ICS 91.100.15  
 
Reference number  
DRS 514-4: 2022  
© RSB 2022  
  
 RWANDA 
STANDARD  DRS 
514-4  
 
First e dition  
2022 -mm-dd 
 
 
Compressed earth blocks —  
Part 4: Code of practice for production and 
construction  
   
DRS 514-4: 2022  
©RSB 2022  - 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 2022  
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 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 514-4: 2022  
iii                ©RSB 2022  - All rights reserved  
 Contents  Page 
Foreword  ................................ ................................ ................................ ................................ ...................  iv 
1 Scope  ................................ ................................ ................................ ................................ .............  1 
2 Normative references  ................................ ................................ ................................ ...................  1 
3 Terms and definitions  ................................ ................................ ................................ ..................  1 
4 Classification of EMs  ................................ ................................ ...... Error! Bookmark not defined.  
4.1 Classification according to use  ................................ .....................  Error! Bookmark not defined.  
4.1.1  Ordinary EMs (EM O) ................................ ................................ ....... Error! Bookmark not defined.  
4.1.2  Facing EMs (EM F)  ................................ ................................ ...........  Error! Bookmark not defined.  
4.2 Classification according to field of use  ................................ ........  Error! Bookmark not defined.  
4.2.1  Mechanical constraints  ................................ ................................ ... Error! Bookmark not defined.  
4.2.2  Environmental constraints  ................................ .............................  Error! Bookmark not defined.  
5 Designation of EMs  ................................ ................................ .........  Error! Bookmark not defined.  
6 Technical specifications for ordinary earth mortars  ...................  Error! Bookmark not defined.  
6.1 General characteristics  ................................ ................................ ... Error! Bookmark not defined.  
6.2 Textural characteristics  ................................ ................................ .. Error! Bookmark not defined.  
6.3 Appearance characteristics  ................................ ...........................  Error! Book mark not defined.  
6.3.1  General appearance  ................................ ................................ ........  Error! Bookmark not defined.  
6.3.2  Cracks  ................................ ................................ ...............................  Error! Bookmark not defined.  
6.4 Physicochemical characteristics  ................................ ...................  Error! Bookmark not defined.  
6.4.1  Pitting ................................ ................................ ................................  Error! Bookmark not defined.  
6.4.2  Efflorescence  ................................ ................................ ...................  Error! Bookmark not defined.  
6.5 Mechanical, hygrometric and physical characteristics  ...............  Error! Bookmark not defined.  
7 Technical specifications for facing earth mortars  .......................  Error! Bookmark not defined.  
7.1 General c haracteristics  ................................ ................................ ... Error! Bookmark not defined.  
7.2 Textural characteristics  ................................ ................................ .. Error! Bookmark  not defined.  
7.3 Appearance characteristics  ................................ ...........................  Error! Bookmark not defined.  
7.3.1  General appearance  ................................ ................................ ........  Error! Bookmark not defined.  
7.3.2  Cracks  ................................ ................................ ...............................  Error! Bookmark not defined.  
7.3.3  Colour  ................................ ................................ ...............................  Error! Bookmark not defined.  
7.4 Physical -chemical characteristics  ................................ .................  Error! Bookmark not defined.  
7.4.1  Pitting ................................ ................................ ................................  Error! Bookmark not defined.  
7.4.2  Efflorescence  ................................ ................................ ...................  Error! Bookmark not defined.  
7.5 Mechanical, hygrometric and physical characteristics  ...............  Error! Bookmark not defined.  
8 Code of practice for the preparation of earth mortars  ................  Error! Bookmark not  defined.  
8.1 Recommendations on earth selection  ................................ ..........  Error! Bookmark not defined.  
8.1.1  Granular composition  ................................ ................................ ..... Error! Bookmark not defined.  
8.1.2  Plasticity  ................................ ................................ ...........................  Error! Bookmark not defined.  
8.1.3  Nature  ................................ ................................ ...............................  Error! Bookmark not defined.  
8.2 Recommendations for the use of stabilisation addi tives ............  Error! Bookmark not defined.  
8.2.1  Precautions to take when stabilising by adding a physicochemical additive  ................  Error! 
Bookmark not defined.  
8.2.2  Cement stabilisation  ................................ ................................ ....... Error! Bookmark not defined.  
 DRS 514-4: 2022  
©RSB 2022  - All rights reserved                  iv 
 Foreword  
Rwanda Standard s are prepared  by 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 S tandards adop ted 
by Technical committ ees are ratified  by me mbers of RSB Board of Director s for publication and gazettment as 
Rwanda Standards.  
DRS 514-4 was prepared by Technical Committee RSB/TC 9, Civil engineering and building materials.  
In the preparation of this s tandard, reference was made to the following standard:  
ARS 670 -4-2014, Compressed earth blocks - Part 4: Code of practice for production and construction  mortars  
The assistance de rived from the above source is hereby acknowledged with thanks.  
DRS 514 consists of the following parts, under the general title Compressed earth blocks : 
⎯ Part 1: Definitions, classifications, specifications  
⎯ Part 2 Earth mortars  
⎯ Part 3: Test methods  
⎯ Part 4: Code of practice for production and construction  
 
