UNIT 5 SUPERSTRUCTURE

Structure
5.1 Introduction
0b;ectives
5.2 Walls
5.3 Brick M ~ S O N ~
5.3.1 Bricks
5.3.2 Mortars
5.3.3 Brick Masonry : Construction Practices
5.3.4 Reinforced Brickwork
5.4 Stone Masonry
5.4.1 Types of Stone Masonry
5.4.2 Stone Masonry :Construction Practices
5.5 Block Masonry
5-6 Partitions
5.7 Summary
5.8 Answers to SAQs

5.1 INTRODUCTION
Superstructure of a building consists of the walls and framing above the foundations. The
structural elements which transmit the loads of the building to the foundation can consist
of load bearing walls or framed construction with infill (non-load bearing) walls.
Struchual framework can be either of steel or reinforced cement concrete (R.C.C.)
construction.
In this unit, we shall deal with walls, materials used for their construction and other
relevant details. Details of R.C.C. and steel constructions are covered in Block I and I1 of
Design Detailing course, respectively.

Objectives
Affer studying this unit, you should be able to
differentiate between various types of walls,
* familiarise yourself with the materials used in such a superstruchue,
* explain various classifications and constructional details of brick, stone and
block masonry, and
describe various types and constructional feahues of partitions.

5.2 WALLS
Let us first try to analyse h e various functions served by walls in a building such as :
(a) support loads of upper floors and roof (in case of load beating walls),
(b) exterior wall of a building has to give protection against nahual elements like
sun, wind, rain, snow etc.
(cj ground floor wall has to resist dampness also,
(d) provides enclosure for ensuring security-andprivacy,
(e) provide support for doors and windows,
(f) provide thermal insulation,
(g) provide sound insulation,
(h) offer adequate resistance to fire, and
(i) serve as a base for suitable aesthetic treatment.
Building Comtmction Walls can be constructed in various ways using a variety of building materials. The
common materials used for construction of walls are as follows :
(a) bricks, (b) stones, and
(c) various types of blocks.
The details of materials and construction practices of walls built from these materials are
described in subsequent sections.

5.3 BRICK MASONRY

Bricks are still one of the most popular materials for construction of walls on account of
its ready availability, ease of handling and construction, and economy.

5.3.1 Bricks
Bricks are made from ordinary clay, moulded and burnt in kilns. They can be hand
moulded or machine pressed or extruded and wire cut. They should be well burnt, of
uniform colour, free from cracks and nodules of free lime. They have, generally, a
depression on one flat face, known as a 'frog'which enables better keying of the mortar
joint. Bricks are available in the traditional nominal dimensions of 22.9 x 11.4 x 7.5 cm
(actual 22.5 cm x 11.1 cm x 7 cm) or modular nominal sizes of 20 cm x 10 cm x 10 cm
(actual 19 cm x 9 cm x 9 cm).
The traditional brick sizes vary in different parts of the country with length from21 to
25 cm, width 10 to 13 cm and height 7 to 7.5 cm. With a view to achieve uniformity of
size throughout the country, the modular size of bricks was standardised by Indian
Standards Institution (now the Bureau of Indian Standards).
Classification of Bricks
Common burnt clay bricks are classified on the basis of compressive strength as
given in Table 5.1.
Table 5.1 :Classification of Bricks

