ICS91.080.30  
 
Reference number
DRS 536: 2023
© RSB 2023
  
 RWANDA 
STANDARD  DRS 
536 
 
First edition  
2022-mm-dd  
 
Methods of test for masonry 
units — Determination of Dimensions  
   
DRS 536: 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 536: 2023 
iii                ©RSB 2023- All rights reserved 
 Contents Page 
Foreword ............................................................................................................................................................ iv  
1 Scope ...................................................................................................................................................... 1  
2 Normative references ............................................................................................................................ 1  
3 Terms and definitions ........................................................................................................................... 1  
4 Principle ................................................................................................................................................. 1  
5 Symbols (and abbreviated terms) ........................................................................................................ 1  
6 Apparatus ............................................................................................................................................... 1  
7 Preparation of specimens .................................................................................................................... 2  
7.1 Sampling ................................................................................................................................................ 2  
7.2 Surface treatment .................................................................................................................................. 2  
8 Procedure ............................................................................................................................................... 2  
8.1 Length, width and height ...................................................................................................................... 2  
8.2 Thickness of shells and webs .............................................................................................................. 6  
8.3 Depth of holes ........................................................................................................................................ 6  
8.4 Plane parallelism of the bed faces ....................................................................................................... 6  
8.5 Combined thickness of webs and shells ............................................................................................ 6  
9 Calculation and expression of results ................................................................................................ 7  
10 Test report .............................................................................................................................................. 7  
Annex A (normative)  Examples of paths chosen for the measurement of combined thickness.............. 9  
A.1 General ................................................................................................................................................... 9  
 DRS 536: 2023 
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 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. 
RS536was prepared by Technical Committee RSB/TC 9, Civil engineering and building materials.  
In the preparation of this standard, reference was made to the following standard (s): 
BS EN 772-16:2011 Methods of test for masonry units - Part 16: Determination of dimensions 
The assistance derived from the above source is hereby acknowledged with thanks. 
RS536 consists of the following parts, under the general title Methods of test for masonry units — 
Determination of Dimensions 
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 
Greenpack Africa Ltd 
Integrated Polytechnic Regional Centre (IPRC) - Musanze  
Mass Design Group DRS 536: 2023 
v                ©RSB 2023- All rights reserved 
 NP 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 536: 2023 
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  DRS 536: 2023 
1                ©RSB 2023- All rights reserved 
 Methods of test for masonry — Determination of Dimensions 
1 Scope 
This Draft Rwanda standard specifies a method of determining the overall dimensions, thickness and 
combined thickness of shells and webs, depth of voids and plane parallelism of the bed faces of masonry 
units. 
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. 
DRS 546, Clay products for buildings — Vocabulary 
3 Terms and definitions 
For the purposes of this standard, the terms and definitions given in DRS 546  apply. 
4 Principle 
After preparation, the length, width and height of the specimens, the thickness of shells and webs, depth of 
holes and plane parallelism of bed faces are measured with an appropriate device. 
5 Symbols (and abbreviated terms) 
lu              is the length of the masonry unit defined by its intended orientation in use, (mm);  
wu            is the width of the masonry unit defined by its intended orientation in use, (mm);  
hu              is the height of the masonry unit defined by its intended orientation in use, (mm). paragraph. 
6 Apparatus 
An appropriate measuring device or devices conforming to the requirements for measuring precision given in 
Table 1. 
Table 1 — Measurement precision 
Toleranceonthedimensionbeingmeasured 
 
 
mm Maximummeasuringerror 
 
 
mm  
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 <1 0,1 
1 0,2 
>1 0,5 
If the tolerance class of the dimension being measured is not known then the maximum measuring error of the 
measuring device shall be not more than 0.1 mm. 
The device used for measuring the thickness of webs and shells shall have a jaw of at least 10 mm in length. 
7 Preparation of specimens 
7.1 Sampling 
The method of sampling shall be in accordance with the relevant part of EN 771. The minimum number of 
specimens shall be six except in the determination of combined thickness and plane parallelism, where it is 
three, but a larger minimum number may be specified in the product specification, in which case that larger 
number shall be used. 
7.2 Surface treatment 
Remove any superfluous material adhering to the unit as a result of the manufacturing process before 
measuring. Before measurement of the thickness of webs and shells the bed face of the unit should be ground 
to remove any such material. 
8 Procedure 
8.1 Length, width and height 
For clay, aggregate concrete, autoclaved aerated concrete, manufactured stone and natural stone masonry 
units determine the length (lu), the width (wu) and the height (hu) using procedure a), procedure b) or 
procedure c) as is relevant. 
 
 
a) Two measurements taken near the edges of each specimen at the positions shown in Figure 1 a). 
b) If two of the three following conditions are satisfied lu ≤ 250 mm, wu ≤ 125 mm, hu ≤ 100 mm, use 
procedureb).  
c) One measurement at the midpoint of the unit as shown in Figure 1 b) using a calliper with overlapping 
jaws aligned along the dotted line. DRS 536: 2023 
3                ©RSB 2023- All rights reserved d) For specimens having irregular surfaces (tongues and grooves, grip holes, rendering keyways, etc.) 
determine the length, width and height at the positions shown in Figure 1 c). 
e) For calcium silicate masonry units determine the length (lu), the width (wu) and the height (hu) 
usingprocedure(d)orprocedure(e)asis relevant.  
f) One measurement taken approximately at the centre of each specimen at the positions shown in Figure 
1(d). 
g) For specimens having irregular surfaces (tongues and grooves, grip holes, rendering keyways, etc. 
determine the length, width and height at the positions shown in Figure 1 e) 
 
