ICS 79.040  
 
Reference number  
DRS 435: 2019  
© RSB 2019  
  
 RWANDA 
STANDARD  DRS 
435  
 
1st edition  
2019 -11-dd 
 
Timber in joinery — General requirements  
   
DRS 435:2019  
©RSB 2019  - 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  
 
 
 
 
 
 
 
 
© RSB 2019  
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 R SB. 
Requests for permission to reprodu ce 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.rs b.gov.rw  
ePortal: www.portal.rsb.gov.rw   DRS 435:2019  
iii                ©RSB 2019  - All rights reserved  
 Contents  Page 
Foreword  ................................ ................................ ................................ ................................ ...................  iv 
1 Scope  ................................ ................................ ................................ ................................ .............  1 
2 Normative references  ................................ ................................ ................................ ...................  1 
3 Terms and definitions  ................................ ................................ ................................ ..................  1 
4 Basic principles for classification of timber used in joinery  ................................ ...................  2 
4.1 Appearance classes  ................................ ................................ ................................ .....................  2 
4.2 Species  ................................ ................................ ................................ ................................ ..........  2 
4.3 Density  ................................ ................................ ................................ ................................ ...........  3 
4.4 Surface quality  ................................ ................................ ................................ ..............................  3 
4.5 Moisture content  ................................ ................................ ................................ ...........................  3 
4.6 Finger -jointing, butt -jointing, edge -jointing and laminating  ................................ ....................  3 
5 Classification of features  ................................ ................................ ................................ .............  3 
5.1 Knots and knot clusters ................................ ................................ ................................ ...............  4 
5.1.1  Types  ................................ ................................ ................................ ................................ .............  4 
5.1.2  Size................................ ................................ ................................ ................................ .................  4 
5.1.3  Distribution  ................................ ................................ ................................ ................................ ... 5 
6 Remedial work  ................................ ................................ ................................ ..............................  5 
6.1 Plugs and fillers  ................................ ................................ ................................ ............................  5 
6.2 Requirem ents ................................ ................................ ................................ ................................  5 
Annex  A (normative)  Annex Guide to specifying timber in joinery ................................ .....................  8 
A.1 Information to be supplied  ................................ ................................ ................................ ..........  8 
A.2 Identifying characteristics, techniques or remedies and their acceptability with visible 
surfaces  ................................ ................................ ................................ ................................ .........  8 
 DRS 435:2019  
©RSB 2019  - All rights reserved                  iv 
 Foreword  
Rwanda Standard s are prepared  by Technical Committees and approved by R wanda 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 o f technical committees is to prepare national standards.  Final Draft Rwanda S tandards adopted 
by Technical committ ees are ratified  by me mbers of RSB Board of Director s for publication and gazettment as 
Rwanda Standards.  
DRS 435 was prepared by Technical Committee RSB/TC 54, Timber, furniture and engineered wood . 
Committee membership  
The following organizations were represented on the Technical Committee on Timber, furniture and engineered 
wood of RSB/TC 54 in the preparation of this standard.  
Action pour le Development de l`Artisanat au Rwanda (ADARWA)  
Association pour la défense des droits des consommateurs au Rwanda  (ADECOR)  