Tolerance on bricks dimension shall be k 3% for designation 10 and above and

f 8% for lower designations. Dimensional accuracy of bricks is necessary for
ensuring proper bond. This is tested by selecting 20 bricks at random and laying
them on a level surface in touch with each other in a straight line and measuring
the total length and calculating the variation with respect to the standard
dimension.
Other important tests to be conducted on bricks are for compressive strength, water
absorption and efflorescence. For bricks of designation 10 and above one test each
shall be done for every 50,000 bricks, while for lower designations the tests can be
carried out for every 1 lakh bricks.
Compressive strength shall be taken as the average strength of five specimens.
However, no value shall be less than 20% of the specified value. The bricks shall
+
be immersed in water for 24 hrs at 27OC 2OC. The surplus water is allowed to
drain off. The frog of the bricks should be filled with 1 : 3 cement mortar flush to
the surface and shall be cured under jute bags for 24 hr. The bricks shall then be
immersed in water for 72 hr. The bricks afer removal shall be wiped clean. Then
the brick shall be placed in the compression testing machine with the flat face
horizontal and mortar filled frog upward. Load shall be applied at a uniform rate of
140 kg/cm2 after placing a plywood sheet on its top . The compressive strength is
the load at failure of the brick, divided by surface area of the brick and is
expressed as kg/cm2. Average of five results shall be taken as the relevant value.
Water absorption shall not exceed 20% by weight upto class 12.5 and 15% by
weight for upper classes. Five bricks shall be tested for water absorption. The
 bricks shall be dried m an oven at 110' to 115'C till they attain a constant weight.
They shall be allowed to cool at room temperature. The cooled bricks shall be
+
weighed. Then they shall be immersed in water at 27OC 2'C for 24 hrs. After
removal they shall be wiped clean and weighed again. The difference between the
two weights as a percentage of the dry weight shall be calculated and the average
of the results for five bricks shall be reported as the value of water absorption.
hflorescence is the crystallisation of water soluble salts in the bricks and results in
white powder on the surface of the bricks, which may result in surface
disintegration of the brick work. It is therefore necessary to test the bricks for
efflorescence. Distilled water is partially filled in a shallow pan and five bricks are
placed on their end so that they are immersed in the water to a depth of 2.5 cm.
The bricks are allowed to absorb the whole water. Distilled water is again poured
into the dish to a depth of 2.5 cm and the water allowed to get absorbed and
evaporate as before. Bricks shall be examined after the second evaporation for
efflorescence. Efflorescene shall be classified as 'nil' if there is no perceptible
deposit of salts, 'slight' when not more than 10% of the area is covered with a thin
deposit of salt, 'moderate' when there is heavier deposit covering upto 50% of the
area, but unaccompanied by powdering or flaking of the surface, 'heavy' when
heavy deposit covers 50% or more of the surface but unaccompanied by powdering
or flaking, and 'serious' when there is heavy deposit of salts accompanied by
powdering and/or flaking of the surface. Bricks having efflorescence beyond
'moderate' shall not be used.
5.3.2 Mortars
There are many types of mortars used in brick work. The type and mix of mortar has to
be decided taking into account the strength required, and, the availability of materials and
skilled labour etc. In general, the strength of the mortar shall not be greater than that of
the masonry unit.
Materials
Water
Water used shall be clean and reasonably free from deleterious materials like oils,
acids, alkalies, salts etc. Potable water is generally considered satisfactory. Water
should be tested for the following characteristics :
(a) Limits of Acidity
To neutralise 200 ml sample of water, it should not require more than 2ml of
0.1 normal caustic soda solution.
(b) Limits of alkalinity
To neutralise 200 ml sample of water, it should not require more than 10 ml of
0.1 normal hydrochloric acid.
(c) Percentage of solids
It shall not exceeed the following limits for various solids :
Organic
Inorganic
Sulphates
Chlorides
Suspended matter 2000 mgfl
(d) The pH value
The pH value of water shall generally be not less than 6.
Cement
Cement shall conform to any one of the following specifications :
(a) 33 grade ordinary portland cement, IS : 269 - 1989
(b) 43 grade ordinary portland cement, IS : 8112 - 1989
(c) 53 grade ordinary portland cement, IS : 1269 - 1987
(d) Rapid hardening portland cement, IS : 8041 - 1990
Bnilding construction (e) Low heat portland cement, IS : 12600 - 1989
(f) Portland Pozzolana cement, IS : 1489 - 1991
(g) Portland slag cement, IS : 455 - 1989
Lime
Lime shall conform to standards given in IS : 712 - 1984.
Building lime shall be classified as follows :
Class A - Eminently hydraulic lime used for structural purposes.
Class B - Semi-hydraulic lime for masonry.
Class C - Fat lime used for finishing purposes; it can be used for masonry
mortar with addition of pozzolanic material.
Class D - Magnesium lime used for finishing coat.
Class E - Kankar lime used for mortar.
Carbide lime obtained as a byproduct in the manufacture of acetyline meets the
requirement of class C lime and can he used for mortar.
Fine Aggregate
This cosists of natural pit or river sand, or crushed stone, most of which passes
,
through IS Sieve 4.75 mm.It shall not contain harmful organic impurities in such
form or quantities (5%)) to affect the strength of the mortar. Sand is generally
classified as fine or coarse.
Fine Sand
This shall be river sand and the grading shall be within the limits of grading
Zone IV of Table 5.2.
Table 5.2 :Grading of Wnc Aggregate

