an 
alternative to the existing National Standard tests (e.g. BS 8202), and it is likely in the near future for Product 
Standards to be in place, allowing CE marking of construction products. The main distinction between the two 
testing regimes is that unlike the UK BS 476 tests, the European tests require products to be tested in their 
end use configuration. For example, for internal lining materials such parameters as substrate type, air gaps 
between substrate and backing, joint details, horizontal or vertical orientation have to be considered alongside 
the testing and classification result. Further, the production of burning droplets and smoke can form part of the 
final classification for a product.  
D.3.3 With paint films there is an added complication in that decoration of surfaces with paint is likely to be a 
fairly frequent occurrence in buildings, whereas the testing and classification of the product might have only 
been performed on a single layer or limited layers of paint. This is being addressed by the use of the so-called 
"blue board" substrate, which has been developed to replicate the "worst-case scenario" in terms of a 
flammable multi-layer painted surface. This proprietary flammable "blue board" comprises 10 different coats of 
paint, applied to a plasterboard substrate.  
©RSB 2023- All rights reserved                  130 
 Annex E 
(informative)  
 
Anti-graffiti treatments 
E.1 General 
All substrates are vulnerable to disfigurement by graffiti and present different types of problem for protection or 
removal. Masonry and concrete have characteristics that include porosity, which render removal particularly 
difficult, thus protective measures are important. New products are constantly emerging to protect surfaces 
but specialist advice is also needed.  
The main technical options for graffiti control on masonry and concrete can be classified under:  
a) removal:  
1) physical means;  
2) chemical means;  
b) prevention:  
1) new surfaces;  
2) established surfaces;  
3) cleaned surfaces;  
c) obliteration:  
1) by "normal" coatings;  
2) by selected graffiti resistant coatings. 
E.2 Removal 
E.2.1 The choice of materials and methods to remove graffiti will depend on many factors including the 
nature of the marker and the substrate.  
E.2.2 The range of markers used by "graffitists" is potentially very wide and could in principle include the 
most durable coating types. Although some graffitists do go to some lengths to use markers that resist 
removal (e.g. leather dyes), the majority appear to use commercially available aerosol spray paints and felt 
permanent marker pens. The latter however are used more on smooth and already coated surfaces. In the 
case of paints, the ease of removal will depend on whether they are thermoplastic or cross-linked. The cross-
linking element is typically alkyd based. A range of commercial cleaners is available which includes such DRS 554: 2022 
131                ©RSB2023- All rights reserved 
 solvents as methylene chloride, methyl pyrrolidone, acetone, trichlorethene as well as acidic and alkaline 
solutions. They may be available in solution, paste, or bandage form. Within this range there is usually at least 
one that will be effective against commercial spray paints on smooth surfaces. However, it is clear that this list 
includes many solvents that are under severe and increasing environmental constraints for VOC and other 
reasons. Their continued availability cannot be assumed.  
E.2.3 The effectiveness of removal will depend on the contact time of the solvent and is aided by 
mechanical methods including scrapers and abraders. The use of water jet sprays can be effective, especially 
when hot (including steam), and can be further enhanced with various abrasives. Unfortunately, with friable 
substrates such as concrete, this will also remove the surface leaving a clean patch, which would contrast 
strongly with adjacent un-cleaned areas. High-pressure spraying brings in additional health and safety, as well 
as operational factors. The use of abrasive methods may only achieve the desired restoration effect if the 
whole area is cleaned. Clearly economics and practicality will limit this.  
In summary it may be observed that while there are physical/chemical means for removing most common 
graffiti markers, the porosity of untreated masonry and concrete surfaces allow penetration which renders total 
removal impossible. The adage "prevention is better than cure" applies and in vulnerable areas, surfaces 
need to be treated to resist application and aid removal. 
E.3 Prevention and damage limitation – anti-graffiti coatings 
E.3.1 General 
The objective of an anti-graffiti coating is to discourage disfigurement by markers in the first place and also to 
aid removal. If the coating is effective, then discouragement arises from the experience of the graffitist when 
their efforts are easily removed. Discrete signs that such treatment has been carried out may aid this. A more 
obvious lack of surface wetting would also be a discouragement, and this may become more common as 
spray paints become water-borne. In principle, inhibitors could retard drying of alkyd paints, and extend the 
period of relatively easy removal. However, the main present purpose of anti-graffiti coatings is to aid removal. 
