KENYA STANDARD      DKS 2802-8:2019 
ICS  
  
 
 
  
 
  
 
 
 
  
 
  
Masonry units — Methods of test  
 
Part 8:  
Determination of dimensions 
 
Public Review Draft April 2019 
 
 
 
 
  
 
  
 
  
 
  
 
    
 
  
 
  
 
  DKS 2802-8:2019  
ii  © KEBS 2019 — All rights reserved  
 
 
 
© KEBS 2019 First Edition, 2019 
 
 
TECHNICAL COMMITTEE REPRESENTATION 
 
The following organizations were represented on the Technical C ommittee:  
 
National Housing Corporation 
Kenya Clay Products Ltd 
Coast Clay Works Ltd 
Consumer Information Network 
University of Nairobi  
Kenya Industrial Research & Development Institute Architectural Association of Kenya 
M&O Consulting Engineers 
Kenya Association of Manufacturers, 
Kenya National Federation of Jua Kali Association 
Lake Basin Development Authority 
Kenya Bureau of Standards — Secretariat 
 
 
 
  
 
 
 
  
 
 
REVISION OF KENYA STANDARDS 
 
In order to keep abreast of progress in industry, Kenya Standar ds shall be regularly reviewed. Suggestions for 
improvements to published standards, addressed to the Managing Director, Kenya Bureau of Standards, are 
welcome. 
    
© Kenya Bureau of Standards, 2017 
 
Copyright. Users are reminded that by virtue of Section 25 of the Copyright Act, Cap. 130 of 2001 of the Laws of Kenya, copyrig ht subsists 
in all Kenya Standards and except as provided under Section 25 of this Act, no Kenya Standard produced by Kenya Bureau of Stand ards 
may be reproduced, stored in a retrieval system in any form or transmitted by any means without prior permission in writing fro m the 
Managing Director.  
  KENYA STANDARD                                         DKS 2802-8:2019 
ICS  
© KEBS 2019 — All ri ghts reserved   iii  
 
 
 
  
 
Masonry units — Methods of test  
 
Part 8: 
 Determination  of dimensions
 
 
 
 
  
 
  
 
  
 
  
 
  
 
 
KENYA BUREAU OF S TANDARDS (KEBS) 
 
Head Office: P.O. Box 54974, Nairobi-00200, Tel.: (+254 020) 605490, 602350,  Fax: (+254 020) 604031 
E-Mail: info@kebs.org, Web:http://www.kebs.org  
 
Coast Region    Lake Region    Rift Valley Region  
P.O. Box 99376, Mombasa-80100  P.O. Box 2949, Kisumu-40100   P. O. Box 2138, Nakuru-20100 
Tel.: (+254 041) 229563, 230939/40 Tel.: (+254 057) 235 49, 22396  Tel.: (+254 051) 210553, 210555  
Fax: (+254 041) 229448   Fax: (+254 057) 21814 
  DKS 2802-8:2019  
iv  © KEBS 2019 — All rights reserved  
Foreword 
 
This Kenya Standard was prepared by the Clay and Clay Products Technical Committee under the guidance 
of the Standards Projects Committ ee and in accordance with the procedures of the Kenya Bureau of 
Standards. 
 During the development of this standard, reference was made to the following documents: 
 
BS EN 772-16:2011 Methods of test for masonry units - Part 16: Determination of dimensions. 
 
Acknowledgement is hereby made for the assistance received from  these sources. 
  
KENYA STANDARD       DKS 2802-8:2019 
 
 
© KEBS 2019 — All rights reserved   1  
Masonry units — Me thods of test  
 
Part 8:  
Determination of dimensions 
 
1 Scope  
 
This  Kenya Standard specifies a  method of determining  the ov erall dimensions,  thickness and  combined 
thickness  of shells and webs,  depth of voids and plane parall elism of the bed faces of masonry units. 
 