Stone Dust
This shall be obtained by crushing hard stones and the grading shall be within the
limit for Zone I11 of Table 5.2.
Coarse Sand
This shall be either river sand or pit sand and shall conform to the grading of
Zone I11 of Table 5.2
The silt or organic content in fine aggregate should not in any case exceed 8%.The
silt content is tested by placing a sample of sand in a 200 ml measuring cylinder.
The volume of sample will be such that it fills upto the 100 ml mark.Clean water
shall be added upto the 150 rnl. mark. Before adding water dissolve a little salt
(one teaspoon per half litre) in the water. Shake the mixture vigorously. Allow the
contents to settle down for three hours. The height of the silt visible as a layer
above the sand shall be expressed as a percentage of the height of sand below.
Sand having more than the allowable percentage of silt shall be washed to bring
down the silt content within the specified limits.
Cement Mortar
This shall be prepared by mixing cement and sand in the specified proportion for
the given work. For load bearing construction coarse sand is used in the mix of the
mortar. The proportion of cement and sand in cement mortars varies generally
from 1 cement to 3 to 8 of sand, the strength and workability improving wit.
increase in the proportion of cement. Mortars richer than 1 : 3 are not used in
masonry because of high shrinkage with no appreciable gain in the strength of the
masonry. Mortars leaner than 1 : 6 proportion tend to become harsh and, hence,
unworkable.
I
Lime Mortar
This consists of lime as a binder and sand, surkhi, cinder as fine aggregates,
generally in the proportion 1 : 2 or 1 : 3. Lime is slaked and used as lime putty.
Hydrated lime available in powder form can also be used. Lime mortar g m s
strength slowly. The main advantages of lime mortar are its good workability, high
water retentivity and low shrinkage.
Cement Lime Mortar
This type of mortar has some of the advantages of both the types of mortars. It has
medium strength along with good workability and water retentivity. Commonly
adopted proportions are cement : Lime : Sand of 1 : 1 : 6 , l : 2 : 9 and 1 : 3 : 12.
The mix proportion of binder (cement plus lime) to sand is kept as 1 : 3.
The mix proportion and compressive strength of some of the commonly used
mortars are given below :
Table 5.3 :Mix Proportion and Strength of Commonly Used Mortars

Note 1 : A, B, C denote eminently hydraulic lime, semi-hydraulic lime, and

fat lime respectively, as stipulated in IS 7 12 : 1984.
Note 2 : When using plain cement sand mortars (S1. No. 2 (a), 3 (a), 4 (a) and
5 (a)), it ir desirable to include a plasticizer in the mix to improve its
workability.
Note 3 : For Mortu at S1. No. 6, if lime C is used, part of sand should be
replaced by some pomlanic,material, for example, burnt clay or fly
ash, in orda to obtain the requisite strength.
Note 4 : Strength of r mortar may vary appreciably, depending on angularity,
grading and fiieness of sand. Quantity of sand in the mix may, ,
therefore, be varied where found necessary to attain the desired
stregth.
Preparation d Mortar
For proportioning with cement mortar, the unit of measurement is a cement bag of
50 kg whose volume is taken as 0.35 cu m. While measuring sand. allowance shall
Bddiog Corrpt~diOII be given for bulkage (which is the phenomenon of Increase in the v(3lume of sand
with presence of moisture). The amount of bulkage can be determined by making
use of the fact that the volume of inundated sand is the same as that of the dry
sand. To find bulkage, pour the sand upto the 200 ml mark of a 250 rnl measuring
cylinder.Then fill the cylinder with water and stir well. It will be seen that the sand
surface is now below its original level. Suppose the surface i s at Ihe mark - Y ml,
*
the percentage of bulking is f2O:;---- )x 100. The following table glves the
relationship between moisturk content /and percentage of bulking for pracbicle
guidance :