Association pour la Promotion des Artisans du Bois (APROAB)  
GIZ Eco — Emploi  
Integrated Polytechnic Regional Centre (IPRC) Kitabi  
Kalka and Partners Ltd  
Manumetal Ltd  
Mass Design Ltd  
Ministry of Trade and Industry (MINICOM)  
National Industrial Research and Development Agency (NIRDA)  
New Forest Company (NFC) Ltd  
REAL Contractors Ltd  
Rwanda Education Board (REB)  
Rwanda Environment Management Authority (REMA)  DRS 435:2019  
v                ©RSB 2019  - All rights reserved  
 Rwanda Public Procurement Authority (RPPA)  
Rwanda Water and Forestry Authority (RWFA)  
Straw Tech Building Solutions  
University of Rwanda – College of Agriculture, Animal Sciences and Veterinary Medecine (UR – CAVM)  
University of Rwanda – College of Science and Technology (UR – CST)  
Rwanda Wood Value Chain Association/Private Sector Federation (WVCA/PSF)  
Rwanda Standards Board (RSB) – Secretariat  DRS 435:2019  
©RSB 2019  - All rights reserved                  vi 
 Introduction  
Despite the Rwandan growth trend, the wood sector has not been implemented as required to produce high 
quality wood products and vigorous competitive market. The quality of wooden furniture is highly affected by 
the quality of timber, standardized production chain, quality co ntrol mechanism and grading rules. The lack of 
aforesaid factors results into market dominated by poor quality wooden furniture, compromised safety and unfair 
competition at the market.  
The emerging market dynamics show that consumer’s preferences have gra dually shifted from furniture made 
by local timbers to the imported ones, which is considered as a limiting factor to the development and growth of 
the wood economy in Rwanda.  
To ensure a positive trade balance in wood market there is a dire need to improv e and ensure quality of domestic 
wood products. One of the solutions to the aforesaid challenges is to put in place standards which will guide the 
wooden products manufacturers.  
This Standard is one of a series prepared on timber in Rwanda. The series curr ently consists of the following:  
DRS 433  Furniture – Chairs and tables for home furniture - Functional sizes a nd performance requirements  
DRS 434  Furniture - Tables - Test methods for the determination of sta bility, strength and durability  
DRS 435  Timber in  joinery — General requirements  
FDRS   413  Furniture — Quality and grading of wooden furniture  
FDRS 423  Furniture – Chairs and tables for office furniture – Functional sizes and performance requ irements  
FDRS 424  Furniture  – Specifications for bedsteads  
FDRS 425  Furniture – Storage units - Functional sizes, stability, strength a nd durability  
FDRS 426  Furniture - Chairs and tables for educational institutions - Functional sizes and performan ce 
requirements  
FDRS 427  Round and sawn timber – Nomenclatur e of timbers used in RwandaDRS 435:2019  
1                ©RSB 2019  - All rights reserved  
 Timber in joinery — General requirements  
1 Scop e 
This standard specifies the general requirements including in particular the grading and classification by 
appearance quality of timber in joinery products or individual joinery par ts. 
This Standard covers solid, finger -jointed, end -jointed, edge -jointed and laminated timber products.  
This Standard is intended to be used at the time of manufacture of a product.  
This Standard may be used also to evaluate products at a later stage, but in these situations storage and service 
conditions, subsequent to manufacture, shall be taken into account (surface checks).  
Matters relating to the influence of timber characterist ics on strength and durability are not covered in this 
standard.  
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 edition  cited applies. For undated references, the 
latest edition of the referenced document (including any amendments) applies.  
RS EAS 24:2000, Timber industry – Glossary of terms  
RS ISO 24294, Timber — Round and sawn timbe r —Vocabulary  
3 Terms and definitions  
For the purposes of this standard , the terms and definitions given in RS EAS 24: 2000, RS ISO 24294  and the 
following apply.  
3.1 
joinery  
Wood and wood -based products graded for non -structural use within a building  
3.2  
concealed face   
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 face of a joinery part which, after installation of the joinery is completed, is permanently concealed by other 
parts of the joinery product, by other parts or by other elements including sheet materials such as veneer, solid 
plastic or meta l 
3.3 
visible face  
face of a joinery part which, after installation of the joinery is completed, is not permanently concealed or semi 
concealed  
3.4 
plug 
piece of wood used to stop up a hole, an aperture or to fill a gap or to act as a wedge  
3.5 
filler  