Committee membership  
The following organizations were represented on the Technical Committee on Civil engineering and building 
materials (RSB/TC 9) in the preparation of this standard.  
A+ Construction Group Ltd  
Africeramics Ltd  
Consultants Engineers Group (CEG) Ltd  
D&D Resources Ltd  
Dutureheza Ltd  
Enabel Rwanda  DRS 514-4: 2022  
v                ©RSB 2022  - All rights reserved  
 Greenpack Africa Ltd  
Integrated Polytechnic Regional Centre (IPRC) - Musanze  
Mass Design Group  
NP Construction Construction Company (NPCC) Ltd  
Road Transport Development Agency (RTDA ) 
Rwanda Housing Authority (RHA)  
Rwanda Inspectorate, Competition and Consumer Protection Authority (RICA)  
Rwanda Quarries Association (RQA)  
SKAT Consult  
St Joseph Engineering Company (SJEC) Ltd  
Standards for Sustainability (SfS)  
Stonecraft Industries Ltd  
University of Rwanda - College of Science and Technology (UR - CST)  
Rwanda  Standards Board  (RSB) – Secretariat  
  DRS 514-4: 2022  
1                ©RSB 2022  - All rights reserved  
 Compressed earth blocks — Part 4: Code of practice for production and 
construction  
1 Scope  
This Draft Rwanda Standard describes the processes relating to the production of compressed earth blocks 
(CEBs) and their use in design and construction of housing units. The draft standard is not applicable in areas 
subject to earthquakes, floods or cyclones to an extent that requires the application of appropriate r ules in order 
to avoid major damage.  
2 Normative references  
The following referenced documents are indispensable for the application of this document. For dated 
references, only the edition cited applies. For undated references, the latest edition of the ref erenced document 
(including any amendments) applies.  
DRS 546, Clay products for building – Vocabulary  
3 Terms and definitions  
For the purposes of this standard, the terms and definitions given in DRS 546 apply.  
4 Production of compressed earth blocks (CEBs)  
4.1 Recommendations on earth selection  
Recommendations for earth selection, use of stabilization of additivities, manufacturing parameters, checking 
procedures, delivery of supplies and acceptability of compressed earth blocks (CEB) supplies can be foun d in 
Clause 8.5 of DRS 514 -2. 
 
5  Code of practice for the assembly of compressed earth block masonry  
5.1 Laying out  
 
5.1.1  General  
 
It is on the quality of the layout of buildings that ease of assembly partly depends and as a result the quality of 
the construction, from both a technical and an aesthetic point of view, and this is particularly true for facing 
masonry.  
 
If a detailed br ickwork plan has been prepared, i.e. if the distances (horizontal and vertical) have been defined 
using the dimensions of the blocks used as well as the thickness of the joints, laying out should scrupulously 
respect the dimensions indicated on the plans.  
  
©RSB 2022  - All rights reserved                  2 
 If no detailed brickwork plan has been prepared or if the dimensions of the blocks and/or the thickness of the 
joints differ from what the designer had anticipated, the dimensions given should be modified. Agreement with 
the architect may be needed. Layi ng out should be done according to accepted practice using approved and 
reliable measuring instruments the measurements of which do not vary.  
 
5.1.2  Horizontal laying out  
 
Measuring instruments which enable one to measure directly the greatest lengths of the buildings should be 
used. Flexible tape measures should preferably be metallic. Right angles should be determined by triangulation 
(the 3 -4-5 rule).  
 
The best technique for laying out is to use site boards firmly fixed into the ground; these enable al ignment strings 
to be stretched from nails or saw cuts. The site boards (at least their upper part) must be placed at the same 
level, and this should if possible correspond to the first course of CEBM (or to the upper part of the footing), 
which will enabl e this first course to be perfectly adjusted and therefore to serve as a reference.  
 
5.1.3  Vertical laying out  
 
The upper level of the site boards (horizontally adjusted) should preferably serve as a reference for the masonry 
work. Other points can, however, be used, provided they are firmly fixed.  
 
To respect the vertical distances indicated by the brickwork plan,  gauge rods should be used. These indicate 
the levels of courses and of important elements (window sills, lintels, ring beam, height of wall). Gauge rods can 
be mobile, but should preferably be fixed in strategic points of the building. When the gauge rods  are sufficiently 
rectilinear and rigid, they can serve directly as a support for the strings possibly using strainers, nails or saw 
cuts. These marks are placed at regular intervals corresponding to the vertical brickwork measurements.  
 
5.2 Scaffolding a nd safety  
 
5.2.1  Safety on site  
 
Scaffolding should be erected in such a way as to respect safety regulations. It is standard practice to use safety 
boots and site helmets.  
 