Mixing of mortar shall be preferably done in a mechanical mixer. Cement mortar

shall be used within 30 minutes of mixing. Lime mortar is generally made by
mixing lime putty sand and surkhi and grinding it either manually or in a
mechanical mortar mill. As a rule lime mortar shall be used on the same day it is
made. For lime cement mortar, lime putty and sand shall be ground in a mill and
the required quantity taken out and mixed thoroughly with the specitled quantity of
cement in a mechanical mixer.
In view of easy availability of cement, convenience in use, uniformity of quality
and the difficulty in obtaining lime of good and consistent quality, as well as the
cumbersome process of preparation of lime putty etc., the general practice in the
country is to use cement mortar in masonry.
5.3.3 Brick Masonry : Construction Practices
Bricks are bedded in and jointed with mortar. The bricks are laid to any specific pattern
known as bonds. The primary object of bond IS to give maximum strength to the masonry
and ensure equitable distribution of load. In bonded walls the vertical joints of successive
layers of brickwork are staggered and the pattern gives an attractive appearance to the
wall face. There are many types of bonds but the commonly used ones are Ule English
bond and the Flemish bond which are described here.
English Bond
The bricks in the facing are laid in alternate courses of headers and stretchers. The
header course is commenced with a quoin header followed by a queen closer
(which is a half brick cut longitudinally) and continued with successive headers.
The stretcher courses are formed by stretchers having a minimum lap of one
quarter their length over the header. The Figure 5.1 shows details of the comer of a
one brick wall and a one-and-a half brick wall and also a stopped end.
Flemish Bond
Bricks are laid as alternate header, and stretchers in the same course, the header in
one course being in the centre of the stretcher in the course above and below. In
this bond, in addition to a queen closer, a three-fourth brick bat has to be used. The
Figure 5.2 gives the details with a stopped end.
The choice of the bond depends on the situation, function, load and thickness of
the wall. A Flemish bond gives an attractive appearance while an English bond is
stronger. In our country English bond is used widely for constructing brick
masonry.
Construction
Bricks shall be adequately soaked in water before use. Wetting helps in removing dirt,
dust and ash from the face of the bricks and in spreading of the mortar more evenly under
the brick and also ensures better adhesion. It prevents absorption of water by the bricks
from the mortar which may cause decrease in its strength. The bricks shall he laid In
courses according to the specified bond.
 ..

L
J4 queen elorcq
I 1
topped
end

314 bat
P L A N OF C O U R S E x B P L A N OF C 0 U R S E x . B

I S O M E T R I C V I E W OF O N E - B R I C K W A L L
W l T H C O R N E R AND S T O P P E D E N D

B
A
B
A
B
A

E L E V A T I O N O F WALL W I T H CORNER
P L A N OF CQURSE rA
A N D STOPPED END P L A N OF C O U R S E s A
Oh€ BRICK W A L L ONE AND A H A L F BRICK
WALL -.--