semisolid material that hardens on drying, used to  fill pores, cracks, or holes in wooden  surfaces before finishing  
4 Basic principles for classification of timber used in joinery  
4.1 Appearance classes  
Timber in joinery shall be classified by referencing a number of basic features which are given in Clause 5 and 
summarised in Table 1. In addition, a number of other factors shall be taken into account and these are given 
in the rest of Clause 4.  
Any feature is accepted on a concealed face if the serviceabilit y of the product is not impaired.  
4.2 Species  
Timber species used in joinery shall be suitable for its intended purpose. In high grades furniture, renown  timber 
selected based on colour, figure, stability, ease of working and good finishing properties  shall be used . In 
cheaper grades  furniture, use shall  be made of poorer quality timber provided it is stable in service and free 
from visible defects . 
Note 1: Renown timber species used for high grade in joinery include Pterocarpus angolensis , Khaya antho theca , 
Entendrophragma excelsum , Entendrophragma utile , Entendrophragma cylindricum , Albizia gummifera , Acacia 
melanoxylon , Markhamia lutea  and Juniperus procera . 
Note 2: Timber species used in cheaper grades furniture include Acacia abyssinica , Macaranga neomildbraediana , 
Maesopsis eminii, Hagenia abyssinica  and Newtonia buchananii .  DRS 435:2019  
3                ©RSB 2019  - All rights reserved  
 4.3 Density  
The density of timber used will have a significant effect on mechanical performances. Timber species used in 
joinery shall have a density of at least 400 kg/m3. 
4.4 Surface quality  
The surface of timber in visible faces shall be able to accept a coating system without any further operation 
other than light sanding.  
4.5 Moisture content  
The moisture content (percent) of the timber used in joinery shall be between 12% and 1 9%. The final moisture 
shall be agreed between two parties provided that it falls in the specified range.  
4.6 Finger -jointing, butt -jointing, edge -jointing and laminating  
Unless otherwise agreed, finger -jointing, butt -jointing and edge -jointing shall be permit ted in classes C to G 
according to Table 1 but shall not be permitted in class A and B, unless accepted by a product standard.  
The distance between the centres of finger -joints and butt -joints shall be at least 150 mm.  
Laminating sections in any class shal l be permitted unless otherwise agreed between two parties.  
5 Classification of features  
The appearance classes in Table 1 are independent of the species. The limits set in Table 1 for each feature 
relative to the specific class shall not be exceeded when a specific class is specified. The classification of 
features can be missed subject to the declaration of the class for each feature as given in Annex B . 
Table 1 shows where and to what extent the presence of the following features shall be permitted at the time of 
handover, for the various classes of timber.  
NOTE 1 Handover relates to the time the joinery is supplied by the manufacturer to the first purchaser.  
The following features are identified in Table 1:  
 Spiral grain;  
 Slope of grain;  
 Loose or unsound knots;  
 Knots;  
 Resin pockets;   
©RSB 2019  - All rights reserved                  4 
  Bark pockets;  
 Fissures, shakes;  
 Exposed pith;  
 Discoloured sapwood;  
 Ambrosia beetle damage.  
Where remedial work on the part of the manufacturer is permitted in Table 1, it shall be carried out in accordance 
with clause 6.  
The following features are generally not permitted:  
 Reaction wood;  
 Splits;  
 Biological attack;  
 Wane.  
5.1 Knots and knot clusters  
5.1.1  Types  
Knots and knot clusters shall be limited in size and distribution, according to 5.2.2 and 5.2.3. Loose or unsound 
knots shall not  be present except on concealed faces. When they occur on a visible face, the timber shall be 
repaired in accordance with clause 6. Arris knots shall comply with the requirements of both faces on which 
they appear.  
NOTE Arris knots may be impossible to rep air unless extremely sound.  
5.1.2  Size 
Unless otherwise specified in the relevant product standard or specification, the limit on size shall be expressed 
as a percentage of the overall width or thickness of the finished piece on which the knot or knot cluster o ccurs 
and a maximum knot size.  
No individual knot or knot cluster shall exceed the size limit shown in Table 1, as appropriate for:  
a) Class of timber;  
b) Face category (visible, semi -concealed or concealed).  DRS 435:2019  
5                ©RSB 2019  - All rights reserved  
 These size limits apply even if a piece of timber is laminated or edge jointed.  
5.1.3  Distribution  
On visible faces, knots or knot clusters larger than 10 mm shall be distributed at centres no closer than 150 mm 