5.2.2  Fixing scaffolding  
 
With facing masonry, fixing scaffolding to the walls sh ould be avoided as this means subsequent patching which 
is not easy. Scaffolding should therefore preferably be positioned sufficiently far away to avoid it banging against 
the wall and may be equipped with a system to prevent this occurring.  
 
With render ed masonry, fixing scaffolding to the walls is not a problem. However, using the wall to support the 
scaffolding should be done only after its capacity to resist specific forces has been checked, and notably with 
regard to the stresses caused by scaffoldin g systems resting on the wall.  
 
5.3 Deliveries and on -site stocks  
 
5.3.1  General  
 
Materials should be checked when they are delivered on site as a minimum by visual inspection. Simple field 
tests can also allow an overall assessment of whether the materia ls delivered conform.  
 
It is recommend ed that the same types of check be carried out just before application, in order to separate out 
materials which might have deteriorated as a result of being badly stocked on site.  
 
5.3.2  Compressed earth blocks  
 DRS 514-4: 2022  
3                ©RSB 2022  - All rights reserved  
 Compressed earth blocks should be unloaded with care. Transporting them on the site should be restricted and 
if possible done with suitable means of transport with a flat loading base.  
 
Blocks intended for facing masonry should be handled with particular care, to avoid chipping them. One should 
therefore seek to restrict unnecessary handling by always stocking them as near as possible to where they are 
to be used. At the same time care should be taken not to overload recently completed scaffolding and floo r 
slabs.  
 
Stocks should be kept in stable piles and on ground which is sufficiently flat and firm and not liable to flooding.  
 
5.3.3  Unstabilised compressed earth blocks  
 
Stocks of unstabilised compressed earth blocks should be protected from rain in ord er to avoid surface erosion. 
If the blocks are stocked directly on the ground, good peripheral drainage should be used, to avoid rising damp 
which could affect the blocks. These measures should be taken only when a risk does exist (e.g. rainy season).  
 
5.3.4 Cement and other binders  
 
These should be stocked sheltered from humidity, or under cover, and raised off the ground on pallets or on 
any other support which allows good ventilation.  
 
5.3.5  Earth and sand intended for preparing laying mortar  
 
Earth an d sand should be stocked on areas which are clean and above all cleared of any vegetation. Earth 
which is to be sieved should be protected from rain as wet earth is impossible to screen.  
 
5.3.6  Earth intended for preparing stabilised earth mortar  
 
In orde r to avoid lumps forming and to ensure the homogeneity of the mix, the earth should not be wet. It should 
therefore be protected from rain and capillary rise.  
 
5.4 Composition, preparation and utilisation of the mortars  
 
5.4.1  General  
 
5.4.1.1  Bonding between compressed earth blocks is generally achieved using mortars prepared from the 
same materials  as the CEBs, in order to achieve compatibility and similar strengths, i.e.:  
 
(a) an earth mortar for unstabilised CEBs;  
 
(b) a stabilised earth mortar for  stabilised CEBs.  
 
The earth used should preferably be of the same nature but can be different in origin.  
 
5.4.1.2  Because no compression occurs, the strength of the mortar obtained is generally lower than that of the 
CEBs. Moreover, the significant water  dosage (approximately 30%) required for the mortar to be easily 
workable, can result in cracking. The generally rapid drying out of mortar, despite the precautions which should 
be taken, can result in the stabilisation being less efficient, and this is pa rticularly the case with low dosages.  
 
For example, in the case of cement, correct practice is to adjust the dosage used for CEBs by:  
 
(a) significantly increasing the proportion of sand to eliminate risks of cracking;  
 
(b) significantly increasing the dosage of stabiliser, i.e. a proportion of approximately 1.5 to 2 times greater 
for low dosages (3 to 6%) and of 1.2 to 1.5 times greater for high dosages (7 to 10%).  
  
©RSB 2022  - All rights reserved                  4 
 5.4.1.3  Cement stabilised compressed earth blocks can also be bonded with sand -based mortars such as the 
following:  
 
(a) sand and quicklime or slaked lime mortar (approx. 1 part lime to 4 parts sand);  
 
(b) sand and hydraulic lime mortar with low dosages (200 to 250 kg/m3); 
 
(c) quarry sand and cement mortar (250 kg/m3). 
 
5.4.1.4  Carrying out preliminary tests, in real conditions on site, allows the most suitable composition to be 
determined.  
 
5.4.1.5  In certain circumstances, it is acceptable to use unstabilised earth mortar for the masonry of stabilised 
earth blocks (e.g .: well protected walls subject to little stress).  
 
5.4.2  Screening the earth  
 
Earth screened using a 10 mm side square mesh is perfectly suitable. Other sizes, however, can also be 
suitable, bearing in mind that the maximum grain size passing through the  mesh can be adjusted by tilting the 
mesh.  
 
