KENYA STANDARD DKS 2801 -1:2018
© KEBS 2017 —All rights reserved iSpecification for Clay Masonry Units
Public Review Draft March2018
© KEBS 201 8 First Edition ,2018TECHNICAL COMMITTEE REPRES ENTATION
The following organizations were represented on the Technical Committee:
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 Manufac turers,
Miritini Building Products Ltd
Kenya National Federation of Jua Kali Association
Kenya Bureau of Standards —Secretariat
REVISION OF KENYA STANDARDS
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for improvements to published standards, addressed to the Managing Director, Kenya Bureau of Standards,
are welcome.
© Kenya Bureau of Standards, 201 7
Copyright. Users are reminded that by virtue of Section 25 of the Copyright Act, Cap. 130 of 2001  of the Laws of Kenya, copyright subsists
in all Kenya Standards and except as provided under Section 25 of this Act, no Kenya Standard produced by Kenya Bureau of Sta ndards
may be reproduced, stored in a retrieval system in any form or t ransmitted by any means without prior permission in writing from the
Managing Director.DKS 2801 -1:2018
Specification for Clay Masonry U nits
KENYA BUREAU OF STANDARDS (KEBS)
Head Office: P.O. Box 54974, Nairobi -00200, Tel.: (+254  020) 60 5490, 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) 23549, 22396 Tel.: (+254 051) 210553, 210555
Fax: (+254  041) 229448 Fax: (+254 057) 21814Foreword
This Kenya Standard was prepared by the Clay and Clay Products Technical Committee under the guidance
of the Standar ds Projects Committee and in accordance with the procedures of the Kenya Bureau of
Standards .
The standard has been developed to replace KS 02 -547:1983 Specification for burnt clay building blocks and
KS 02 -300: 1983 Specification for burnt building brick s. This standard is by all means more comprehensive
and captures the development in the clay industry over the years. This standard may not give specific
dimensions for the clay units but would give values of other parameters to be attained in the testmethods.
In drafting this standard, assistance was sought from the following publications and their use is acknowledged
with appreciation.
BS EN 771 -1:2011+A1:2015 ,EN 771, Specification for masonry units consists of: Part 1: Clay masonry units .
KS 02 -547:1983 Specification for burnt clay building blocks
KS 02 -300: 1983 Specification for burnt building bricksDKS 2801 -1:2018
1.Scope
This Kenya Standard specifies the characteristics and performance requirements for masonry units
manufactured from clay for which the main intended uses are protected or unprotected masonry structure (see
definitions  3.3  and  3.4)  (e.g. Facing and rendered masonry, loadbearing or non -loadbearing masonry
structures, including internal linings and par titions, for bu ilding and civil engineering).
NOTE: Forcontrol purposes, regardless of the use or the compressive strength, that is Protected Units (P) or
Category II Units respectively, the properties of Unprotected Units (U) and Category I Units shall apply.
It defines the performance related to e.g. Dimensional tolerances, strength, density measured according to
the corresponding test method s contained in separate Kenyan Standards.
This Kenyan Standard does not specify standard sizes for clay mason ry units, nor does it specify standard
work dimensions, angles and radii of specia lly shaped clay masonry units. This Kenyan Standard does not
include method of measurement of angles and radii characteristics of speci ally shaped clay masonry units.
ThisKenyan Standard does not cover requirements for the following: units for paving, flue liners and storey
height clay masonry units and clay masonry units with an incorporated thermal insulation material bonded to
thefaces of the unit susceptible to be exposed to fire. It does, however , include clay masonry units for external
chimney masonry.
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 referenced
document ( including any amendments) applies.
DKS 2802 -1 Masonry units —Test Methods —Part 1:  Determination of compressive strength.
DKS 2802 -2 Masonry units —Test Methods —Part 2: Determination of net volume and percent age of voids
of clay masonry units by hydrostatic weighing.
DKS 2802 -3 Masonry units —Test Methods —Part 3: Determination of the active soluble salts content of clay
masonry units.
DKS 2802 -4 Masonry units —Test Methods —Part 4: Determination of wa ter absorption of clay masonry
damp proof course units by boiling in water.
DKS 2802 -5 Masonry units —Test Methods —Part 5: Determination of volume and percentage of voids and
net volume of clay and calcium silicate masonry units by sand filling.
DKS2802 -6 Masonry units —Test Methods —Part 6: Determination of water absorption of aggregate
concrete, autoclaved aerated concrete, manufactured stone and natural stone masonry units due to capillary
action and the initial rate of water absorption of cla y masonry units.
DKS 2802 -7 Masonry units —Test Methods —Part 7: Determination of net and gross dry density of masonry
units (except for natural stone).
DKS 2802 -8 Masonry units —Test Methods —Part 8: Determination of dimensions.
DKS 2802 -9 Maso nry units —Test Methods —Part 9: Determination of moisture expansion of large
horizontally perforated clay masonry units.
DKS 2802 -10 Masonry units —Test Methods —Part 10: Determination of flatness of faces of aggregate
concrete, manufactured stone and natural stone masonry units.
DKS 2802 -11 Masonry units —Test Methods —Part 11: Determination of water absorption of clay and calcium
silicate masonry units by cold water absorption.DKS 2802 -12 Masonry units —Test Methods —Part 12: Determinat ion of initial shear strength.
DKS 2803 Masonry and masonry products —Methods for determining thermal properties.
DKS 2804 -1 Fire classification of construction products and building elements —Part 1:   Classification using
data from reaction to fire tests.
KSISO 12572, hydrothermal performance of building materials and products -Determination of water vapou r
transmission properties.
3.Terms  and definitions
For the purposes of this document , the following terms and definitions apply.
NOTE Annex B tothis Kenyan Standard is informative and gives descriptions of such matters as applications,
exposure and durability.
3.1.
Masonry unit
Preformed component intended for use in masonry construction
3.2.
Clay masonry unit
Masonry unit made from clay or other argillaceous materials with or without sand , fuel or other additives fired
at asufficiently high temperature to achieve a ceramic bond
3.3.