 
2 Normative references 
 The following referenced documents are indispensable for the ap plication of this document.  For dated 
references, only the edition cited applies.   For undated refer ences, the latest edition of the referenced 
document (including any amendments) applies. 
 
DKS 2801-1,   Specification for masonry units-    Part 1:  Clay  masonry units 
 
EN 771-2, Specification for masonry units -   Patt 2: Calcium s ilicate masonry units 
 EN 771-3, Specification for masonry units -    Part 3: Aggregat e concrete masonry units (Dense and light• 
Weight aggregates) 
 
EN 771-4, Specification for masonry units -   Patt 4: Autoclave d aerated concrete masonry units 
 
EN 771-5, Specification for masonry units -   Part 5: Manufactu red stone masonry units 
 EN 771-6, Specification for masonry units -   Part 6: Natural s tone masonry units 
 
3 Principle 
 
After preparation, the length, width and height of the specimen s, the thickness of shells and webs, depth of 
holes and plane parallelism of bed faces are measured with an a ppropriate device. 
 
4 Symbols 
 lu is the length of the masonry unit defined by its intended ori entation in use,  (mm);  
Wu is the width of the masonry unit defined by its intended orie ntation in use, (mm);  
hu is the height of the masonry unit defined by its intended ori entation in use, (mm). 
 
5 Apparatus 
 
An appropriate measuring device or devices  conforming to the requirements for measuring precision given 
in Table 1.     
2  © KEBS 2019 — All rights reserved  
Table 1 — Measurement precision 
 
Tolerance on the dimension being measured   
mm                                         Maximum measuring error 
mm 
< 1 0,1 
1 0.2 
> 1 0,5 
 
If the tolerance class of the dimension being measured is not k nown 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. 
 
6 Preparation of specimens 
 
6.1 Sampling 
 The method of sampling shall be in accordance with the relevant  part of DKS 2801. 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 prod uct specification, in which case that larger 
number shall be used. 
 
6.2 Surface treatment 
 Remove any superfluous material adhering to the unit as a resul t of the manufacturing process before 
measuring. Before measurement of the thickness of webs and shel ls the bed face of the unit should be ground 
to remove any such material. 
 
7 Procedure 
 
7.1 Length, width and height 
 For clay, aggregate concrete, autoclaved aerated concrete, manu factured stone and natural stone masonry 
units determine the  length  (/u), 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 th e positions shown in Figure 1 a). If two 
of the three following conditions are satisfied lu ≤ 250 mm,  Wu ≤ 125 mm, hu ≤ 100 mm, use procedure 
b). 
 
b)  One measurement at the mid point of the unit as shown in  F igure 1 b) using a calliper with overlapping 
jaws aligned along the dotted line. 
 
c) For specimens having irregular surfaces (tongues and grooves , grip holes, rendering keyways, etc.) 
determine the length, width and height at the positions shown i n Figure 1 c). 
 
For calcium silicate masonry units determine the length (/u), t he width ( Wu) and the height ( hu) using procedure   
(d) or procedure ( e) as is relevant. 
 
d) One measurement taken approximately at the centre of each sp ecimen at the positions shown in Figure 1 
(d). 
 
e) For specimens having irregular surfaces (tongues and grooves , grip holes, rendering keyways, etc. 
determine the length, width and height at the positions shown i n Figure 1 e). 
 
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7.2 Thickness of shells and webs 
 
Where  required by the  relevant part of  DKS 2801, measure the  thickness  of the webs  and shells of each 
specimen  for  each  declared  web  and  shell  thickness.  Mea sure at discrete points at three separate 
positions on the type of web or shell being measured. The posit ions 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. 
 
7.3 Depth of holes 
 Where required by the relevant part of DKS 2801, measure the de pth of each hole which does not pass through 
the masonry unit at two different positions. State the result o f each depth measurement to the nearest 0,5 mm. 
 
7.4 Plane parallelism of the bed faces 
 Where required by the relevant part of DKS 2801,   determine th e 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 meas urement to the nearest 0,2 mm. 
 