It is recommended that the screen should be fairly large in size. Dimensions in the order of 2m × 1m (h × w) are 
perfectly suitable.  
 
5.4.3  Dosages  
 
The materials making up the composition of the mortar should be measured out with precision. Dosage by 
weight is precise, but difficult to carry out on site without special equipment. Procedures for dosing by volume 
are therefore the most commonly used. Using spades to measure out is too imprecise, and not acceptabl e. One 
can, however, use buckets or wheelbarrows when their volume is known. These volumes should correspond to 
a whole number of recipients. Filling regularly, by levelling off and using the entire volume of the recipient are 
essential to obtain a regular  dosage. Using gauge boxes is recommended. These are of predetermined volume 
and therefore enable the prescribed dosage to be matched with a high degree of precision.  
 
Using the sack (of stabiliser) as a basic unit is valid only if the quantity contained is reliable.  
 
5.4.4  Preparing unstabilised earth mortars  
 
These are prepared by mixing water into the earth. The proportion of water is in the order of 30%, but varies 
according to the clay content of the earth. Mixing can be done by hand, in a cement -mixer, or even in a planetary 
or linear mixer.  
 
Preparation c an be done a long time ahead and in large quantities, whether in a dry or a wet state.  
 
As earth absorbs water little by little, mixing is always carried out more liquid than is necessary to achieve the 
workability required for the assembly of compressed earth blocks.  
 
If the earth has started to set through drying out, more water can be added, and as often as necessary, to 
recover the required workability.  
 
5.4.5  Preparing earth mortars stabilised with cement or with hydraulic lime  
 
The earth should be loose. If it is not naturally so, or loose on delivery, it should be screened or broken down, 
even if it contains no grains of too great a size. Loosening the earth is necessary to enable the mixing to take 
place quickly which ensures the homogeneity of th e mix by spreading the stabiliser evenly throughout the mass.  
 
5.4.5.1  Manual mixing  DRS 514-4: 2022  
5                ©RSB 2022  - All rights reserved  
  
The various components are first mixed dry and then the water is added. To obtain good homogeneity, each 
mixing operation should not exceed 5 wheelbarrow loads, i.e.  approximately 300 litres of mix.  
 
Mixing with water should be carried out only for a quantity of mix which can be used within the following half 
hour in order to take advantage of the reaction of the cement with the other components of the mortar. To 
achieve this, mixing with water can be done gradually with small quantities taken from the initial dry mix.  
 
Retempering a mortar which has already taken with water is not permissible as the stabilisation could not occur 
in good conditions and the strength o f the ultimate mortar would be very low (in certain cases even lower than 
that of an unstabilised earth mortar).  
 
5.4.5.2  Mechanical mixing  
 
Mixing can be done using a planetary or linear mixer or even with a simple concrete -mixer.  
 
With a planetary or l inear mixer, mixing takes place as for manual mixing, i.e. first the dry mixing is done, and 
the water is added later. With a concrete -mixer, the filling process is reversed: the water is put in first, then the 
cement is added, followed by the sand (if any ) and finally the earth. For the same reasons as stated for manual 
mixing, the quantities of mortar prepared must be capable of being used within the following half hour and any 
mortar which has already taken should be rejected.  
 
5.4.6  Preparing earth mor tars stabilised with non -hydraulic lime  
 
The mix should be prepared in advance (at least 2 hours before, but preferably one day ahead) and if possible  
covered so that it stays moist until it is used. This gives the lime time to react properly with the clays, without 
hardening through carbonatation occurring, as this takes place only in the presence of air.  
 
5.4.7  Preparing earth mortars stabilised with  bitumen  
 
Bitumen is used in liquid form (cut -back or emulsion). Mixing is carried out with earth which has already been 
mixed with water and is therefore in a liquid state (see preparing unstabilised earth mortars). These mortars can 
be prepared in advanc e. However, remixing them once they have dried out is not advisable.  
 
5.5 Executing the masonry work  
 
5.5.1  Bonding patterns  
 
Compressed earth blocks should be used in masonry in accordance with the detailed brickwork plan already 
drawn up and following a  bonding pattern which respects the rules that there should be no superimposed vertical 
joints and that at least 1/4 of the horizontal surface of the block should be covered. The most common bonding 
patterns are those used for traditional masonry work with  small elements.  
 
5.5.2  Thickness of the mortar  
 
The most common thickness of mortar is 1.5 cm.  
 
To be able to use all the classic bonding patterns, the dimensions of the block should follow the rule:  
 
l = 2 × w + tm (l = length, w = width, tm = thickne ss of the joint).  
 
For fill -in walls with no bonding pattern, it is not necessary to apply this rule.  
 