Protected masonry
Masonry which is protected against water penetration and is not in contact with soil and ground water
Note 1   to entry:
It can either be masonry in external walls which is protected, (e.g. by a layer of suitable render or by cladding),
or it can be the inner leaf of a cavity wall or it can be an internal wall. It may or may n ot be loadbearing.
3.4.
Unprotected masonry
Masonry which may be exposed to rain, freeze/thaw and/or may be in contact with soil and ground water
without a suitable protection
Note 1   to entry:
It can either be masonry in external walls which is fully unprotected, or which is intended to be provided by a
limited protection (e.g. by a thin layer of render). It may or may not be loadbearing.
3.5.
P unit
Clay masonry uni t for use in protected masonry.
3.6.
U unit
Clay masonry unit for use in unprotected masonry ~
3.7.
Coordinating size
Size of the coordinating space allocated to a masonry unit including allowances for joints and tolerances
3.8.
Work size
Size of a masonry unit specified for its manufacture, to which the actual size conforms within permissible
deviationsDKS 2801 -1:2018
3.9.
Actual size
Size of a masonry unit as measured
3.10.
Regular -shaped masonry unit
Masonry unit with an overall rectangular parallelepiped sh ape
3.11.
Specially shaped masonry unit
Masonry unit which is not a rectangular parallelepiped
3.12.
Accessory unit
Masonry unit which is shaped to provide a particular function, e.g.  to complete the geometry of the masonry
3.13.
Interlocking features
Shaped matched projections and indentations on masonry units
EXAMPLE Tongue and groove systems.
3.14.
Vertical perforation
Formed void that passes completely through a masonry unit perpendicular to the bed face
3.15.
Horizontal perforation
Formed void that passes completely thr ough a masonry unit parallel to the bed face
3.16.
Cell
Formed void that does not pass through a masonry unit
3.17.
Frog
Depression formed in one or both bed faces of a unit
3.18.
Recess
Depression or indentation in one or more surfaces of a masonry unit
EXAMPLE Mortar pocket, rendering keyway, grip hole.
3.19.
Grip hole
Hole in amasonry unit to enable it to be more readily grasped and lifted by hands or machine
3.20.
Shell
Peripheral material between a perforation and the surface of a masonry unit
3.21.
Web
Solid ma terial between the perforations in a masonry unit
3.22.
Declared value
Value that a manufacturer is confident in achieving, bearing in mind the precision of test and the variability of
the manufacturing process3.23.
Mean compressive strength of masonry units
Arithmetic mean of the compressive strengths of masonry units
3.24.
Normalized compressive strength
Compressive strength of masonry units converted to the air dry compressive strength of an equivalent 100 mm
wide x 100 mm high masonry unit
NOTE          See the p rocedure given inDKS 2802 -1.
3.25.
Damp proof course unit
Clay masonry unit which, when laid in two courses with broken bond in a strong cementitious mortar, will resist
rising damp in masonry
3.26.
High precision clay masonry unit
Clay masonry unit with small dime nsional tolerance especially in unit height
3.27.
Vertically perforated or hollow clay masonry unit
Clay masonry unit with one or more formed voids that pass completely through a masonry unit perpendicular
tothe bed face
3.28.
Horizontally perforated or hollow cl aymasonry unit
Clay masonry unit with one or more formed voids that pass completely through a masonry unit parallel to the
bed face
3.29.
Clay masonry unit for concrete or mortar infill
Clay masonry unit with special perforation suitable for concrete or morta r infill
3.30.
Clay masonry unit for masonry panels
Clay masonry unit suitable for production of reinforced masonry or masonry storey height panels with vertical
channels for mortar or concrete infill
3.31.
Clay masonry subject to severe exposure
Masonry or elemen ts of masonry which, under end use conditions, are subjected to saturation with water
(driving  rain,  ground  water)  combined  with  frequent  freeze/thaw -cycling,  due  to  climatic  conditions  and
absence of protective features
3.32.
Clay masonry subject tomoderate exposure
Masonry or elements of masonry which, under end use conditions, are exposed to moisture and freeze/thaw•
Cycling , excluding constructions subjected to severe exposure
3.33.
Clay masonry subject to passive exposure
Masonry or elements of ma sonry which , under end use conditions, are not intended to be exposed to moisture
and freezing conditions
3.34.
Category I masonry units
Units with a declared compressive strength with a probability of failure to reach it not exceeding 5 %
NOTE         This m ay be determined via the mean or characteristic value.DKS 2801 -1:2018
3.35.
Category II masonry units
Units not intended to comply with the level of confidence of Category I   units
3.36.
Combined thickness of webs and shells
Sum of the thicknesses of the shells and webs from on e face or header of a masonry unit to the opposite face
or header respectively along whichever path, via the formed voids, gives the smallest value , expressed as a
percentage of the unit width or length respectively
3.37.
Product group
Products from one manufa cturer having common values for one or more characteristics
3.38.
Consignment
Shipment from the supplier
3.39.
Product type
Set of representative  performance  levels or classes of a construction  product,  in   relation  to  its essential
characteristics,  manufa ctured using a  given combination of raw materials or other  elements  in a  specific
production process.
4.Materials and manufacture
See 3.2 , 8.3.4 and 8.3.5.
5.Requirements for clay masonry units
5.1. General
The requirements and properties specified in t his standard shall be defined in terms of the test methods and
other procedures referred to in this Kenyan Standard.
NOTE It should be noted that the test methods are not usually applicable to specially shaped and acc essory
units as defined in 3. 11 and 3.12.
In general, for specially shaped clay masonry units it will be satisfactory to declare the properties as that
determined on units of a rectangular parallelepiped shape and of the same product type which has been
subjected to a s imilar manufa cturing process.
The conformity criteria given in the following sub clauses relate to product ty pe determination (see 8.2) and ,
when relevant , toconsignment testing (see Annex A).  For the compre ssive strength of Category I units use a
50 % fractile (p = 0,50) for mean values and a confidence level of 95 %.