E.3.2 Sacrificial coatings 
E.3.2.1 Typically, these are based on wax emulsions which are blended with siloxane acrylate, or fluoro 
compounds such as polyvinylidine chloride. Surfactants aid removal of the wax carrier, which may be removed 
by hot water jet. Some commercial systems have a special removal solvent. Systems bases on solubilized 
resins may be removed with mild alkali. Although these coatings are nominally colourless, they will darken the 
substrate to a degree, since surface penetration reduces light scattering. 
E.3.2.2 Sacrificial coatings require re-coating after cleaning. 
E.3.3 Semi-permanent coatings 
These have a greater integrity than the sacrificial group and will contain typical acrylic resins as well as wax. 
The greater film integrity allows removal of the sacrificial coating with various removers, along with offending 
graffiti. The slightly higher build helps to physically block pores and prevent penetration by the graffiti marker.  
©RSB 2023- All rights reserved                  132 
 E.3.4 Permanent coatings 
E.3.4.1 Permanent coatings overlap with conventional masonry paints but are chosen to have greater 
resistance to abrasion and chemical cleaning methods. They will therefore include high performance fluoro-
acrylics and two component polyurethanes and epoxies. Such coatings needs to meet the various criteria for 
masonry coatings in terms of permeability and durability. An obvious disadvantage is that if they do become 
marked, by persistent graffiti or constant cleaning, then they will be difficult to remove, and continual 
overcoating would be impractical. On the other hand opaque permanent coatings (anti-graffiti paint), may be a 
viable option for obliterating graffiti without the need for removal. Conventional masonry paints can also be 
used for obliteration but will not be so readily cleaned if subject to further attack.  
E.3.4.2 The use of multi-colour finishes (7/14) may help to disguise residual graffiti marking.  
E.3.4.3 As an alternative to the high-build opaque treatment, some permanent low-build transparent 
systems are emerging which give long-term protection by lowering the surface energy. 
E.3.5 Application of anti-graffiti coatings 
Some anti-graffiti treatments need specialist application. Reference needs to be made to suppliers or 
independent sources that provide expertise on substrate suitability, selection of appropriate products, 
application and maintenance. DRS 554: 2022 
133                ©RSB2023- All rights reserved 
 Annex F 
(informative)  
 
Constituents of coatings 
F.1 General 
F.1.1 Most coatings consist of binder, solvent or thinner and, in paints and stains, pigment. The binder is the 
non-volatile film-forming constituent of the coating. The solvent or thinner imparts the required degree of flow 
to the binder during application; the combination of binder and solvent forms the vehicle or medium of the 
coating.  
F.1.2 Pigment provides colour and opacity and might have other functions in some types of coatings. Other 
constituents might be present to ensure the stability of the coating or to prevent deterioration in storage or to 
confer specific characteristic performance attributes, e.g. UV resistance. 
F.2 Binders 
F.2.1 General 
The nature and proportion of binder present in a coating largely determines its characteristics, e.g. method of 
drying, compatibility with other coatings, application properties, degree of gloss, durability and resistance to 
attack. A characteristic of many binders is that they are dispersions or solutions of synthetic or natural resins 
or polymers. Individual resins and other film-forming materials differ widely in properties and provide the basis 
for a great variety of coatings. The types of binder in general use are described in F.2.2 to F.2.7. 
F.2.2 Solvent-borne binders 
F.2.2.1 Many vegetable oils, notably linseed, soya and tung oils, dry slowly to form tough, elastic films 
when exposed to air. A few primers and finishes employ binders of this type but more commonly drying oils 
are chemically combined with resins to produce an oil-modified polyester, usually referred to simply as alkyds. 
These alkyds can be further modified by the inclusion of other resins, e.g. polyurethane, polyamide or silicone, 
to impart specific properties such as hardness, gloss retention, thixotropy or flexibility. Alkyds are used to 
produce clear coatings (varnishes) or, when pigmented, paints.  
F.2.2.2 Coatings based on drying-oil type binders harden by reacting with oxygen in the air and are 
characterized by being relatively slow in drying and hardening compared with water-borne dispersions. The 
actual rate depends upon then* composition and the conditions of application, but typically they are dry to 
touch in 4 h to 8 h and re-coatable overnight. Initial drying and hardening is slower or can cease altogether in 
cold or damp conditions or in atmospheres where the movement of air is restricted. Drying and hardening can 
also be retarded by the presence of grease or dirt on the surface to which the coating is applied, and by some 
extractives in wood.  