5.5.3  Wetting the blocks  
 
In order to allow the binder to take, the mortar must be prevented from drying out too quickly. It is therefore vital 
to wet the blocks and the course on which they will rest before laying them. This should be done by sprinkling  
©RSB 2022  - All rights reserved                  6 
 using a whitewash brush or by rapidly dipping them in water. Excessive wetting reduces the quality of the 
masonry work. When using unstabilised CEBs, they should not be wet too much to avoid damaging them. The 
water should be fully absorbed before laying. The water used should not c ontain any deleterious matter.  
 
5.5.4  Cutting blocks   
 
Cutting CEBs as they are being used should be carried out using any tool enabling one to obtain a precise cut 
and a flat surface, e.g. bolsters, saws, disks, etc.  
 
5.5.5  Laying blocks for ordinary ma sonry intended to be rendered  
 
The blocks should be laid on a full bed of mortar in order to ensure that they adhere well. It is recommended 
that the vertical joints should be filled at the same time as laying the CEBs, which is faster but above all more 
efficient than filling in from above after laying.  
 
The joints can be lightly brushed or scratched after laying to allow the render to adhere well.  
 
5.5.6  Laying blocks for facing masonry  
 
The blocks should be laid on a full bed of mortar in order to ensure that they adhere well. It is recommended 
that the vertical joints should be filled at the same time as laying the CEBs, which is faster but above all more 
efficient than filling in from a bove after laying. Using this technique also enables one to obtain a good finish 
more easily. As the mortar oozes out slightly, one has only to scrape off the surplus holding the trowel at an 
angle to obtain a well filled and neat joint that can either be left as it stands or finished off later with a special 
tool.  
 
As a result, the consistency of the mortar is very important. It should not be too liquid as it would drip down the 
wall during laying; nor should it be too dry as this would make it difficult to squeeze the mortar and thus to obtain 
a well filled and neat joint. The mortar should therefore not be laid too far in advance on the preceding course.  
 
5.5.7  Laying the first two block courses  
 
The first two courses will serve as a reference for align ing all the subsequent ones. They therefore have to be 
perfectly aligned (see chapter on laying out). Before proceeding with actually laying these courses, it is 
preferable to try them out dry in order to check that the dimensions and the bonding pattern c orrespond properly.  
 
Adjusting the dimensions is acceptable if this allows simple and correct bonding pattern configurations to be 
used. The thickness of the joints can also be modified without however exceeding ± 5 mm of the thickness 
planned. Laying is then done one block at a time which allows the mortar thickness to be respected and avoids 
running the risk of gradually shifting the bonding pattern along. If the footing is seriously defective in terms of 
flatness, it will take several courses to retriev e horizontality in order to respect the tolerance of ± 5 mm. To 
obtain high strength masonry, it is recommended that the corner blocks should be laid using a plumb line and 
the others using a guide string.  
 
5.5.8  Laying the remaining courses  
 
Each course should be started off in the comers and at the level of wall junctions. Levelling, adjusting to plumb 
and adjusting the height of the course (see chapter on laying out) should be carried out for each of these blocks 
before going on to lay the whole course.   
 
The use of vertical gauge rods is strongly recommended for facing masonry. Vertical gauge rods can be mobile 
or fixed. Laying several levels of blocks in the course before filling in the wall is possible if the mortar sets 
sufficiently quickly and enables the blocks to be adjusted without shifting the blocks on the lower courses and if 
the mortar has negligible shrinkage.  
 
The maximum height of masonry work should not exceed 1m per day.  
 DRS 514-4: 2022  
7                ©RSB 2022  - All rights reserved  
 5.5.9  Jointing for facing masonry  
 
Joints (including dry joints) can  be simply scraped off with a trowel as described above. If necessary, jointing 
can be done using a pointing trowel.  
 
Jointing should preferably be done as soon as the mortar starts to set, i.e. within 1/2 an hour to an hour of laying 
the blocks. The mort ar, which has previously been scraped level with a trowel (after jointing if appropriate) is 
simply pressed in using a tool with a rounded shape (jointer) in such a way as to obtain a finish which is slightly 
hollow, but which does not retain water. More h ollow joint finishes are possible inside or on walls which are well 
protected from bad weather, or with CEBs and EMs which are highly resistant to humidity.  
 
5.5.10  Pointing for facing masonry  
 
The laying mortar is scraped to a depth of at least 2 cm. The  joint is moistened, and as soon as the water has 
been fully absorbed, it is refilled with fresh mortar treated in the same way as described above. This technique, 
which is especially useful for thick masonry, allows a water -resistant mortar to be used on the façade and a 
more weakly dosed mortar for the inside of the wall.  
 
5.5.11  Protecting freshly erected masonry and cleaning  
 
In hot, dry weather and if the walls are built with an earth mortar stabilised with a hydraulic binder, it is advisable 
to prote ct the walls from direct exposure to the sun and to spray them lightly and at regular intervals in order to 
prevent them from drying out too quickly, so that the binder can take correctly.  
 