For production   evaluation , the manufacturer shall define the conformity criteria in the factory production
control documentation ( see 8.3).
The manufacturer   shall declare whether the unit fulfi lsthe requirements for P units (see Figure 2) or
Uunits ( see Figure 3).
5.2. U units: intended to be used in unprotected masonry
5.2.1. Dimensions and tolerances (U units)
5.2.1.1. Dimensions (U units)The dimensions of a clay masonry unit shall be declared by the manufa cturer in mm for length, width, and
height, in that order (see Figure 1).  They shall be given in terms of work size.
NOTE         In addition the co -ordinating size may be given.
Figure 1 -Dimensions and surfaces
For units of special shape that fit within the envelope of a rectangular parallelepiped shape, the length, width
andheight are those for thetightest envelope .  For other shapes these dimensions are defined in 5.3.2.
NOTE In addition the co -ordinating size may be given.
The m easurement procedure shall be in accor dance with DKS 2802 -8.
5.2.1.2. Dimensional tolerances (U units)
5.2.1.2.1. Tolerances (U units)
The manufacturer shall also declare which of the tolerance categories for mean values in 5.3.1.2.2 the clay
masonry units fulfil.
When rel evant to the uses for which the unit is placed on the market, the manufacturer shall also declare which
ofthe range categories in 5.3.1.2.3 a given consignment of the clay masonry units fulfils.
NOTE          This additional declaration may be made for e xample in relation to:
-achievement of the required accuracy (planarity, bonds and thin layer joints) of the masonry;
-Useof detailed project drawings to achieve these requirements.
5.2.1.2.2. Tolerances of the mean value (U units)
When  clay  masonry  units  are sampled  from  a  consignment  in accordance  with  Annex A  and tested  in
accordance with DKS 2802 -8, the difference for all dimensions between the declared value and the mean
value derived from measurements of the test sample shall be not greater than t he declared one of the following
categories, where the value shall be rounded to the whole mm:
DKS 2801 -1:2018
5.2.1.2.3. Range (U units)
When declared and regular -shaped clay masonry units are sampled from a consignment in accordance with
Annex A and tested in accordance with DKS 2802 -8, the maximum range for any given dimension (i.e. the
difference between the largest and smallest determined dimensions on individual units) to be found within the
test sample shall be within the declared one of the three categories indicated belo w, where the value shall be
rounded to the whole mm:
5.2.1.2.4. Flatness of bed faces (U units)
When  clay  masonry   units  are  intended  to  be used  with  thin  layer  mortar,  the  manufacturer    shall
declare  the maximum  deviation  from  flatness  o f the bed faces.
When  regular -shaped    clay  masonry   units  are  sampled  from  a consignment    in accordance   with
Annex   A and tested   in  accordance    with DKS 2802 -10,   the  deviation   from  flatness   of  the  bed  faces
shall  not  exc eed   the declared  value.
5.2.1.2.5. Plane parallelism of bed faces (U units)
When  clay  masonry   units  are  intended  to  be used  with  thin  layer  mortar,   the  manufacturer    shall
declare  the maximum  deviation  from  plane  parallelism   of the bed f aces.
When  regular -shaped     clay  masonry   units  are  sampled   from  a consignment    in accordance   with
Annex  A and tested   in   accordance    with DKS 2802 -8,   the  deviation   from   plane  parallelism    shall
not  exceed   the  declared value.
5.2.2. Configuration (U units)
Figure 3 -Examples o f Uunits
5.2.3. General (P units)
Figure 2 -Examples of Punits
DKS 2801 -1:2018
When relevant to the uses, for which clay masonry U units are placed on the market , the configuration shall
be decla red.    The  declaration   may  be  made  by  reference   to  one  or  another   of  the  groups   defined
in EN 1996 -1-1     or  EN 1996 -1-2  and/or  it may  include  one  or more  items  such  as those  in the  following
list,   as relevant:
-Shape a ndfeatures,   including  the  direction   of  perforations   (by  means  of a drawing   or
illustration,     when relevant);
-volume  of all formed  voids  as a percentage   of the length  x  width x  height of the unit;
-volume of the largest of any fo rmed voids as a percentage of the length x width x height of the unit;
-volume of grip holes as a percentage of the length x width x  height of the unit;
-thickness of webs;
-thickness of shells;
-combined thickness  of webs and shells from face to face;
-combined thickness of webs and shells from header to header;
-area of voids on a bed face as a percentage of the length x  width of the unit;
-Total volume of frogs as a percentage of the length x width x height of the unit.
NOTE         The header of cla y masonry units may have interlocking features, e.g. Mortar pockets, tongue and
groove systems. The face of clay masonry units may have a surface -profile (rendering keyways).
Forunits of special shape the dimensions to be considered as length, width and height of the unit sha ll be
given.
Each declared value shall be stated as either an upper limit or a lower limit or, alternatively, given as a range
of values.  When clay masonry units are sampled from a consignment in accordance with Annex A and tested
in accordance with DKS 2802 -8,DKS 2802 -5andDKS 2802 -2, the mean value derived from measurements
of the test sample shall be within the range or limit declared.
5.2.4. Density (U units)
5.2.4.1. Gross dry density  (U units)
When relevant to the uses for which the unit isplaced on the market and in all cases for masonry units intended
tobe used in elements subject to acoustic requirements, the gross dry density of clay masonry units shall be
declared by the manufacturer.
NOTE 1               The manufacturer may also pro vide information to show how the declared gross dry density
fits into a national classification system.
When the gross dry density is declared, the manufacturer shall also declare which of the deviation categories
in 5.3. 3.3   applies. This    declaration does not apply to units of special shape.
Forsolid units with or without cells (e.g. frogs or recesses intended to be filled with mortar), the declaration of
the gross dry density and its deviation may be taken equal to the net dry density according to 5.3.3.2.