on average, measured over the length of the piece.  
For all classes, when considering distribu tion, knots of 10 mm or less shall be disregarded.  
6 Remedial work  
6.1 Plugs and fillers  
Where indicated in Table 1, the following shall be repaired by the manufacturer with a plug or filler:  
 Loose or unsound knots;  
 Shakes greater than 0,5 mm in width;  
 Resin po ckets;  
 Bark pockets;  
 Exposed pith;  
 Ambrosia beetle attack.  
NOTE It is impractical to fill shakes narrower than 0,5 mm.  
Repair to visible faces in A  and B classes according to Table 1 is not permitted, remedial work to semi -concealed 
faces of A and B is acceptable.  
6.2 Requirements  
Any plug shall:  
a) Be of the same or similar species as the surrounding timber;  
b) Be well secured by an appropriate adhesive;  
c) Have the moisture content similar to the surrounding timber;  
d) Occupy the depth of the hole whenever  possible;   
©RSB 2019  - All rights reserved                  6 
 e) Whenever possible lie with its grain in the same general direction as the grain of the piece into which it is 
inserted;  
f) Be of a dimension not greater than 6 mm above the maximum limit of knot size for the specified class; (the 
width of a n on-cylindrical plug shall be not more than 30 mm);  
g) Have at least 2/3 of its diameter within the face when occurring at an arris;  
i) Have a wood density similar to the surrounding timber species.  
In the case of an abnormally elongated knot or defect not more than two plugs shall be used. Not more than 
one plug shall be used for a single repair below a translucent coating.  
NOTE 1 The intersecting of plugs is permitted.  
NOTE 2 A plug need not necessarily be cylindrical.  
The repair of a knot shall be classif ied as a sound inter -grown knot.  
Where surfaces or defects are required to be filled the filler shall be compatible with the end use of the timber 
and shall completely fill the hole or shake. Fillers used in weather exposed faces shall be weather -resistant . 
NOTE 4 Consideration should be given to the compatibility of a filler with any applied coating.  
Table 1— Limits of timber features according to class and face  
Features  Classes  
    A B C D E F G 
1 
Spiral grain  Not 
permitted  Not 
permitted  ≤ 10 mm/m  ≤ 10 mm/m  ≤ 10 mm/m  ≤ 20 mm/m  ≤ 20 mm/m  
2 Slope of 
grainc ≤ 20 mm/m  ≤ 20 mm/m  ≤ 50 mm/m  ≤ 50 mm/m  ≤ 50 mm/m  ≤ 100 
mm/m  No limit  
3 Knotsa               
Max % of the 
face or  10 20 30 30 30 40 50 
max. 
diameter  2 mm  5 mm  10 mm  20 mm  30 mm  40 mm  50 mm  
4 Resin 
pockets, 
bark 
pockets(if 
more than 
one per 
metre total 
length shall 
not exceed 
length given 
for class)  Not 
permitted  ≤ 3 mm x 
30 mm per 
2 m length  ≤ 3 mm x 
75 mm per 
2 m length  ≤ 3 mm x 
75 mm per 
2 m length  ≤ 3 mm in 
width         
No limits is  
applied to  
length  ≤ 3 mm in 
width No 
limits is  
applied to  
length  ≤ 3 mm in 
width No 
limits is  
applied to  
length  
5 Fissures, 
shakes  Not 
permitted  Not 
permitted            
Max. width  0.5 mm  0.5 mm  1.5 mm  1.5mm  1.5mm  DRS 435:2019  
7                ©RSB 2019  - All rights reserved  
 Max. 
individual 
length of 
fissure  50 mm  50 mm  200 mm  300 mm  300 mm  
Max. 
aggregate 
length of 
fissures as a 
percentage 
of the length 
of each face  10% 10% 25% 50% 50% 
6 
Exposed pith  Not 
permitted  Not 
permitted  Not 
permitted  Not 
permitted  Permitted  Permitted  Permitted  
7 Discoloured 
sapwood 
(inc.blue 
stain )b Not 
permitted  Not 
permitted  Not 
permitted  Not 
permitted  Permitted 
if repaired  Permitted 
if repaired  Permitted if 
repaired  
8 Ambrosia 
beetle 
damage  Not 
permitted  Not 
permitted  Permitted 
if repaired  Permitted 
if repaired  Permitted 
if repaired  Permitted 
if repaired  Permitted if 
repaired  
a The limit on knot size is expressed as a percentage of the overall width or thickness of piece on which the knot or 
knot cluster occurs subject to a maximum knot size expressed in mm.                                                                                                                              
b In classes J30 -J50 blue stain may be concealed by the application of a specific treatment (e.g. lightly coloured 
varnish).       
c Slope of grain is measured in an undisturbed area.  
NOTE  Any feature  is accepted on a concealed face if the serviceability of the product is not impaired.  
Table 1 sets limits for each feature relative to the specific class declared. These limits shall not be exceeded 
when a specific class is specified. For example, for Cl ass D criteria D1 to D8 shall not be exceeded.  
Where the same class is not required for each relevant feature , the manufacturer shall declare the difference 
using Annex B by  filling in all relevant fields.   
©RSB 2019  - All rights reserved                  8 
 Annex  A 
(normative)  
 