7.5 Combined thickness of webs and shells 
 
Determine the combined thickness of webs and shells.  This is t he sum of the thicknesses of individual webs 
and shells on a path linking the  formed voids and going from on e face to the opposite face and/or one header 
to the opposite header. Determine the thickness of each individ ual web or shell on the chosen path. 
 NOTE: The path which is chosen ma y not be a straight line, but is the one which gives the lowest combined 
thickness. Some examples are shown in Annex A.  
 
8 Calculation and expression of results 
 
If option  a) or  option c) or option e) of 7 .1   is chosen,  calculate the length Iu),  width ( Wu) and height  ( hu) 
of each  specimen as the mean of the two measurements, where tw o are taken (option e) expressed  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). 
DKS 2802-8:2019  
© KEBS 2019 — All rights reserved   7  
If option b) or option d) or option e) (where one measurement i s taken) of 7.1 is chosen, express the length 
(/u),  width ( Wu) and height ( hu) of each specimen to the nearest 0,1 mm, 0,2 mm or 0,5 mm dep ending on 
the tolerance on the dimension being measured (see Table 1 ).  
Calculate the length, width and height for the sample as the me an of the values of the individual specimens. 
Express the  result to the  nearest 0, 1 mm  when  the  measuri ng  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 sta te this to the nearest 0 ,5 mm. Calculate the 
depth of the holes for the sample as the mean values of the ind ividual specimens to the nearest 1   mm. 
 Calculate the deviation from the plane parallelism as the diffe rence between the maximum and minimum 
measured distance from the corner of the top bed face of the ma sonry unit to the flat surface and express it to 
the nearest 0,2 mm. The deviation from plane parallelism is tak en 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 a nd shells along the imaginary path from one 
face to the opposite face of the unit to the nearest 0,5 mm. Ex press 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.   
9 Test report 
 
The test report shall contain the following information: 
 
a) number, title and date of issue of this  Kenya Standard; 
b) a description of the specimen s to the relevant part of DKS 2 801; 
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; 
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 (/u),  width ( Wu) and height ( hu) of each specimen expressed to the nearest 0, 1 mm, 0,2 mm or  
0,5 mm (see Clause 8), the mean values of length, width and hei ght for the sample being expressed to 
the 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, when required by the relevant part of DKS 2801, stated to the nearest 0,2 
mm for each individual specimen and the value for the sample wh ich is the mean of the individual 
thicknesses stated to the nearest 0,5 mm;  
8  © KEBS 2019 — All rights reserved  
k) mean depth of each hole, where required by the relevant part  of DKS 2801, 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 th e 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 t he mean of the values for the individual units 
expressed to the nearest percent; 
 
o) remarks, if any.  
 
  DKS 2802-8:2019  
© KEBS 2019 — All rights reserved   9 Annex A 
(informative) 
 
 
Examples of paths chosen for the measurement of combined thickn ess 
 
 
 
 
 
  
 
10  © KEBS 2019 — All rights reserved  
 
 
DKS 2802-8:2019  
© KEBS 2019 — All rights reserved   11  
 
 
  
 
  
 
    
 
 
12  © KEBS 2019 — All rights reserved Annex B  
(informative) 
 
 
7 .1   now specifies that for clay, aggregate concrete, autocla ved aerated concrete and natural stone masonry 
units dimensions are to be measured using two measurements for each dimension. In the case of small units 
(which are defined in 7.1),   the measurement may be taken once  for each dimension.  Previously the choice 
of the number of measuring positions had been given in DKS 2801 .   Guidance is given on the measurement 
positions to be used on units with irregular faces and this red uces the number from four previously to two.  This 
can no longer be specified as otherwise in DKS 2801. 
 
Separate provisions are provided for Calcium Silicate units whi ch have irregularities on some of their faces to 
allow single measurements on tho se faces that do not. The guida nce for such units whe re measurements are 
to be taken on faces which have i rregularities is as for other unit types.