NOTE 2      This declaration may be made for evaluation of:
-loading;
-airborne sound insulation;
-resistance to fire;-Thermal insulation.
In addition,   the manufacturer may declare the minimum and maximum individual values of gross dry densi ty.
5.2.4.2. Net dry density (U units)
When relevant to the uses for which the unit is placed on the market, the net dry density of clay masonry units
shall be declared by the manufacturer.
NOTE         The manufacturer may also provide information to show how t he declared net dry density fits into
a national classification system.
When the net dry density is declared the manufacturer shall also declare which of the deviation categories in
5.3.3.3 Applies .This declaration does not apply to units of special shap e.
In addition, the manufacturer may declare the minimum and maximum individual values of net dry density.
5.2.4.3. Tolerances (U units)
When  clay  masonry  units are  sampled  from  a  consignment  in accordance  with  Annex A  and  tested  in
accordance with DKS 2802 -7, the mean gross and net dry density derived from  measurements of the test
sample  shall  not differ from the  manufacturer's  declared dry  density  by more than  one of the following
categories:
-D1:       10 %
-D2:       5 %
or
-Dm: a deviati on in % as a whole number declared by the manufacturer (may be wider or closer
than the other categories).
5.2.5. Compressive strength (U units)
When relevant to the uses for which the unit is placed on the market and in all cases for masonry units intended
tobe used in elements subject to structural requirements, the mean compressive strength shall bedeclared
by the manufacturer.  When   relevant , the manufacturer shall also declare the norma lized compressive
strength. In general, for specially shaped c lay masonry units the compressive strength may be declared as
that determined on units of a rectangular parallelepiped shape which have been subjected to a similar
manufacturing process. If the shape of a specially shaped clay masonry unit has a function in resisting load
this shall be taken into account by testing representative samples of whole units but the declaration   of strength
is based upon loading the largest rectangular area normal to the load expected in the brickwork.
NOTE 1 DKS 2802 -1gives in structions on how to convert the unit compressive strength into the normalized
compressive strength.
In addition, the manufacturer shall declare whether the clay masonry unit is Category I.
When the clay masonry units are sampled from a consignment in ac cordance with Annex A and tested in
accordance with DKS 2802 -1, then:
-mean compressive strength of the specified number of clay masonry units from a consignment    shall
be not less than the declared compressive strength;
-Individual strengths of specimens measured within the test sample shall be not less than   80 % of
the declared value.
The declaration shall relate to and indicate the orientation(s ) ofthe clay masonry units as tested, the methods
of bedding the units and whether any voids present are i ntended to be fully filled with mortar.
NOTE 2      The manufacturer may provide information to show how the declared compressive strength fits
into a national classification system.DKS 2801 -1:2018
NOTE 3 fortapered units special provisions apply, seeDKS 2802 -1.
5.2.5.1. Compressive strength values ( Uunits)
When tested in accordance with DKS 2802 -1, the compressive strength for clay units for non -load bearing
blocks shall not be less than 3 N/mm2and the compressive strength for clay units for load bearing b locks shall
not be less than 7 N/mm2.
Table 4 Clay masonry units -Strength classes
DESIGNATION GRADE MIN. COMPRESSIVE
STRENGTH (N/mm2)
Engineering Units U-A 48
Category I Units (Severe Conditions) U-B 28
Category I Units Load Bearing U–C 7
Category I Units Non–Load bearing U-D 3
5.2.6. Thermal properties (U units)
When   relevant to the uses for which the units are placed on the market and in all cases for masonry units
intended to be used in elements subject to thermal insulation requirements, the manufactu rer shall provide the
meanג10,dry,unit -value   and the determination  model as prescribed in DKS 2803 or alternatively give net dry
density  or gross dry density and configuration.
In addition another fractile may be used.  If so the used fractile shall be provided together with t he additional
providedג10,dry,unit -value.
When   the  clay  masonry  units  are  sampled  in accordance  with  Annex A  and tested  in accordance  with
DKS 2803 following the model provided, then the obtained A -value of the specified number of clay maso nry
units shall be not greater than the providedג-value.
When relevant to the use for which the units are placed on the market the value of specific heat capacity given
inDKS 2803 may be provided.
5.2.7. Durabili ty(U units)
The  freeze/thaw  resistance  cate gory  of  a  clay  masonry  unit  shall  be  declared  by the  manufacturer  by
reference to its applicability to masonry or elements subjected to passive, moderate, and severe exposure
(see B.3).
-FO-Passive exposure
-F1-Moderate
-F2-Severe
Until a Kenyan Method of test is available, the freeze/thaw resistance shall be evaluated and declared to the
provisions valid in the intended place of use of the units.
5.2.8. Water absorption (U units)
5.2.8.1. External element (U units)
For clay masonry units intende d to be used in external elements with the face of the unit being exposed the
water absorption ofa consignment shall bedeclared by the manufacturer. When clay masonry units are
sampled from the consignment in accordance with Annex A and tested in accorda nce with DKS 2802 -11, the
mean water absorption of the specified number of clay masonry units shall be not greater than the declared
water absorption.5.2.8.2. Damp proof courses (U units)
The water absorption of clay masonry units intended to be used in damp proof courses shall be declared by
the manufacturer. When clay masonry units are sampled from a consignment in accordance with Annex A and
tested in accordance with DKS 2802 -4, the mean water absorption of the specified number of clay masonry
units shall be not g reater than the declared water absorption.
NOTE         There is no general relationship between water absorption and compressive strength or durability.
5.2.9. Initial   rate of water  absorption (U units )
When relevant for the intended use the range of the i nitial rate of water absorption of a consignment of clay
masonry units shall be declared by the manufacturer. If so and when clay masonry units are sampled from the
consignment in accordance with Annex A and tested in accordance with DKS 2802 -6using an imm ersion
period of (60 ± 2) s the mean initial rate of water absorption of the specified number of clay masonry units shall
fall within the declared range of the initial rate of water absorption.