 
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8.2 Thickness of shells and webs 
Measure the thickness of the webs and shells of each specimen for each  declared  web  and  shell  
thickness.  Measure at discrete points at three  separate positions on the type of web or shell being measured. 
The positions should be chosen by visual inspection to be representative of the minimum thickness of the web 
or shell being measured. State the measured thickness of the webs and the shells of each specimen to the 
nearest 0,2 mm. 
8.3 Depth of holes 
Measure the depth of each hole which does not pass through the masonry unit at two different positions. State 
the result of each depth measurement to the nearest 0,5 mm. 
8.4 Plane parallelism of the bed faces 
Determine the plane parallelism of the bed faces of the unit using procedure f) and as shown in Figure 1 f). 
Procedure f): Ensure that the masonry unit is positioned in a stable manner on a flat dimensionally stable 
surface prior to the measurement. Measure the distance from the flat surface to the top of the bed face on all 
four corners of the masonry unit. State the result of each measurement to the nearest 0,2 mm. 
8.5 Combined thickness of webs and shells 
Determine the combined thickness of webs and shells. This is the sum of the thicknesses of individual webs 
and shells on a path linking the formed voids and going from one face to the opposite face and/or one header 
to the opposite header. Determine the thickness of each individual web or shell on the chosen path. 
NOTE         The path which is chosen may not be a straight line, but is the one which gives the lowest combined thickness. 
Some examples are shown in Annex A. 
DRS 536: 2023 
7                ©RSB 2023- All rights reserved 
 9 Calculation and expression of results 
If option a) or option c) or option e) of 7.1 is chosen, calculate the length (lu), width (wu) and height (hu) of 
each specimen as the mean of the two measurements, where two are taken (option e) expressed to the 
nearest 0,1mm, 0,2 mm or 0,5 mm depending on the tolerance on the dimension being measured (see Table 
1). 
If option b) or option d) or option e) (where one measurement is taken) of 7.1 is chosen, express the length 
(lu), width (wu) and height (hu) of each specimen to the nearest 0,1 mm, 0,2 mm or 0,5 mm depending on the 
tolerance on the dimension being measured (see Table 1). 
Calculate the length, width and height for the sample as the mean of the values of the individual specimens. 
Express the result to the nearest 0,1 mm  when  the  measuring error  is  0,1 mm,  0,5 mm when the 
maximum measuring error is 0,2 mm and to the nearest 1 mm when the maximum measuring error is 0,5 mm. 
Calculate the mean web and shell thickness for each specimen to the nearest 0,2 mm. Calculate the thickness 
of webs and shells as the mean of the values of the individual specimens for the sample and express the 
result to the nearest 0,5 mm. 
Calculate the mean depth of each hole, where necessary, and state this to the nearest 0,5 mm. Calculate the 
depth of the holes for the sample as the mean values of the individual specimens to the nearest 1 mm. 
Calculate the deviation from the plane parallelism as the difference between the maximum and minimum 
measured distance from the corner of the top bed face of the masonry unit to the flat surface and express it to 
the nearest 0,2 mm. The deviation from plane parallelism is taken to be the largest value from all of the units 
expressed to the nearest 0,2 mm. 
Calculate the sum of the thicknesses of the longitudinal webs and shells along the imaginary path from one 
face to the opposite face of the unit to the nearest 0,5 mm. Express the result as a percentage of the width of 
the unit to the nearest percent. 
Calculate the sum of the thicknesses of the transverse webs and shells along an imaginary path from one 
header to the opposite header of the unit to the nearest 0,5 mm. Express the result as a percentage of the 
length of the unit to the nearest percent. 
10 Test report 
The test report shall contain the following information: 
a) number, title and date of issue of this Rwanda  Standard; 
b) a description of the specimens  
c) method of sampling and by which organization; 
d) date of receipt of the specimens by the test laboratory; 
e) date of testing the specimens;  
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 f) number of specimens in sample; 
g) a description of the measuring device; 
h) way of measuring [see 7.1 a), b), c), d) or e)]; 
i) length (lu), width (wu) and height (hu) of each specimen expressed to the nearest 0,1 mm, 0,2 mm or0,5 mm (see 
Clause 8), the mean values of length, width and height for the sample being expressed tothe nearest 0,1 mm, 0,5 mm 
or 1 mm (see Clause 8) and the precision of the measuring device; 
j) thickness of shells and webs, , stated to the nearest 0,2 mm for each individual specimen and the value for the 
sample which is the mean of the individual thicknesses stated to the nearest 0,5 mm; 
k) mean depth of each hole, , stated to the nearest 0,5 mm and the mean value for the sample expressed to the 
nearest 1 mm; 
l) maximum deviation from plane parallelism for each unit to the nearest 0,2 mm; 
m) combined thickness of longitudinal webs and shells, which is the mean of the values for the individual units 
expressed to the nearest percent; 
n) combined thickness of transverse webs and shells, which is the mean of the values for the individual units 
expressed to the nearest percent; 
o) remarks, if any. 
 
 
 
 
 
 
 
 
 DRS 536: 2023 
9                ©RSB 2023- All rights reserved Annex A 
(normative)  
 
Examples of paths chosen for the measurement of combined thickness 
A.1 General 
 
 
 
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DRS 536:2023 
 
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