Annex  Guide to specifying timber in joinery  
A.1 Information to be supplied  
The following should be stipulated:  
a. Local, common and scientific names of the species required;  
b. Required class or classes of timber according to Table 1, taken from the choices offered;  
c. Required moisture content  
d. Purpose for which the joinery is intended when installed;  
e. Finishes used/to be used  
A.2 Identifying characteristics, techniques or remedies and their acceptability with  
visible surfaces  
Where it is intended that joinery will have a visible surface, it should be conside red whether any of the following 
are unacceptable.  
a. The use of:  
1. Laminating without end or finger jointing in the laminations;  
2. Laminating with end or finger jointing in the laminations;  
3. Finger -jointing of solid sections;  
4. Edge -jointing.  
 
b. The use of remedial work where the following natural features occur:  
1. Loose or unsound knots;  
2. Shakes;  
3. Resin pockets or bark pockets;  
4. Exposed pith;  
5. Damage arising from ambrosia beetle attack.  
c. Discoloured sapwood.  
d. Timber with areas of high absorption.  
Where some species are to be finished with a decorative stain or varnish, it is necessary to specify that there 
should be no significant surface area of high porosity.   
 
 
 
 DRS 435:2019  
9                ©RSB 2019  - All rights reserved  
 Annex  B 
(normative)  
 
Template for timber grading for a particular product  
B.1 Template for timber grading for a particular product  
 Types of product      
 Product standard  No Yes RS xx  
 Timber species      
 Minimum Density kg/m3     
 Moisture content      
  Classes as described in Table 1  
 Features  Visible 
face Semi -
concealed  
face c Concealed face c  Product standard 
– 
 Classes/  
requirements  
1 Spiral grain      
2 Slope of grain      
3 Knotsa 
Max % of the face or  max. 
diameter      
4 Resin pockets, bark pockets 
(if more than one per metre 
total length shall be not 
exceed length given for 
class)      
5 Fissures, shakes  
Max. width  
Max. individual length of 
fissure  
Max. aggregate length of 
fissures as a percentage of 
the length of each face      
6 Exposed pith      
7 Discoloured sapwood (incl. 
blue stain)b      
8 Ambrosia beetle damage      
 Additional characteristics  
Acceptable/non 
acceptable      
9 Sapwood       
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 10 Growth ring      
11 Finger jointing      
12 End jointing      
13 Edge jointing      
14 Laminating      
a The limit on knot size is expressed as a percentage of the overall width or thickness of the piece on 
which the knot or knot cluster occurs (see Annex A) subject to a maximum knot size expressed in mm.  
b In classes E to G  blue stain may be concealed by the application of a specific treatment (e.g. lightly 
coloured varnish).  
c Unless otherwise indicated, semi -concealed face in the same product may be graded to one class lower 
and concealed faces may be any class.  
NOTE  Any feature is accepted on a concealed face if the serviceability of the product is not impaired.  
B.2 Example of  a template filled in by a manufacturer  
 Types of product  Ceiling timber cladding  
 Product standard  No Yes RS Number  N/a 
 Timber species  Markhamia lutea  
 Minimum Density kg/m3     
 Moisture content  15 %  
  Classes as described in Table 1  
 Features  Visible face  Semi -
concealed  
face c Concealed face c  Product standard 
– 
Classes/requireme
nts (as per table 1)  
1 Spiral grain  D(D1)*  D (D1)  F(F1)   
2 Slope of grain  D (D2)     
3 Knotsa B(A3)     
Max % of the face or  20    
Max. diameter  5 mm     
4 Resin pockets, bark pockets 
(if more than one per metre 
total length shall be not 
exceed length given for 
class)  C (C4)   B (E4)   
5 Fissures, shakes      
Max. width  D (D5)    
Max. individual length of 
fissure  F (F5)   F (E5)   DRS 435:2019  
11                ©RSB 2019  - All rights reserved  
 Max. aggregate length  of 
fissures as a percentage of 
the length of each face   E (E5)   F (E5)   
6 Exposed pith  A (A6)     
7 Discoloured sapwood (incl. 
blue stain)b  E (E7)     
8 Ambrosia beetle damage  A (A8)    
9 Sapwood  Not permitted     
10 Growth ring  100 mm     
11 Finger jointing  Not permitted     
12 End jointing  Not permitted     
13 Edge jointing  Not permitted     
14 Laminating  Permitted     
Note * Designation in brackets (e.g.(D1) indicates column and row from Table 1  
  
©RSB 2019  - All rights reserved                  12 
 Bibliography  
[1] Iddi S. and Nagoda  L., Sawmilling and wood preservation in East Africa, 1992  
[2] William F., The Project Gutenberg EBook of Woodwork Joints - How they are set out, how made and 
where used; with four hundred illustrations and index, 2007.  
[3] Les Goring, Manual of Purpose -Made Wood working Joinery, 2014  
[4] ISO 737: 1975, Coniferous sawn timber - Sizes - Methods of measurement  
[5] ISO 8904:1990, Broadleaved sawn timber - Sizes -Methods of measurement  
[6] EN 942:2007, Timber in joinery – General requirements  
[7] EN 350 -2:1994, Durability of wood and  wood -based products  DRS 435: 2019  
 
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