5.2.10. Active soluble salts content (U units)
When the intended use of the product only provides limited protection (e.g. thin layer of render) or the product
in the intended use is exposed to weather the content of active water soluble salts shall be declared by the
manufacturer on the basis of the categories given in Ta ble 1 .   When clay masonry units are sampled from the
consignment in accordance with Annex A and tested in accordance with DKS 2802 -3,   the content of water
soluble salts shall not be greater than the declared active soluble salts content.
Table 1-Activesoluble salts content categories
NOTE     See B.4 for further information.
5.2.11. Moisture movement (Uunits)
In countries where there is a requirement for moisture movement, it shall be evaluated and declared to the
provisions valid in the intended place of use of the units.
5.2.12. Reaction to fire (U units)
For units intended to be used in elements subject to fire requirements the manufacturer shall declare the
reaction to fire classification of the masonry unit.
For masonry units containing s 1,0 % by mass or volume (whichever is the most onerous) of homogeneously
distributed organic materials the declaration may be fire Class A 1   without the need to test.
Masonry units containing > 1,0 %  by mass or volume (whichever is  the most onerous)  of homogeneous ly
distributed  organic  materials  shall  be classified  in   accordance with DKS 2804 -1and the  appropriate fire
classification declared.
NOTE         Attention  is  drawn  to  the  Commission  Decision  96/603/EC  as  amended by  the  Commission
Decision 2000/605/EC in which non -combustible masonry units containing not more than 1,0  % by mass or
volume (whichever   is the more onerous) of homogeneously distributed organic materials are classifi ed as
reaction to fire Class  A1 without testing.
DKS 2801 -1:2018
5.2.13. Water vapour permeability (U units)
For units intended to be used in external elements, the manufacturer shall provide information on  the  water
vapour  permeability through  the water  vapour  diffusion  coefficient tabulated  values  given   in DKS 2803
ordetermined in accordance with KSISO 12572.
5.2.14. Bond  strength (U units)
5.2.14.1. General (U units)
For clay masonry units intended to be used in elements subjected to structural requirements the bond strength
of the unit in combination with mortar shall be de clared in terms of the characteristic initial shear strength in
accordance withDKS 2802 -12. The declaration may be made either on the basis of fixed values as in 5.2.14.2
or tests as in 5.2.14 .3.     The manufacturer shall declare whether the value of bond strength has been obtained
from the fixed values or from test.
NOTE In most cases it is expected that the use of fixed values will be sufficient.
5.2.14.2. Declaration based  on fixed  values (U units)
When no declaration is made under 5.3.13.3, the chara cteristic initial shear strength of the unit in combination
with mortar may be declared by reference to EN 998 -2:2010, Annex C.
5.2.14.3. Decla ration   based  on tests  (U units)
The characteristic initial shear strength of the unit in combination with one or more specific type of mortar
specified in accordance with EN 998 -2may be declared based on tests on clay masonry units sampled from
a consignment in accordance with Annex A and tested in accordance with Specification for mortar for masonry
2802 -12. The characteristic initial shear strength sha ll not be less than the declared value.
NOTE         Bond strength depends on the mortar, the masonry unit and the workmanship.
5.2.15. Dangerous substances
National   regulations   on  dangerous  substances  may  require verification  and  declaration  on  rel ease,
and sometimes content,  when construction products covered by this standard are placed on those markets.
In the absence of Kenyan harmonized test methods, verification and declaration on release/content should be
done taking into account national provisions in the place of use.
6.Description, designation, designation code and class ification of clay masonry units
6.1. Description and designation
6.1.1. P units
Adescription and designation of a clay masonry unit shall comprise at least the following:
a)Thenumber and date of issue of this Kenyan Standard;
b)Type ofunit (see 5.1) ;
c)Dimensions and tolerances (mean value) (see 5.2.1) ;
d)Gross dry density and tolerances (see 5.2.3).
e)Compressive strength (see 5.2.4);
When relevant to the uses for which the unit is placed on the market, the description and designation shall
include:f)Configuration (see 5.2.2);
g)Tolerances (range) (see 5.2.1);
h)Netdry density and tolerances (see 5.2.3);
i)Thermal properties (see 5. 2.5);
k)Category of active soluble salts 15) content G (see 5.2.8);
l)Moisture movement and its basis (see 5.2.9);
m)Reaction to fire (see 5.2.10 );
n)Water vapour permeability (see 5.2.11   );
o)Bond strength (see 5.2.12);
p)Dangerous substances (see 5.2.13).
6.1.2. U units
A description and designation of a clay masonry unit shall comprise at least the following:
a)Thenumber and date of issue of this Kenyan Standard;
b)Type of unit (see 5.1);
c)Dimensions and toler ances (mean value) (see 5.3.1);
e)Compressive strength (see 5.3.4);
When relevant to the uses for which the unit is placed on the market, the description and designation shall
include:~
f)Configuration (see 5.3.2);
g)Tolerances (range) (s ee 5.3.1);
h)Gross and net dry density and tolerances (see 5.3.3);
i)Water absorption (see 5.3.7);
j)Initial rate of water absorption (see 5.3.8);
k)Thermal properties (see 5.3.5);
I)       ca tegory of active soluble salts content (see 5.3.9);
m)Moisture movement and its basis ( see 5.3.10 );
n)Reaction to fire (see 5.3.11);
o)Water vapour permeability (see 5.3.12);
p)Bond strength (see 5.3.13);
q)Dangerous substances (see 5.3.14).DKS 2801 -1:2018
6.2. Classification
Specificatio n of the properties of clay masonry units may be given by reference to classification systems
provided those systems are based only on single properties included in this standard and do not themselves
constitute a barrier to trade.
This does not remove th e requirement that all manufacturers claiming compliance with this standard shall state
declared values of the properties of their products when required.
7.Marking
The following particulars shall be clearly marked on one of the following: the units, the packaging, delivery note
or any certificate supplied with the clay masonry units:
a)    Name , trademark , or other means of identification of the manufacturer of the unit;
b)    Means of identifying the clay masonry units and relating them to their descri ption and designation.