F.2.2.3 Drying-oil and alkyd type coatings are traditionally organic solvent-thinned, usually with white 
spirit, although the manufacturer's recommendations in this respect needs to be observed (see F.3). However, 
it is also possible to solubilize or emulsify alkyds in water, thus moving them into the category of water-borne. 
Conversely, acrylic resins may be polymerized into aliphatic hydrocarbons by a process analogous to the  
©RSB 2023- All rights reserved                  134 
 "emulsion polymerization" referred to in F.2.3. These are described as "non-aqueous dispersions" or NADs, 
and may be blended with solvent-borne alkyds. 
F.2.3 Water-borne binders 
F.2.3.1 The term "water-borne binders" covers a variety of polymer types carried in water as solutions, 
emulsions or dispersions. By far the most common are polymeric dispersions (e.g. vinyl, acrylic, styrene-
acrylic) made by a process called "emulsion polymerization". This type of binder, and the paints derived from 
them, are often described as emulsion-binders, and emulsion paints. Strictly speaking this term is incorrect, as 
the term emulsion is technically used to describe one liquid dispersed in another, such as the alkyd emulsions 
described above. Water-borne dispersions are also sometimes described as "latexes" by analogy with natural 
rubber latex.  
F.2.3.2 Drying and hardening of water-borne dispersions proceed by evaporation of the water followed by 
coalescence of the particles. To aid the latter stage, many dispersions contain additional water- miscible 
solvents known as coalescing agents. In favourable circumstances, they are dry to touch or even re-coatable 
in 1 h to 2 h, and full washability is attained within a day or so of application. Damp atmospheres retard 
evaporation and cause delay in drying while very low temperatures can prevent coalescence and produce an 
unsatisfactory film.  
F.2.3.3 Water-borne acrylic and vinyl dispersions were originally used mainly as coatings for walls and 
ceilings, but as a result of substantial technical development, they can compete with solvent-borne alkyds in 
most sectors with the added advantage of low odour and VOC. Also, water, rather than expensive thinners, 
can be used for thinning and for cleaning tools and equipment after use. However, there are numerous 
detailed differences in areas, such as flow, grain-raising and poor penetration of wood, and initial gloss. 
Water-borne glosses have a lower gloss than alkyd paints, though their gloss retention is usually better.  
F.2.3.4 It is partly for this reason that there has been a growth in the use of water-borne alkyd emulsions, 
which combine some alkyd properties with the advantages of water. They still dry by auto-oxidation and will 
yellow and embrittle more on ageing than do acrylics. As a consequence of this, alkyd emulsions are 
sometimes blended with water-borne acrylic dispersions to produce hybrid binders of intermediate properties. 
Such hybrids are used in some wood-coatings. 
F.2.4 Chemically-curing binders 
F.2.4.1 Coatings employing chemically-curing binders are supplied as two-pack materials, one container 
holding the base and the other the appropriate quantity of curing agent, hardener or activator. The two 
components are combined shortly before use to induce a chemical reaction, which converts the applied film 
from a liquid to a solid state.  
F.2.4.2 Typical examples utilize epoxy or polyurethane resins and are available as clear or pigmented 
coatings. These are resistant to chemical attack and abrasion but require high standards of surface 
preparation. Curing of the film is temperature-dependent and is slowed or can be inhibited completely at low 
temperatures. These factors tend to limit the use of coatings of this type on building surfaces.  
F.2.4.3 Epoxy and polyurethane resins can be combined with other resins, notably alkyds, to produce 
one- pack materials, but these are not chemically-curing and do not have the degree of chemical and abrasion 
resistance characteristic of the two-pack types.  
F.2.4.4 Two-pack chemically-curing binders are usually carried in solvent but some water-borne types are 
available. DRS 554: 2022 
135                ©RSB2023- All rights reserved 
 F.2.5 Lacquers 
F.2.5.1 In lacquers, film-forming material is in solution (solution-binder), and conversion to the dry film is 
accomplished by evaporation of the solvent alone. Examples include solutions of shellac (knotting), vinyl-type 
resins and nitrocellulose.  
F.2.5.2 The properties of lacquers vary considerably, however, a general characteristic is that they tend 
to remain more or less soluble in the original solvent, which can create difficulties in applying several coats of 
the same material, especially by brush. Another characteristic is their rapid drying, which, again, can make 
them difficult or impossible to apply by brush to large areas. 
F.2.6 Inorganic (cement and silicate) binders 
F.2.6.1 White Portland cement forms the binding agent in cement paints for use on concrete, brickwork 
and similar surfaces. This type of coating is usually supplied in powder form and mixed with water immediately 
before use. 