Walls erected using a non -hydraulic binder (lime) should not be m oistened; on the contrary, for one month after 
laying, they should be protected from the direct effects of bad weather.  
 
Drips or dirty marks should be cleaned off the masonry as soon as it is finished using nonabrasive tools (e.g. a 
sponge or a soft brus h, etc.)  
 
Subsequently, masonry should be protected from blows to avoid any risk of chipping or other damage.  
 
5.6 Bonding with the other construction components  
 
5.6.1  Water proofing from ground humidity  
 
Footings are subject to capillary water rise from surrounding ground which is (even temporarily) wet, when the 
materials used for their construction are permeable. This phenomenon will be accentuated if the evaporation 
capacity of the footing is poor eithe r because it is low or because it has a water proof render.  
 
If this is the case, special technical measures should be used. There are several possible solutions:  
 
(a) very good surface drainage around the building;  
 
(b) the footing is built up sufficiently hig h and has a surface which encourages hydric exchanges, allowing 
water to evaporate before it reaches the CEB wall;  
 
(c) the CEBs used have properties of sufficient wet compressive strength and are capable of resisting 
alternate dry -wet cycles;  
 
(d) a capillary barrier (a layer of sufficiently dosed mortar, bituminous felt, etc.) is interposed between the 
footing and the wall;  
 
(e) a cement slab is interposed between the footing and the wall. In this event, the slab itself should be 
protected from capill ary rise.  
 
5.6.2  Window sills   
©RSB 2022  - All rights reserved                  8 
  
The use of window sills is highly recommended.  
 
Window sills can be integrated into the fixed frame of the wood or metalwork, poured in situ  or prefabricated. In 
the latter case, they should be laid on a bed of mortar.  
 
Except where otherwise prescribed, window sills should jut out from the bare façade by at least 6 cm and should 
be fitted with a throat.  
 
5.6.3  Fixing doors and windows  
 
In the absence of technical specifications proper to the project, fixing doors and wi ndows will be carried out 
according to the following prescriptions.  
 
(1) Placing openings during wall construction   
Wood or metalwork openings (or at least their pre -frame which will be made rigid) should be put into place 
and braced. If the prefabricated  frames are made of wood, they must be perfectly dry so that they do not 
move once they are in position. The bond with the wall is achieved using fixing anchors (for metalwork) 
or 100 mm nails (for woodwork) spaced so that there is a fixing point approxima tely every 5 courses.  
 
The spacing of the fixing anchors should be planned in such a way that they correspond to the location 
of a joint so that they are set into the mortar. Nails should be located between two courses of blocks, 
before the next course is  laid. The mortar used at the level of the fixing points can be stronger than the 
usual mortar if the latter is considered to be too weak.  
 
(2) Placing prefabricated elements after construction   
Special elements should have dimensions corresponding either  to whole blocks, or to half -blocks, so that 
they can be positioned in the walls. These blocks can be made of poured concrete in which a fixing anchor 
has been positioned, or alternatively they can be pre -treated wooden blocks.  
 
(3) Placing openings after  construction by fixing   
There should be at least 4 fixing points for windows and 6 fixing points for doors.  
 
In thick walls, the fixing is achieved by digging a hole shaped like a fish -tail and leaving a gap of at least 
5 cm around the fixing anchor. It is recommended that the bond between the wall and the mortar be 
improved by hammering 100 mm nails in all around the hole. The fixing mortar should preferably be a 
sand -cement mortar dosed to 300 kg/m3 and should be applied with a minimum of water in order  to avoid 
shrinkage.  
 
In thin walls, half -blocks located on either side of the metal or woodwork should be removed. The spaces 
thus liberated should then be dealt with in the same way as described in the previous point. Using a 
formwork is however necessa ry to ensure that the hole is well filled. In the case of metal or woodwork 
which is subject to little stress, as in the case of «Naco» louvre window systems, the same procedure 
can be used by digging only the thickness of the joint and therefore refilling  it after the metal or woodwork 
is in position. This procedure however requires the fixing anchors to be well positioned at the height of 
the joints.  
 
5.6.4  Beams and lintels  
 
Wooden beams and lintels should be placed on a bed of mortar. The same applies to prefabricated concrete 
beams or lintels. Before putting them into position, one should check that these elements are dry and that their 
shrinkage is complete. In the case of concrete beams or lintels poured in situ,  the pouring should be done as 
little liquid as possible in order to avoid to the maximum extent the tensions caused by shrinkage which could 
cause the walls to crack. In the case of buildings with facing masonry, u sing a fairly dry bed of mortar on the 
edges of the formwork is indispensable to fill in inevitable gaps and thus avoid dripping onto the masonry which 
would be very difficult to clean off subsequently.  
 DRS 514-4: 2022  
9                ©RSB 2022  - All rights reserved  
 5.6.5  Ring beams  
 
Using wooden horizontal ring beam s is possible, but the wood should be dry and pre -treated against fungi and 
insects. The bond between the wall and the ring beam is achieved by using 40 mm nails in all the joints. Wooden 
ring beams are placed on a bed of mortar.  
 