F i g 5.1
~ :Em@& Bond
 314bat
topped Queen
end closer

PLAN Of COURSEx B PLAN OF COURS%xB

I S O M E T R I C VIEW OF O N E 'RICK WALL

-
W l T H C O R N E R AND STOPPED END
r7-n

112 b a t
Quo~nh o l d e r
k e r n closer
Quoln header
ELEVATION WALL W l T H
BEE33
P L A N O F COURSE x A CORNER AND STOPPED 'E NO P L A N OF C O W S E x A _
O N E BRICK WALL ONE A N D A H A L F BRICK
WALL
Bricks shall be laid on a full bed of mortar. Each brick shall be properly bedded by
slightly pressing so that the brick surface is fully in contact with the mortar. All joints
shall be properly flushed and packed with mortar so that no hollow spaces are left.
Properly filled joints ensure strength of the masonry and resistance to penetration of
moisture.
The thickness of joints shall not exceed 1 cm. All the face joints shall be raked to a depth
of 15 mrn during the progress of work when the mortar is still green to ensure proper
keying of plaster or pointing. Where plaster or pointing is not to be done the joints shall
be finished flush at the time of laying.
Scaffolding
In order to construct masonry, scaffolding is used to facilitate the necessary movements
of workers. Double scaffolding having two sets of vertical supports shall be used for all
important works and also where exposed brick work is to be done. In single scaffolding
there is only one set of vertical supports and the wall under construction provides the
other support. In such scaffolding, the placing of the poles on the brick work shall be so
adjusted that they are on the header course, so that only one header is left out for each
pole, which can subsequently be filled up with a full brick. Such holes shall not be
allowed in pillars and columns less than one metre wide.
Curing
The brickwork shall be cured by constantly keeping it wet on all exposed faces for a
minimum period of seven days.
All connected brickwork shall be taken up together and no portion of the work is left
more than one metre below the rest of the work. Where this is not possible the work shall
be raked back, according to the type of bond being followed, in a series of steps at an
angle not steeper than 4j0. Leaving such joints vertical with recesses or toothing in
alternate layers should not be allowed as this will form a plane of weakness.
Cutting and Chasing
As far as possible services such as concealed pipes, conducts etc should be planned with
the help of vertical chases, while horizontal chases should be avoided. For load bearing
walls, the depths of vertical and horizontal chases shall not exceed one-third and
one-sixth the thicbess of the masonry, respectively.
Verticality and Alignment
All masoney shall be built true and plumb within the tolerance limits specified below :
(a) Deviation in verticality in the total height of any wall of a building, more than
+
one storey heigh, shall not exceed 12.5 mm.
+
(b) Deviation from the vertical within a storey shall not exceed 6 mm per 3 m
height.
(c) Deviation from the position shown on the plan of any brickwork, more than one
storey high, shall not exceed 12.5 mrn.
(d) Relative displacement in load bearing walls in adjacent storeys intended to be in
vertical alignment shall not exceed 6 mm.
(e) Deviation of horizontal mortor joints from the level shall not exceed 6 mm upto
12 m length, and for longer length shall not exceed 12.5 mm in total.
a. -Deviation from the specified thickness of horizontal and vertical joints shall not
+
exceed 3 mm,
These tolerances are particularly relevant for load bearing walls.
SAQ 1
(a) What are the different functions served by walls in buildings ?
(b) What are the various tests to be carried out to aqcertain the quality of bricks ?
(c) What is the purposeof providing a bond in the construction of a brickwork ?
5.3.4 Reinforced Brickwork
Plain brickwork is not capable of taking any tensile stress. By providing reinforcement of
steel bars or flats or wire mesh the brickwork would be able to withstand some amount of
tensile force. Such brickwork is known as reinforced brickwork. Good quality bricks of
class designation 7.5 and above and cement mortar not leaner than 1:4 is used in such a
construction. Reinforced brickwork can be used in the construction of retaining walls. In
half brick masonry it is the general practice to provide at every third or fourth course,
reinforcement consisting of two 6 or 8 mm dia bars or hoop iron of dimension
25 mm x 3 mm. Half the mortar for the joint is first laid, the reinforcement placed and the
remaining mortar laid so that the steel is fully embedded in the mortar.

5.4 STONE MASONRY

Stone masonry is a traditional form of construction in this country. However, in view of
the ready availability of bricks and ease of constructing brick-work, the use of stone
masonry is not very common.
Construction of stone masonry requires skilled masons, trained in dressing stones. Large
irregular shaped stones have to be handled as compared to conveniently sized bricks or
blocks. In hilly areas where stones are easily available and for prestigeous buildings
where the architects desire an elevation with stones, this type of masonry is still popular.
The common types of stone available in the country are granite, sandstone, limestone,
basalt, marble etc. The strength of the building stone to be used shall be adequate to carry
the imposed load. The crushing strengths of some of the types of stones are given below :
Type of stone Crushing Strength in ~ / r n r n( ~ ~ l c r n ~ )
Granite 100 (1000)
Sandstone
Limestone
Basalt
Marble
The stones used in the masonry shall be hard, sound, free from cavities, cracks, flaws,
sandholes, veins, patches of soft or loose materials etc. The stone should not contain
deleterious material like iron oxide and organic impurities. All stones should be wetted
before use.
In selecting stones, the situation where this material is to be used has to be considered.
The table below gives the recommended use of common types of stones :
S.No. Situation Type of stone
1. For carved ornamental work, Soft stones like marble,
arches, veneers etc. sandstone
2. For face work of building Granite, Marble and close grained
sandstone
3. Masonry work below plinth Dense stones like granite
level and in subsoil water
4. Masonryworkexposedto Granite, quartzite
smoke or chemical fumes
5. Fire resistant Masonry Compact sandstone
 5.4.1 Types of Stone Masonry
I The common types of stone masonry are listed below :

I (a) Random rubble,

I (b) Squared rubble.
I (c) Coursed rubble, and

I (d) Ashlar.
Random Rubble

I
Stones as obtained directly from the quarry are used, and are only hammer dressed
on tbe face and sides so that they can be bedded properly with the adjacent stones
(Figure 5.3).