8.Assessment  and verification of constancy of performance(AVCP)
8.1. General
The  manufacturer  shall demonstrate  compliance  for  his  product with  the  requirements  of this Kenyan
Standard and with the declared 15) performance~ fo r the product properties by carrying out both:
-product type  determination (see  8.2), which  can  be physical testing,  calculation,  reference to
tabulated values or combinations of these methods;
-Factory production control (see 8.3).
Alternative methods of test to the reference methods specified in this Kenyan Standard may be adopted except
for the product type determination tests and in case o' dispute, provided that these alternative methods satisfy
the following:
a)Acorrelation can be show n to exist between the results from the reference method and those from the
alternative method; or
b)Asafe relationship can be demonstrated when using the alternative method compared to the reference
methods and
c)Theinformation on which the relat ionship is based is available.
8.2. Product type  determination
After completion of the development of a new product type and before placing on the market, appropriate
product type determination shall be carried out to confirm that the properties predicted f rom the development
meet the requirements of this standard and the performance of the characteristics to be declared for the
product.
Whenever a major change in the source, blend, or nature of raw materials occurs, or when there is a change
in processing conditions, leading to what the manufacturer considers will constitute a new product type being
produced , the appropriate product type det ermination shall be repeated.
The manufacturer may define product groups. The product group may differ according to thecharacteristics in
question.
In the product type determination process, a manufacturer may take into consideration already existing results.A manufacturer may use the product type determination results determined by someone else (e.g.   another
manufacturer or a research, technology &  development service provider) to justify  his   own declaration of
performance regarding a product that is manufactured according to the same design and with raw materials,
constituents and manufacturing methods of th e same kind, provided that permission is  given by the owner of
the results, and the results are valid for both products.
The tests to be conducted shall be the tests or calculatio ns as described in Table A.2 for the properties selected
from the fo llowing list relevant to the manufacturer's declaration for the product type's intended   use:
-dimensions;
-dimensional tolerances, including flatness and plane parallelism of bed faces;
-configuration;
-dry density and tolerances;
-compressive strength;
-thermal properties;
-freeze/thaw resistance;
-water absorption;
-initial rate of water absorption;
-active soluble  salts content;
-moisture movement;
-reaction to fire;
-Bond strength.
NOTE Sampling for product type determination tests shall be in acc ordance with Annex A. The results of the
product type det ermination shall be recorded.
8.3. Factory production control
8.3.1. General
The manufacturer shall establish, document and maintain a factory production control system to enable
continuing conformity with this Kenyan Standard and the declared performance of the characteristics of the
products placed on the market.
The factory production control system may consist of procedures related to the process only (full process
control and consequently no finished product testing , i.e. 8.3.6 does not apply), to finished products only
(consequentl y no process control, i.e .8.3.5 does not apply ) or any combination  of  both.  Consequently
conformity criteria depend on the individual factory production procedures.
As appropriate, the responsibility, authority and interrelation of all personnel who manage, perform and verify
work affecting the quality of masonry unit products shall be established.
The factory production control system shall describe the control procedure of production, the regular checks
bythe manufacturer and his testing , dependi ngon the combination of the procedures related to process control
and/or finished product testing. Controls and tests may include the characteristics of raw materials and finished
products, the procedure of production, the production equipment or the prod uction machines, the test
equipment or the testing instruments and the marking of the product.
The test results shall be recorded.DKS 2801 -1:2018
Actions to be taken when the control test values or criteria do not meet those specified should be documented
by the manufa cturer.
8.3.2. Testing  and measuri ng equipment
All relevant weighing, measuring and testing equipment, that has an influence on the declared values, shall be
verified and regularly inspected.
8.3.3. Production equipment
When the factory production control system includes process control proced ures, all production equipment,
that forms part of these procedures and has an influence on the declared values shall be regularly inspected.
8.3.4. Raw materials
As appropriate,   the manufacturer shall define the acceptance criteria of raw materials and the p rocedures
operated to ensure that these are met.
8.3.5. Production process
As appropriate, the relevant features of the production processes shall be defined giving the frequency of the
manufacturer’s checks together with the required criteria .Actions to be taken when the criteria are not achieved
shall be specified by the manufacturer.
8.3.6. Finished  product  testing
As appropriate,   the factory production control system shall incorporate a sampling plan and the frequency of
testing of the finished product. The results of sampling and testing shall be recorded.
The sample shall be re presentative of the production.
Depending on the corrective measure, nonconformities may result in higher frequencies of testing than the
ones used.
8.3.7. Statistical techniques
When reasonably practicable and applicable, the results of checks and te sting shall be interpreted by means
of statistical techniques, by attributes or by variables, to verify the product characteristics and to determine if
the production conforms to the compliance criteria and the product conforms to the declared values.
NOT E         One method of satisfying this conformity criterion is to use the approach given in ISO 12491.
8.3.8. Marking and stock control of products
The marking and stock control shall be documented. Individual products or/and a defined quantity of products
(e.g. a consignment of products) should be identifiable and traceable.
8.3.9. Traceability
As appropriate, systems of traceability shall be given in the factory production control system.
8.3.10. Non-conforming products
The     procedure for dealing with nonconforming p roducts shall be documented .  Products that do not conform
totherequirements or the performance of the product type shall be segregated and marked accordingly.
However , these products may be reassessed by the manufacturer and assigned to another produc t type.
The manufacturer shall take action to avoid a reoccurrence of the nonconformity.Annex A
(normative )
Sampling for product type determination tests and for independen t testing of
consignrnents.
A.1   General
This   sampling procedure shall app ly for product type determination tests and in the event that there is a
requirement for an assessment of product compliance.
Only those characteristics declared by the manufacturer shall be assessed by this procedure.
Therequired number of clay masonry units to determine compliance with the specification shall be sampled
from a consignment of masonry units not more than 20 m3(see Table A.1 ).