F.2.6.2 In continental Europe, silicate-based masonry coatings, based on water-soluble silicate (e.g. 
potassium silicate) have been used for a considerable tune. The coatings form inert, non-flammable films of 
considerable durability. The liquid paint is highly alkaline; hence pigmentation is normally by stable metal 
oxides resulting in a high order of colour stability.  
F.2.6.3 Some specialist coatings for the protection of iron and steel (see ISO 12944 and ISO 14713-1) 
are based on silicates.  
F.2.7 Bituminous binders 
F.2.7.1 Bitumens and tars in solution or as emulsions are used in low-cost coatings, mainly for 
waterproofing. Suitable coal tar fractions are combined with epoxy resins in some specialist coatings (see 
Table 11).  
F.2.7.2 Coatings based on bituminous materials are usually black although, with some types, a limited 
range of dark colours is available. They can also bleed into and discolour other types of coatings applied over 
them (see 8.15). 
F.3 Solvents and thinners 
F.3.1 General 
F.3.1.1 Solvent imparts the appropriate degree of flow, i.e. viscosity, to a paint to facilitate application. 
During the drying process, solvent evaporates and so determines the initial speed of drying. Solvent vapours 
in the atmosphere can give rise to toxicity or flammability hazards (see Annex A).  
F.3.1.2 Coatings are generally supplied ready for use, although further additions of the recommended 
thinner by the user might be permissible, e.g. to assist the penetration of priming coats on absorbent surfaces 
or for application of coatings by spray.   
©RSB 2023- All rights reserved                  136 
 F.3.1.3 Over-thinning can seriously impair the opacity and other properties of coatings, but painting 
specifications need not preclude thinning; as indicated in the previous paragraph, thinning might be necessary 
in some circumstances. The specifications need to state, however, that thinning is to be carried out under 
competent supervision and strictly in accordance with the manufacturer's recommendations as to type and 
proportion of thinner. 
F.3.2 Hydrocarbon solvents 
Hydrocarbon solvents are generally of the white spirit type, although aromatic hydrocarbons such as xylene or 
naphtha might be encountered occasionally. Conventional white spirit contains a mass fraction of about 20% 
of aromatic hydrocarbons, but low aromatic solvents such as de-aromatized white spirit or isoparaffins are 
increasingly used. As well as having low odour, these solvents are considered to be less harmful. 
F.3.3 Oxygenated solvents 
Oxygenated solvents are derived from organic chemicals and small quantities might be included for specific 
purposes, e.g. help film formation in some water-borne paints. They are a major constituent of cellulose-based 
paints and knotting solutions (see 7.4.3), and are also used in two-pack epoxy and polyurethane paints. 
F.3.4 Water 
Water-borne paints and bituminous emulsions are thinned using water. However, many water-borne paints 
contain some oxygenated solvent to give good low temperature film formation. 
F.4 Pigments 
F.4.1 General 
F.4.1.1 The major function of the pigment is to provide colour and opacity. Additionally, and according to 
the nature of the pigments used, they can increase the thickness of the dry film, reinforce it physically, absorb 
or reflect harmful ultraviolet radiation, inhibit corrosion on metal surfaces or otherwise contribute to the 
durability or stability of the coating.  
F.4.1.2 A wide variety of pigments, differing in origin, colour and properties, are available. The principal 
categories are described in F.4.2 to F.4.6. 
F.4.2 White pigments 
Because of the preponderant use of white and light-coloured finishes, white pigments are of considerable 
importance in the manufacture of paint. Titanium dioxide is the most widely used white pigment; it is non-toxic, 
has colour and opacity and is resistant to discoloration.  
NOTE The use of white lead is restricted to use by specialists for the maintenance of listed historic buildings. DRS 554: 2022 
137                ©RSB2023- All rights reserved 
 F.4.3 Tinting pigments 
F.4.3.1 Tinting pigments comprise pigments that are used primarily for their colour when used alone or as 
tinters in combination with white, although some can have other properties. The main pigments in this 
category are natural or synthetic metal oxides, organic pigment dyestuffs and carbon black.  
F.4.3.2 Coloured pigments vary considerably in properties and, in particular, in opacity. Some dyestuff 
pigments are relatively low in opacity and, with strongly coloured coatings based on pigments of this type, 
additional coats might be required (see Annex G). 