Through
stone

Hearting

SECTION X - X

I ,
A g m 5 3 :R d o m Rnhbk UlroPrsbd M.soury

Normally the size of a stone used is such that it can be lifted and placed manually.
The length of the stone shall not exceed three times the height and the breadth on
the base shall not be greater than three-fourth the thickness of the wall and not less
than 15 c m
The wall shall be taken up truly plumb. The stone work may be brought to course
at the plinth, window sill and roof levels. 'Ihe face stones shall extend and bond
well i& the backing. Work should be carried out in such a manner that the joints
are shggered. The face joints shall not be more than 20 mrn thick. Bond or through
stones running right through the thickness of the wall shall be provided at the rate
of one for every 0.5 m2 of the wall area in order to tie the faces and strengthen the
work. If the walls are thicker than 60 cms, instead of providing a single through
stone, two stones one from each face - overlapping by at least 15 cm could be
provided. The quoins or comer stones shall be selected stones, hammer dressed or
chisel dressed and laid as headers and stretchers alternately.
Brought to Course
This is gn improved version of random rubble masonry, except that the work is
roughly levelled up to courses at intervals varying from 300 mrn to 900 mm,
according to the locality and the type of stone used (Figure 5.4).
I
BIliMingComtrodim Squared Rubble
Uncoursed
Ln this type, the stones are roughly squared by hammer, and are laid as risers or
jumpers and stretchers of varying height without bringing to course (Figure 5.5).

SECTION X - X

figure 55 :S q a d Rabble Uaconrsed M ~ s m r y

Brought to Course
Jn this type, the work is levelled upto courses of varying depth from
300 to 900 mm (Figure 5.6).
I
1
SECT ldN X -X

Figure 5.6 :S q d Rubble b o n r y Brought to Course

Coursed Rubble Masonry

Ist Sort
The face stones shall be hammer dressed on all sides to give them approximately
rectangular shape. These shall be squared on all joints and beds (Figure 5.7).
The bed joints are rough chisel dressed to a depth of at least 8 cms from the face
and the side joints for at least 4 cms such that no portion of the dressed surface is
more than 6 mm from a straight edge placed on it. The projections (or bushings) on
the face stone shall not be more than 4 cm beyond the side or bed joint. The
courses shall be laid as alternate headers and stretchers in horizontal layers and the
side joints shall be vertical. The height of each course is nonnally between 15 cm
to 30 cm. No face stone shall be less in breadth than its height and at least one
third of them shall tail into the hearting to a length equal to twice their height. The
hearting or the interior shall also cpnsist of stones carefully laid on their beds.
Chips can be used to fill the interstices but the quantity used should not exceed
10% of the stone masonry. Bond stones shall be provided in every course, the
spacing being 1.5 to 1.8 m. The quoins shall be of the same height as the course
and at least 45 cm long, laid as headers and stretchers. The beds of these stones
shall be chisel dressed to a depth of 10 cm. Generally, quoins have a chisel draft
2.5 cm wide along the edges of the face. The face joints in the masonry shall not be
more than 1 cm thick.
2nd Sort
This is similar to the work discussed earlier, except that the dressing of the joints
could be rougher, with the deviation being 10 rnm from a straight edge and the use
of chips in the hearting could be 15%. Some of the stones in each course could be
of half height so that two stones are used to make up the course. The face joints
could be 2 cm thick.
 FIRST SORT

Bed J

1 hcr joints lo be kcr iolntc to b r

E L f \(ATION hot more than 10 ELEVATION nd rare than 20

Plaster surface Bohd or Rrou h Chi s n6f b escct!d

bushmgnofmre ~shsl50Obb0 15.1 of the auantif~
apart clear c>lld 'of stone nusonry+Hrirting

b i n sb'nc
450 long min.
ODD COURSE
"k 1, r-rted kc& b
I* RIM
ahln C ~ u o i ns t o n
#un% ~ I Plong nin
ODD COURSE

W
.-
masony
,

EVEN COUf?% EVEN COURSE

Agb* 5.7 Coaned Rubble Masonry (All Dimeasions are in mm)

Ashlar
Plain Ashlar
Each stone shall be cut to the required size and shape so as to be free from my
distortion and to give truly vertical and horizontal joints (Figure 5.8). StoP'S are ,#. .

laid in regular courses, not less than 15 cm in height, and upto a maximunl of
30 cm. All the courses shall be of the same height unless otherwise specifiLd.The
length of the stone shall not be less than twice the height and the breadth : base
shall not be greater than three fourth the thickness of the wall nor less tha 15 cm.
The faces that are to remain exposed in the final construction and the adj. dlng
faces shall be fine chisel dressed to a depth of 6 mrn so that when checkt. -4th a
straight edge the variation shall not be more than 1 mrn. The courses sha ~elaid
headers and stretchers alternately unless otherwise specified, and the hm :s shall
be arranged to come as nearly as possible in the middle of stretchcx&ov. md
below. Bond stones shall be provided in every course, 1.5 to 1 8 m apart !re face
joints in the work shall not be more than 5 mm thick.
~ d d i o co-ciioo
g Punched Ashlar
This is similar to plan ashlar except that all exposed faces shall have a fine chisel
draft 2.5 cm wide all round the edges, and shall be rough tooled between the drafts.
such that the dressed surface does not show a variation of more than 3 mm when
checked with a straight edge, This is also laown as rough tooled ashlar
(Figure 5.9).