A.2   Sampling procedure
A.2.1   General
NOTE   The choice of the method of sampling will normally be dictated by the physical form of the consignment
inquestion.
A.2.2 Random sampling
Whenever  possible,  the  random  sampling  method  shall  be  used,  in  which  every  masonry  unit  in  the
consignment    has an equal chance of being selected for the sample. The appropriate number of masonry
units shall   be selected at random from positions throughout the consignment without any consideration being
given to the condition   or quality of those selected except that units damaged in transit shall not be selected.
NOTE         In   practice,  random  sampling  is  normally  only  convenient  either  when  the  masonry  units
forming  the consignment are being moved in a loose (unpacked) form from one place to another or when they
have been split into a large  number of small stacks, e.g. on scaffolding awaiting laying.
A.2.3   Repres entative sampling
A.2.3.1   General
When random sampling is impracticable or not convenient, e.g. when the masonry units form a large stack or
stacks with ready acc ess to only a limited number , a representative sampling procedure shall be used.
A.2.3.2   Sampling from a stack
The consignment shall be divided into at least six real or imaginary sections, each of a similar size. An equal
number of not more than four clay masonry units shall be selected at random from within each section  in order
to give the required number without any consideration being given to the condition or quality of those selected
except that units damaged in  transit shall not be selected.
NOTE 1 Itwill be necessary to remove some sections of the stack or stacks in order to gain access to
masonry units within the body of such stacks when taking samples.
NOTE 2 Sampling from a stack may not be satisfactory when testing for active solu ble sulfates because
contamination from the ground or other sources may occur.
A.2.3.3 Sampling from a consignment formed of banded packs
At least six packs shall be selected at random from a consignment. The band around one blade or slice in
each p ack shall be removed and an equal number of not more than four units shall be sampled at random fromDKS 2801 -1:2018
within each of the broken blades or slices in order to give the required number without any consideration being
given to the condition or quality of those selected except that units damaged in transit shall not be selected.
A.2.4 Dividing the sample
When the sample is to provide clay masonry units for more than one test, the total number shall be collected
together and then divided by taking masonry units at random from within the total sample to form each
successive sub -sample.
The exact number of clay masonry units required for the test(s) as given in Table A.1   and Table A.2 shall be
taken at random from those sampled from the consignment by one of the methods given in A.2.3.
A.2.5     Number of units required for testing
The sample size for each test shall be in accordance withTable A.1 .
Table A.1 –Number of units required for a test
Propert y Clause
NumberTest Method (s)Number of unitsa
Dimensions 5.2.1 DKS 2802:8 10
Flatness of bed faces 5.2.1.2.4 DKS 2802:10 3
Plane parallelism of bed
faces5.2.1.2.5 DKS 2802:8 3
Configuration 5.2.2DKS 2802:8
DKS 2802:2
DKS 2802:510
Gross drydensity 5.2.4.1 DKS 2802:7 10
Net dry density 5.2.4.2 DKS 2802:7 10
Compressive strength 5.1 and 5.2.5 DKS 2802:1 10
Thermal res istance 5.2.6 DKS 2803 -
Water vapour permeability 5.2.13 DKS 2803 or
KS ISO 12572
Freeze / thaw resistance 5.2.7 b c
Waterabsorption 5.2.8 DKS 2802:11(external
elements)
DKS 2802:4 (damp proof
course units )
Initial rate of water absorption 5.2.9 DKS 2802:6
Moisture movement 5.2.11 b c
Active soluble salts content 5.2.10 DKS 2802:3 10
Reaction to fire 5.2.12 DKS 2804:1 -
Bondstrength 5.2.14 DKS 2802:12
Procedure A
Procedure BType I
specimen
27
18Type I I
specimen
18
12
Dangerous substances 5.2.15 National provisi on in place of
use of unit National provisions
aif appropriate e.g when the units are n ot affected by a test procedure, the same test units may be used
for different test.
bTesting according to provisions v alid in the intended place of use of the units.
cThe used provisions give the number to be tested.Annex B
(informative)
Additional informatio n
B.1   Use of clay masonry units
Clay masonry units are used for a large variety of applications, and each requires performance levels to be
specified. Some applications are traditional and the related specification is laid down in standards or traditio nal
rules for good practice. These rules often have a local character, due to climate, building traditions, locally
available materials, maintenance traditions , etc. Other applications might be new and non -traditional, and
formulation   of the performance levels for materials and execution are in that case the responsibility of the
designer.
Particular applications are:
-Common masonry
Masonry used outside or inside having no claim to an attractive appearance.  It may or may not be
load bearing.
-Protect ed masonry
Masonry which is protected against water penetration. It can either be masonry in external walls which
is protected by a suitable layer of render or by a cladding or it can be the inner leaf of a cavity wall or
it can be an internal wall.  It m ay or may not be loadbearing.
-Rendered/ plastered masonry
Masonry used outside or inside which will be rendered/plastered. It may or may not be loadbearing.
-Thermal insulating masonry
Masonry which in itself significantly contributes to the thermal insu lation function of an external wall.
The masonry consists mainly of highly perforated clay masonry units.  It may or may not be
loadbearing.
-Facing  masonry
Masonry used outside or inside that is intended to have an attractive appearance. It is construct ed
from attractive masonry units using a standard of workmanship and mortar joint finish appropriate to
the masonry unit type.  It may or may not be loadbearing.
-Civil  engineering masonry
Masonry used in civil engineering works, e.g .drainage works, ea rthretaining  walls,  etc.,  in which
masonry  units with a high level of durability and compressive strength and a low level of water
absorption are sometimes used.
-Structural  masonry
Masonry used outside or inside that resists loads other than its self-weight. This expression is usually
used in situations where the structural design of the masonry has been carried out by an appropriately
qualified person. Structural masonry may be facing, common , rendered , or civil engineering masonry.
Structural m asonry may also be earthquake resistant.
In connection with the applications cited above, the masonry has such performances as:
-fire resistance;DKS 2801 -1:2018
-sound insulation;
-thermal insulation
Which , if needed, requires additional specifications to be made.