F.4.4 Extenders 
Extenders are inert materials, usually of mineral origin. Although generally classed as pigments, they might 
contribute little to the opacity of coatings but perform other useful functions such as reinforcing the mechanical 
strength of the dry film; assisting application; imparting bulk or structure to the liquid paint and helping to 
prevent settlement of the solid ingredients during storage; improving intercoat adhesion or imparting 
roughness or texture to the coating when this is required. 
F.4.5 Corrosion-inhibitive pigments 
F.4.5.1 Corrosion-inhibitive pigments inhibit or retard the corrosion of ferrous and non-ferrous metals and 
are used in primers for these surfaces. They include metallic zinc and zinc phosphate.  
F.4.5.2 The properties of an inhibitive pigment can be influenced by the nature of the medium in which it 
is used. Metallic zinc is generally used in conjunction with oil-free binders of the solution or chemically- curing 
type, e.g. those based on chlorinated rubber or epoxy resin.  
NOTE Red iron oxide (red oxide), although having no inhibitive properties, is often used in conjunction with inhibitive pigments as a 
colouring agent. Due to their toxicity, lead and chromate pigments have a restricted range of uses. 
F.4.6 Laminar pigments 
Laminar pigments have a flaky structure and, within the paint film, the individual flakes lie parallel to the 
surface and overlap, forming a moisture barrier and improving tensile strength. Widely used pigments of this 
type include micaceous iron oxide (MIO), aluminium and graphite. The two latter pigments, in addition to their 
general use in protective coatings, are also used in heat-resisting paints.  
©RSB 2023- All rights reserved                  138 
 Annex G 
(informative)  
 
Paint colours 
G.1 The available pigments make possible a very wide range of colours although, in practice, the number of 
standard paint colours produced is restricted by economic considerations and, in some cases, by technical 
limitations. Paint manufacturers issue cards showing the standard colours in which their products are 
available. Some colours might be unsuitable for exterior use, and the manufacturer's recommendations on this 
aspect need to be followed.  
G.2 BS 4800 is a range of colours for building paints, derived from BS 5252, which establishes a framework 
within which a number (237) of colours have been selected as the source for all building colour standards and 
the means of co-ordinating them. Most paint manufacturers supply the full range of BS 4800 colours although 
not necessarily in all types of paints or from stock.  
G.3 A useful function of paint is as a means of identifying the nature of piped services and the location of 
safety appliances by colour codes. BS 1710 and BS 5378-2 give details of this application.  
G.4 House colours are used by many large organizations to give corporate identity to buildings, equipment, 
vehicles, etc. Many standard colours of this nature used by official bodies are embodied in BS 381C.  
G.5 Texture influences the appearance of colours, and only to an approximate degree can a gloss colour be 
matched with that of a textured fabric. For accurate matching of colour, specimen and sample ought to be of 
the same finish and texture. Larger specimens than those normally given in colour cards need to be used for 
matching. Manufacturers might issue swatch books suitable for this purpose, and separate large cards of BS 
4800 colours are available from the British Standards Institution.  
G.6 Colours alter in drying: therefore, comparisons of colour in paint cannot be made until sample and 
match are both dry. The sample and the colour match made to it needs to be viewed in several forms of light, 
natural and artificial, since many pah's of colours which match in one illuminant appear to be quite different in 
colour in another. This effect is known as metamerism and usually derives from the choice of different pigment 
combinations used to prepare the comparison standard and the colour match.  
G.7 It is important when purchasing paint, that where ever possible different containers have the same 
batch numbers. Slight variations in colour could occur between different batches of paint which will be 
noticeable if the products are used in juxtaposition. If batching is not possible then different containers should 
either be intermixed in a larger vessel or individual batches used to complete whole separate elevations.  
G.8 Coloured pigments vary considerably in opacity, and, with many strong colours, especially those 
employing dyestuff pigments, special undercoats or additional finishing coats might be needed in order to 
achieve satisfactory appearance. The manufacturer's recommendations in this respect need to be followed 
and, where necessary, the use of special undercoats or additional finishing needs to be covered in the 
painting specification. DRS 554: 2022 
139                ©RSB2023- All rights reserved 
 Annex H 
(informative)  
 
Iron and steel 
H.1 Characteristics 
H.1.1 Most forms of iron and steel, if not protected, tend to revert to their oxides by gradual combination with 
oxygen and moisture to form rust. In clean atmospheres, significant corrosion is unlikely unless the relative 
humidity exceeds about 70% but, if there are sulfur compounds or other soluble salts (e.g. sea salt) in the 
atmosphere or on the surface, severe corrosion can occur at lower levels of relative humidity. Corrosion is 
likely to be more severe in humid industrial areas and near the coast rather than in rural or urban areas.  