Figure 5.9 :Punched Ashlar Masonry

Ashlar Rockjiaced
This type is like punched ashlar, with chisel drafting all round the edges of the
exposed face, but the portion within the draft is left rough as it comes from the
quarry except for light hammer dressing to restrict the bushing (projection from the
plane of drafts) to 75 mm (Figure 5.10).
-

Fipre 5.10 :Ashlar Rocldaced Masonry

Ashlar Chamfered
This is similar to plain ashlar except that the edges of the exposed faces are
chamfered to an angle of 45 degrees to a depth of 2 4 mrn as shown in Figure 5.11.
. .

ngwe 5.11 :Ashlar Chamfered M-ry

Ashlar Facing
Here the main wall may be of rubble masonry, brickwork or concrete onto which a
facing of ashlar is provided. In this construction, the appearance is improved by
ashlar face but all the same cost is reduced. ?he back face of. the stone may be left
rough for better adhesion. Bond stones should be provided over the full thickness,
including the backing.
5.4.2 Stone Masonry :Construction Practices
Bureau of Indian Standards has laid detailed rules regarding construction practices.
Bowever, in general, following principles in this regard are in order :
 Mortar for Joints
Same type of mortars are used in stone masonry as in the case of brickwork.
Generally, good quality stone work is built in cement mortar 1 : 3.
Curing
All faces of the masonry work shall be kept moist fur a minimum period of seven
days.
Scaffolding
While single scaffolding can be allowed for rubble masonry, it would be preferable
to have double scaffolding for coursed rubble masonry of first sort.
I In the case of ashlar work only double scaffolding should be permitted.
SAQ 3
L ( a ) Whnt arcb Lhe l:oirm:oi~types of building <tone 11: what qrtdauons arc they

t used ''
(hj WI!ar, is a hc?ndstolle and what i s irs pui!v:sc '!.;':I, wii;i( illlerkals would you
pro-civiilc hond slorjes in rrmdorn rrlhhit., c;?ursectnrhhlr md plain aslldas.
masorif): !'