Reinforced concrete can be used for ring beams. However, the section of concrete ring beams should be 
minimal so that the forces transmitted during the drying out of the concrete are not too great, thus avoiding the 
danger of cracking in the walls or even destabilising the struct ure.  
 
The concrete used should be sufficiently firm in order to avoid too much shrinkage which could lead to cracking 
in the walls. For buildings with facing masonry, using a fairly dry bed of mortar on the edges of the formwork is 
indispensable to fill in inevi table gaps and thus avoid dripping onto the masonry which would be very difficult to 
clean off subsequently.  
 
Using special compressed earth blocks is particularly recommended as this avoids all of the problems described 
above. Vertical reinforcement shou ld preferably be replaced by simply using thicker masonry.  
 
5.6.6  Tying down the roof  
 
Common roofs should be built according the state of the art relative to building construction.  
 
So-called light roofs should be anchored to the masonry in order to avo id the possibility of being ripped off by 
the wind. In medium risk circumstances, it is recommended that anchoring should be done over a height of 
blocks of at least 40 cm. If possible, the anchoring should be fixed on or under the ring beam.  
 
5.7 Stabili sed renders (earth -sand -cement/lime and sand -cement/lime)  
 
Renders on compressed earth block walls should be applied following the usual rules, proper to each type of 
render. Nevertheless it is advisable to avoid renders which are too thick (maximum 2 cm) and single coat 
covering products in the case of sand -cement/lime renders. It is also appropriate to apply the following 
recommendations.  
 
(1) Preparing the key   
The key should be well prepared by lightly brushing the joints to hollow them out to a depth of no more 
than 2 cm, and by brushing the surface of the blocks if it is too smooth.  
 
(2) Wetting the wall   
 
The wall must be particularly well wet, and several t imes, before applying the render, especially if it is to 
be applied in dry weather.  
 
(3) Sand -cement and sand -hydraulic lime renders   
 
These often fairly rigid renders have a tendency to come away from the walls. To ensure that they stick 
well over time, it is appropriate to:  
 
⎯ carefully check the efficacy of the capillary barrier chosen;  
 
⎯ on stabilised CEB walls, not to use cement dosages which are too high: maximum 250 kg/m3 or 
300 kg/m3;  
 
⎯ on non -stabilised CEB walls, to place a mesh of steel wire (if possible galvanised) stretched 
between nails regularly spaced over a square or triangular screen with 30 cm sides. One wire 
should always be stretched at the level of the edges in the corners of the wall and the window 
ledges.   
©RSB 2022  - All rights reserved                  10 
  
This mesh will be fixed between the two (first) coats of render which should be applied at minimum one day's 
interval and if possible two days' interval.  
 
5.8 Paints, washes and waterproofing products  
 
Applying paints and washes should be carried out acco rding to the known rules proper to each product. 
However, the following rules should be applied:  
 
(1) Preparing the key   
The walls should be dust -free. Any blocks which are too smooth should be brushed beforehand to obtain 
a rough surface providing a good  key.  
 
(2) Wetting   
This is necessary only for cement based washes and should be done thoroughly, and several times.  
 
(3) Thickness   
The thickness of coats of paint and washes should be minimal. Preliminary tests should be carried out to 
determine the id eal mix enabling sufficient coverage with the minimal thickness.  
 
(4) Preparing earth -cement washes   
This type of wash is highly suitable for obtaining a finish which is neat, durable and reliable, at a very low 
cost. The use of white cement and colouring  agents enables one to achieve very high quality finishings.  
 
The earth should be mixed with water until a very liquid wash is obtained. This mix is left to rest for 
approximately 2 minutes so that the largest sand particles settle. The resulting wash is transferred into 
another container and mixed with half its volume in cement, if necessary with an added colouring agent. 
The resulting mix should be vigorously stirred from time to time and used within two hours.  
 
Small colour differences may occur between different preparations. Sufficient quantities must therefore 
be prepared to cover complete wall panels.  
 
(5) Waterproof paints or washes and waterproofing products   
 
Products which form a waterproof coat can be e fficient but are extremely dangerous as they prevent 
water from moving from the inside towards the outside of the wall. If such movement occurs, they can 
blister or fall off, but more seriously, they can cause problems due to stagnant humidity in the walls . As a 
result, such products are usable only if adequate measures are taken to avoid any water infiltration in the 
walls: capillary barriers, protecting the wall at plinth level, good ventilation in the rooms, especially rooms 
with water (bathroom, WC, kit chen, etc.) It is also recommended to use such products only on walls which 
behave well it the presence of moisture.  
 
 
 
5.9 Checking procedures  
 
5.9.1  Laying out  
 
Check that the dimensions given on the plans have been respected.  
 
Check the suitability of the proposed bonding pattern.  
 