H.1.2 The micro-climate and factors such as orientation, degree of exposure and the flow of air over the 
surfaces, immediately surrounding the structure or component can increase or reduce the rate of corrosion. 
The frequency and extent to which condensation occurs, as a result of the difference in temperature between 
the metal and the air can also be relevant; in this respect, the thickness of the metal can be a significant 
factor. 
H.2 Cast iron 
The scale formed on cast iron is more adherent than the millscale on mild steel and has some protective 
value. If the scale is removed, cast iron corrodes at about the same rate as mild steel. This might not be 
immediately apparent because the corrosion process leaves behind a non-metallic residue which largely 
retains the appearance of the original metal although its mechanical strength is negligible. 
H.3 Wrought iron 
In respect of painting, this is similar in characteristics to mild steel although its corrosion rate might differ 
slightly according to its composition.  
©RSB 2023- All rights reserved                  140 
 Annex I 
(informative)  
 
Plaster 
I.1 General 
I.1.1 BS 1191-1 distinguishes four grades of gypsum plasters only two of which are in common usage: 
Grade A. Plaster of Paris. This is not normally used for plastering but is sometimes used for repairs and might 
be gauged with lime or lime and sand. For painting purposes, it might be considered with grade B.  
I.1.2 Grade B. Retarded hemi-hydrate plasters. These have a smooth, hard but moderately porous surface 
to which paint adhesion is good, but absorption is sometimes variable and can cause patchiness of water-
borne paints.  
I.1.3 Grade B plasters are generally neutral in reaction and, even if gauged with lime, should not affect 
paint unless there is a source of alkali in the backing. Over-wetting during application can produce a powdery 
surface. In damp conditions (e.g. from prolonged heavy condensation or moisture penetration from behind), 
sweat out can occur, resulting in softening of the plaster and consequent paint failure. 
I.2 Lightweight plasters 
I.2.1 BS 1191-2 describes lightweight gypsum undercoat and finish plasters based on grade B plasters with 
lightweight aggregates. Their general characteristics, in relation to painting, are as described in 8.6.1.2. 
Premixed lightweight cement plaster undercoats can be used in some circumstances, and these are strongly 
alkaline.  
I.2.2 Lightweight plasters initially hold more water than other types and can take longer to dry out 
particularly in winter. DRS 554: 2022 
141                ©RSB2023- All rights reserved 
 Annex J 
(informative)  
 
Paper and wallcoverings 
J.1 General 
J.1.1 Papers and other wallcoverings comprise, first, those that are supplied uncoloured and that are 
intended to be painted and, secondly, existing coloured materials that might be suitable for painting in order 
that their appearance might be restored or that their colour might be changed. The mam types in each 
category are as follows:  
a) new and intended to be painted:  
1) lining papers;  
2) woodchip papers;  
3) relief wallcoverings;  
4) natural hessians (painting optional);  
5) blown vinyl wallcoverings;  
6) non-woven backed wallcoverings;  
7) woven glass fibre paper.  
b) existing coloured materials:  
1) wallpapers;  
2) ii) paper-backed and sheet vinyls;  
3) iii) coloured hessians;  
4) iv) non-woven backed wallcoverings.  
J.1.2 No problems arise with materials in the first category in respect of painting, but problems can be 
experienced with some of those in the second category, as indicated in 8.12.1.2 and 8.12.1.3.  
©RSB 2023- All rights reserved                  142 
 J.2 Plasterboard 
Plasterboard consists of a core of gypsum plaster with a thick paper liner on each side. Plasterboard can be 
skimmed with plaster after fixing, the surface then being painted as described for plaster in 8.6. It is also 
widely used in dry-lining systems in which paint or wallcoverings are applied directly to the board surface after 
fixing. Dry-lining systems usually involve special treatment of the joints between the boards. DRS 554: 2022 
143                ©RSB2023- All rights reserved 
 Annex K 
(informative)  
 
Bricks, stone and concrete blocks 
K.1 Bricks and stone 
K.1.1 Clay bricks 
Most clay bricks contain soluble salts and these, in combination with water and the alkalis in cement mortars, 
can promote efflorescence (see 8.5.1.2). Clay bricks can be classified in general terms, by type, as common, 
facing and engineering bricks.  