Masonry units should be sufficiently durable to resist local exposure conditions so as to maintain the structural
and operational integrity of the building.
B.2   Durability
Kenyan codes of practice have not yet been prepared dealing with architectural d esign and workmanship,
encompassing the specification and use of masonry units to ensure that satisfactory durability in service in the
finished masonry is achieved. Until these codes become available, it has been found necessary to attach this
annex which relates the grades specified for such properties as freeze/thaw resistance and soluble sulfates
content to service conditions, including the degree of exposure and risk of saturation.
B.3   Freeze/thaw   resistance
B.3.1   General
When making a choice as to which level of freeze/thaw resistance of a masonry unit should be specified for
particular elements of clay masonry, it is necessary to assess the likely degree of exposure to which the units
are to be subjected, including the protection against satu ration of the masonry construction.
The exposure (severe, moderate, and passive) expresses the risk of the masonry being exposed to a high
water content coincident with cycles of freezing and thawing, due to local climatic conditions in combination
with t he design of the construction. The factors forming part of the exposure evaluation are temperature and
moisture conditions as well as the occurrence of any aggressive substances.  In the evaluation it is necessary
to take account of local or national exper iences.
The influence of various surface coatings (plastering, painting) should be evaluated particularly in connection
with thin layer coatings. A surface coating may result in areas with typical temperate coastal climates in
tightened demands for the construction.
Theexamples given in the following are only indicative to help the user to choose the appropriate materials
and are not exhaustive.
B.3.2 Masonry subjected to severe exposure
In the following, examples are given for masonry or masonry ele ments subjected to severe exposure:
-unrendered masonry near to external ground level (approximately two courses above and  below)
where saturation with freezing can occur;
-unrendered parapets where saturation with freezing can occur, e.g.  where the para pet is not provided
with an effective coping;
-unrendered external chimney masonry where saturation with freezing can occur;
-cappings, copings, and sills in areas where freezing conditions can occur;
-freestanding boundary and screen walls where saturatio n with freezing can occur, for example if the
wall is not provided with an effective coping;
-earth retaining walls where saturation with freezing will occur for example where the wall has not been
provided with  an effective coping or a water proofing tre atment on the retaining face.
-B.3.3 Masonry subjected to moderate exposure
In the following, suitable measures to prevent saturation of the masonry are given:
-protection to wall heads by roof overhangs or copings;
-projecting throated sills;
-damp pro ofcourses at the top or base of walls.
B.3.4 Masonry subjected to passive exposure
In the following , examples are given for masonry or masonry elements subjected to passive exposure:
-masonry in external walls if provided with suitable protection, the e xtent of which depends on climatic
conditions: in some parts of Europe, experience suggests that a  thick layer of suitable external render
provides  such a protection; in situations where there  is risk of wetting accompanied  by freezing, the
protection should take the form of an impermeable cladding;
-masonry in internal walls and the inner leaves of cavity walls.
B.4   Sulfate action on mortars and plasters
Sulfate attack on masonry mortars is principally caused by the reaction between sulfate in solu tion and the
tricalcium aluminate  (C 3A) constituent of Portland cement which forms calcium sulfoaluminate (or ettringite).
This reaction only occurs if there is an appreciable C 3A content, found in ordinary Portland cement. The risk is
greatly reduced by the use of sulfate resisting cement, where the C3A content is limited.
Sulfate  attack  occurs  only  if there  is  a  considerable  amount  of water  movement  through  the  masonry.
Diffusion  alone  will  not carry  sufficient  amounts  of  sulfate to the  hydrated cement  in the  mortar. Water
movement may occur by percolation of water through the masonry under the action of gravity, such as in
freestanding  walls,  or below clay  masonry  unit sills where  effective  damp  proof courses  have  not bee n
provided. Movement of water may also be brought about by evaporation and capillary action, for example,
through   retaining walls which are not waterproofed on the retaining face, or in external walls between ground
level and the damp proof course.
Thespecification of the level of soluble sulfates content of clay masonry units with the appropriate grade of
mortar is a complex matter, which may be dealt with in national design codes.
The risk of saturation can be deduced from the exposure categories men tioned in relation to freeze/thaw
resistance in this annex .
The requirement   to declare the active soluble salts content category given  in 5.3.9 is intended to ensure that
under particular   service conditions, damage to the masonry units,  mortar or re nder (if any) will not occur.
The three  categories given in Table 1    specify the maximum content of water soluble sulfates (those of
sodium, potassium  and   magnesium) for use in service conditions where the risks of saturation differ, ranging
from exp ectations  of prolonged saturation  (S2 with  ordinary  Portland cement  in the  mortar or S1   with
sulfate resisting cement  in the masonry mortar or render undercoat), normal exposure to the weather where
the masonry is protected by the design detailin g of the building (S1) to completely dry (SO).  In addition , soluble
Sulfates , especially magnesium sulfate may cause damage to the units themselves , an effect sometimes
known as "cryptoefflorescence", and for this reason, separate requirements for magne sium are given.
For masonry completely protected against water penetration, category SO is assumed to be appropriate. That
means no requirement for the content of active soluble salts is necessary.
8.5   Efflorescence and staining
The appearance of efflorescence in a building is a result of wet masonry drying out and may be due to
excessive wetting during construction, or due to inadequate protection and design detailing, allowing water toDKS 2801 -1:2018
percolate through parts of the completed construction. In additi on, soluble materials from the mortar or from
any adjacent concrete may contribute to the amount of staining and efflorescence observed in practice.
8.6 General Guidance on the appearance of facing clay masonry units
The appearance of masonry units and the assessment should be the subject of purchase contract .  The
requirement will vary according to the use to which the masonry units are to be put, and their inherent
characteristics, e.g. common facing and handmade sho uld be taken into account. As a guide special attention
should be paid to deep or extensive cracks, damage to edges and corners, pebbles and to expansive particles
of lime.