If necessary, modify the dimensions indicated on the plans to be able to use simple bonding patterns.  
 
Check that the footing has been levelled.  
 
Beforehand check the gauge rods used by the different builders.  DRS 514-4: 2022  
11                ©RSB 2022  - All rights reserved  
  
5.9.2  Scaffolding  
 
Check that safety standards are being respected.  
 
Check that the scaffolding is not banging against the walls (only for facing masonry).  
 
5.9.3  Deliveries and stocking CE Bs on site  
 
Monitor the care taken when unloading and transporting CEBs using suitable means (flat support bed).  
 
Monitor stocking and identification procedures.  
 
5.9.4  Storage of cement and/or lime  
 
Check that the sacks are carefully stocked sheltered fr om humidity, or covered and raised off the ground on 
pallets or on any other support allowing good ventilation.  
 
There must be visual verification with a fine mesh screen (1 mm) that the cement and/or lime contains no tiny 
lumps which would prove that it had already gone off when accidentally wet.  
 
5.9.5  Storage of earth and sand for the preparation of the mortar  
 
Check that the earth and the sand are stocked on clean areas, are free of organic matter, and are well protected 
(rainy season) from water and humidity.  
 
5.9.6  Screening the earth  
 
Check that the screening operation eliminates any particles larger than those tolerated.  
 
Check that the screen is sufficiently large and is not damaged to avoid projecting larger particles.  
 
5.9.7  Dosage  
 
Check the accuracy of the dosage used after the mortar has dried out (if possible by conducting preliminary 
tests): cracking, resistance to  brushing, resistance to water, or other laboratory tests.  
 
Check the volume of the recipient used.  
 
Verify the procedures for levelling off raw materials when filling measuring recipients.  
 
Verify the daily consumption of materials per m2 actually built. This means knowing the outputs obtained for 
each type of wall or block.  
 
5.9.8  Preparing cement stabilised earth mortars  
 
Verify the homogeneity of the mix. It should contain no foreign bodies. It should contain no lumps (due to poor 
screening).  
 
Check th at the water content is correct (plasticity).  
 
Verify that the wet mix is used within maximum 1/2 hour and , if possible , within less than 1/4 hour.  
 
5.9.9  Laying the blocks  
  
©RSB 2022  - All rights reserved                  12 
 Check the correct practice, wetting the course and the block before laying, using the mortar within the correct 
time limits, laying on a full bed of mortar. Verify that the quality of the mortar (presence and % of large particles) 
enables a good finish to be achieved.  
 
Check the bonding pattern and the thickness of the joints; check that heights are being respected (use of gauge 
rods); check that the verticality and the horizontality of the courses and their rectitude (or curvature) are being 
respected, ta king account of tolerances.  
 
Check any cracking of the mortar.  
 
Check that work is being carried out cleanly.  
 
In dry periods, check that the walls are being regularly moistened for a week after construction.  
 
5.9.10  Window sills and parapets  
 
Check that they are correctly positioned and enable water run -off to occur correctly.  
 
5.9.11  Ring beam and lintels  
 
Verify the bed surface and the laying on a bed of mortar.  
 
With regard to reinforced concrete, if pouring is done in situ,  before this occurs check that the formwork is 
correctly positioned or that some measure has been taken to avoid the concrete running down  the wall.  
 
Verify the plasticity of the concrete (if it is too liquid, its shrinkage could pull on the masonry and cause cracking).  
 
5.9.12  Typing down roofs  
 
Verify the tension of the fixing points and that a very strong protection between the roof stru cture and the top of 
the wall has been used.  
 
5.9.13  Fixing doors and windows  
 
Check that the specifications have been followed.  
 
Check that the number of fixing points conforms to the instructions and that it is sufficient.  
 
5.9.14  Renders  
 
Check that the key has been properly prepared: by brushing, wetting, and if necessary correct fixing of a mesh.  
 
Check that execution has followed the prescriptions and that drying conditions are good.  
 
5.9.15  Finishing  
 
Check the final cleaning of the walls (g entle brushing, dusting off).  
 
5.9.16  Washes  
 
Check walls have been wet beforehand.  
 
Check dosage and correct execution (thickness, homogeneity of colour).  
 DRS 514-4: 2022  
13                ©RSB 2022  - All rights reserved  
 Bibliography  
[1] Compressed earth blocks. Vol. I. Manual of production. CRATerre -EAG: Rigassi V., Aus der Arbeit von 
GATE. Friedrich Vieweg & Sohn, Braunschweig/Wiesbaden, Germany, 1995;  
[2] Compressed earth blocks. Vol. II. Manual of design and construction. CRATerre -EAG: Gui llaud H., 
Joffroy T., Odul P. Aus der Arbeit von GATE, Friedrich Vieweg & Sohn, Braunschweig/Wiesbaden, 
Germany, 1995.  
 DRS 514-4: 2022  
 
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