a) Common bricks. These are usually plastered or rendered, but painting can be considered as a low-cost 
alternative especially for interior walls. Paints of all types are liable to failure by loss of adhesion when 
applied to Fletton common bricks externally. Failure occurs initially over kiss marks in the bricks, often 
within two years, and increases progressively; after four or five years, the paint on the whole of the brick 
surfaces can be affected. Sand-faced and rustic Flettons are not subject to paint adhesion failures to any 
great extent. BRE Information Paper 22/79, Difficulties in painting Fletton Bricks [40], recommends that 
external walls built with the intention of painting be of either sand-faced or rustic clay bricks or of calcium 
silicate or concrete bricks. It also gives recommendations for alternative treatments in situations where the 
extent of paint failure on walls already painted makes it not worth attempting to maintain them in the 
painted state.  
b) Facing bricks. These are made or selected for their appearance, e.g. colour or texture. Adhesion of paint 
is usually satisfactory.  
c) Engineering bricks. These are dense, strong bricks made to defined limits of strength and water 
absorption. The adhesion of paints of conventional type to the virtually non-porous surface of bricks of this 
type is generally poor and, if painting is necessary, paints of the types recommended for glazed bricks 
(see 8.14.2) needs to be used. 
K.1.2 Calcium silicate (sandlime or flintlime) bricks 
The surface of calcium silicate bricks is usually smoother than that of clay bricks although textured facing 
bricks are available. Paint adhesion is generally satisfactory. 
K.1.3 Concrete bricks 
Concrete bricks are strongly alkaline. 
K.1.4 Stone 
The many varieties of natural stone differ considerably in hardness and porosity, e.g. from virtually non-porous 
granite or marble to porous limestone or sandstone. There might also be differences in surface texture 
according to the method by which the stone is dressed or finished.  
©RSB 2023- All rights reserved                  144 
 K.2 Concrete blocks 
K.2.1 Precast concrete blocks are described in BS 6073-1 and BS EN 772-2. Their essential constituents 
are cement (usually ordinary or rapid-hardening Portland cement), a wide variety of aggregates and water. 
The main types of blocks are as follows.  
a) Aerated concrete blocks are usually made from mixtures of cement and siliceous materials, such as sand 
or pulverized fuel ash or a mixture of these, together with an aerating agent.  
b) Dense and lightweight blocks are made from cement and dense or lightweight aggregates, moulded and 
compacted by vibration or pressure.  
K.2.2 The aggregates used and the manufacturing process employed affects the physical properties, 
surface texture and colour of the blocks. Surfaces can vary from coarse and open to fairly smooth and fine-
textured. Colour is derived from the aggregates used, but pigments can be incorporated. Blocks are also 
available with a factory-applied coloured glaze that is resistant to staining and chemical attack.  
K.2.3 Provided that types having the appropriate properties are selected, concrete blocks are durable in 
most internal and external situations and are normally painted for aesthetic reasons or to facilitate cleaning. 
However, painting protection might be required where blockwork is exposed to severe driving rain. The natural 
appearance of some blocks might be acceptable without further treatment although clear coatings can be 
used to prevent staining or soiling. 
K.3 Cement-based sheets, boards and components 
K.3.1 General 
The sheets, boards and components to which this clause refers are manufactured from cementitious materials 
reinforced with fibres. They comprise:  
a) asbestos and fibre-cement goods;  
b) cement-based insulating boards, ceiling tiles and planks;  
c) glass fibre reinforced cement (GRC) cladding. 
K.3.2 Asbestos and fibre-cement goods 
WARNING! Materials containing asbestos are subject to the legislation that requires precautions to be taken in handling them to ensure 
that they do not constitute a hazard to health (see K.3.3 and Annex B). 
K.3.2.1 Asbestos and fibre-cement goods include roofing and cladding materials, lining sheets, decking 
tiles, rainwater goods and other components. They are manufactured from Portland cement (CEM 1), 
asbestos or other fibre and water, compressed to a fairly high density.  
K.3.2.2 Asbestos-cement is a reasonably durable material, resistant to most forms of attack, and does not 
require painting for protection except in highly acidic atmospheres. In other situations, painting is mainly for DRS 554: 2022 
145                ©RSB2023- All rights reserved 
 appearance, to facilitate cleaning or to seal degraded surfaces to prevent loss of fibres. Asbestos-cement 
sheets and components supplied with factory-applied coatings have good chemical resistance.  
K.3.2.3 Fibre-cement shares many of the properties associated with asbestos-cement.  
K.3.2.4 Asbestos and fibre-cement is strongly alkaline when new and, if it is damp when painted or 
becomes so later, paints susceptible to alkaline attack (see 8.5.1.4) are affected.  
K.3.2.5 If impermeable paint systems are applied to one side only of flat sheets or profiled sheets with 
large flat areas, differential carbonation can cause distortion and cracking of the sheets. This can be 
prevented by back-painting the sheets (see 8.11.1.4). 
K.3.3 Cement-based insulating boards, tiles and planks 
Cement-based insulating boards, tiles and planks can be made from Portland cement (GEM 1) and asbestos 
fibre, glass and other fibres (superseding asbestos, which might still be found in older material). Calcium 
silicate can also replace Portland cement (CEM 1) in some types.  
Cement-based insulating materials are less dense and more porous than asbestos and fibre-cement goods 
and are used principally as internal wall and ceiling linings. In the situations in which they are normally used, 
painting is essentially for appearance and to facilitate cleaning. 
The materials, especially the types employing calcium silicate as a binder, are usually less alkaline than 
asbestos- and fibre-cement goods. Differential carbonation (see 8.11.1.44) is not a problem, and back-
painting is not therefore necessary.  
WARNING! Cement-based insulating materials containing asbestos fibre constitute a serious hazard to health and if found, should not 
be disturbed. Unknown cement-based insulating materials should be treated as containing asbestos fibre until properly identified. 
Specialist advice should be sought on the treatment of all asbestos containing materials and if necessary the correct method for its safe 
removal and disposal. 
K.3.4 Glass fibre reinforced concrete (GRC) components 
Most GRC consists of Portland cement (CEM 1) matrix reinforced with glass fibre. There are a variety of GRC 
components, a major use being in sheets and composite cladding panels, many with a factory-applied coating. 
The general requirements for site painting are as for other cement-based products.  
©RSB 2023- All rights reserved                  146 
 Annex L 
(informative)  
 
Conditions of application  (temperature and humidity) 
L.1 The initial stage in the drying of most coatings is dependent, in varying degree, on the evaporation of 
solvent or thinner. Evaporation is slower in conditions of low temperature or high humidity, with a 
corresponding effect on the drying rate. In very hot conditions, the rate of evaporation can be so rapid as to 
cause difficulty in maintaining a wet edge (see 9.3.2.3). 
L.2 Solvent-borne coatings, especially gloss finishes, tend to become thicker and more difficult to apply at 
low temperatures, and this can result in the application of excessively thick films which through- harden slowly 
or develop surface defects such as sagging or rivelling (wrinkling). High temperatures cause solvent-borne 
coatings to become thinner, and this can result in the application of excessively thin films.  
L.3 The drying of water-borne coatings depend almost entirely on evaporation of the water content and in 
highly humid conditions can be very slow, causing the coating to run or sag. With water-borne paints, 
formation of a homogeneous film, after evaporation of the water, depends upon coalescence of the polymer 
particles. This can be inhibited at low temperatures, resulting in permanent impairment of film properties, 
notably washability and film strength.  
L.4 With two-pack epoxy, polyurethane and similar types of coatings, there is a secondary curing stage in 
which the full properties of the coating, e.g. of chemical resistance, are developed and this stage is 
temperature-dependent. There might be a lower temperature limit below which application is not 
recommended. The pot-life of two-pack coatings, i.e. the period during which they are usable, is also 
temperature-dependent, becoming shorter as temperature increases.  
L.5 Seasonal variations in temperature, humidity and general weather conditions can impose constraints on 
the application of coatings, especially on external work. It is generally accepted that the optimum period for 
external painting in Great Britain is from mid-April to mid-September. However, the climate is sufficiently 
variable, geographically and from year to year, for there to be frequent exceptions.  
L.6 Conditions are not always favourable during the period indicated, while there are other occasions during 
the remainder of the year when external painting could proceed without difficulty or detriment to the properties 
of coatings. Confining external painting strictly to the period traditionally regarded as most suitable can often 
be unduly restrictive. 
 
 
 DRS 554: 2022 
147                ©RSB2023- All rights reserved 
 Bibliography 
[1] ISO/IEC Directives, Part 2, Rules for the structure and drafting of International Standards , 2016 
[2] ISO/IEC TR 10000-1, Information technology— Framework and taxonomy of International 
Standardized Profiles— Part 1: General principles and documentation framework 
 
 DRS 554: 2023 
 
Price based on  nnn pages 
©RSB2023- All rights reserved