5.5 BLOCK MASONRY

Various types of blocks can also be used to construct masonry. As these blocks can be
made under controlled conditions it is possible to achieve the desired quality. As they can
b be made to sizes larger than bricks and at the same time true to size and shape, the
construction is faster and the quantity of mortar required for the masonry work is less.
The faces of blocks being fairly smooth, the walls can be left unplastered, and even if
they are plastered the quantity of mortar required would be less than in brick masonry
and very much less than in stone work.
,
A variety of blocks are available for use, such as concrete blocks, lime based blocks, soil
based blocks etc.
Concrete Blocks
Blocks can be solid or hollow. They can be hand made or machine made. The
materials required for their manufacture are cement, aggregate and water. Fly ash
or other admixtures are also, sometimes used. The concrete mix used for the
manufacture of blocks is normally 1 cement to 5 or 6 of combined aggregates (by
volume). The frneness modulus of the combined aggregate shall be between 3.6
and 4. The blocks can be compacted in the moulds manually or preferably
manufactured in block making machines. The blocks shall be cured for 14 days.
Steam curing can be adopted to save time.
The nominal dimensions of concrete blocks are as given below:
Length : 400,500 or 600 mm
Width : 50,75,100,150,200,250 or 300 mm
Height : 100or 200 mm
Hollow concrete blocks are manufactured in three grades, as described below :
Grade A
Load bearing units with a minimum density of 1500k m3. The average
compressive strength shall be 3.5,4.5,5.5 or 7 NfrmnF'(35,45,55 or
70 kg/cm2). The thickness of the face shell and web shall not be less than
25 mm.
Grade B
Load bearing unit with a block density between 1030 lo 1500 kghn). The
average compressive strength shall be 2.3 or 5 Nlmm (20.30 or 50 kg/cm2).
Building Construction Grade C
Non-load bearing units with block density between 1000 to 1%00kgIm3.
average compressive strength shall not L less than 1.5 M / m p (15 kglcm ).
Solid concrete blocks are ma& for load baring units with a block demity of not
less tban 1800 kg/m3. The average compressive strength shall be between 4.0 to
5.O N / d (40 to 50 kg/cm2).
The water absorption of &g mpqete blocks shall not exceed 10% by weight.
Precast Concrete Masonry Blocks
Thwe ace precast solid concrete blocks embedded with stone spalls i.e. broken
stone pieces (2Q w 30% by volume). The concrete is usually made of 1 part of
cement and 9 parts of oombjned f~ and coarse aggregate. The frfixis placed in. the
.
mould in layers along with stone spalls @d compacted.
The blocks are cured for 14 day$. The density mi strength characteristics are
similar to that of solid concrete blocks.
Lime Based Blocks
These are made from a combination of materials consisting of lime, cement, fly
ash, burnt clay pozzolana etc.
The normal nomlnlll ~izesof blocks are
Length : 400 mm
Width : 100,200 or 300 m
Height : 100 or 200 mm
The densip is of the order of 1000 kglm3 and compre8sive strength 3.J N / W ~
(35 kg/cm ),
Llme Flyash Bricks
They are made from fly ash (80-8Q%),sand (2- 12%) and lime (1-10%) with small
quantity of chemical accelerator. They have a density of 1500 kg / m b d a
compressive sgength of 7.5 to 10 N/mm2 (75 to 100 kg/cm2).
Sand Llme Brlcks .
It is composed of sand (91.93%)@pdlit?@(7- 9%). The componenls a? +xed
with water and com ressed in moulds uadsr ptessure an$then autoc1a;ed. m e
density is 800 kg/m8' and compressive s(xepgfi 10 N/mm (100 kg/cm ).
Fly Ash Lime Gypsum Bricks
This is made from a mixture of fly ash, lime, gypsum and sand. After mixing with
water, the mixture is compacted in moulds and cure$ The density is
1400 kg/m3and compressive strength 8 to 10 N/mm (80 to 90 kg/cm2).
Autoclaved Aerated Concrete Blocks
These are made from fine sand or selected quality of fly ash or mixtures of both
and a binder of lime and cement. The cellular character of the blocks, which gives
good thermal properties and a high strength to density ratio, is formed as a result of
aeration caused by adding traces of aluminium powder. These blocks have a
density of 650 k /m3 and compressive strength of 3.5 to 4.0 PJ/mm2
(35 to 40 kglcm4). They have high thermal and sound insulation properties and are
fire resistant also.
Sol1 Based Blocks
Most of the soils can be satisfactorily stabilised by the addition of lime or cement.
It is however necessary to analyse the properties of the soil through a laboratory
testing to determine the optimum quantity of stabilisers to be added to impart the
desired properties to the block. Soil containing 0-10% gravel, 40-75% sand,
15-25% silt, and 8-2596 clay is suitable for making blocks. It showld not contain
more than 0.5% of organic matter and the pH value should be less than 7. Soil
based blocks are cheap and can be used with advantage in the construction of low
cost houses.
These blocks are manufactured from the mixture of suitable soil and a stabilizer
(cement, lime or gypsum or a combination) thoroughly mixed, preferably in a
m o r r h n n i n n l mirnr n t n o..;tnl\lo mn:nh.m n n n t o n t m n r l tho- r.raooarl ; n t n m-mlAo Tka
 blocks are cured for 14 days by gently sprinkling water. Cement (5% by weight) is Superstmcture
generally recommended for non-cohesive soils with low clay content while a
combination of cement and lime (2.5% by weight of each) can be used if the clay
content isJugher. The nominal sizes of the blocks are 20 x 10 x 10 cm 20 x 10 x 5
cm and 30 x 20 x 10 cm The density of the block is about 2000 kg/m3 and the
compressive strength of the order of 2 to 3 ~ 1 r n . m(20
~ to 30 kg/cm2).Water
absorption of the block should be less than 20%.
5.5.1 Blocks Masonry :Construction Practices
The mortar can be cement-sand, lime-sand or combination mortars. The strength of the
t mortar should be weaker than the strength of the blocks to avoid formation of cracks.
Cement sand mortars of 1 :4 to 1 : 6 and corresponding lime or combination mortars
P
t could be used.
C
The blocks may be slightly wetted/moistened before construction to prevent absorption of
water from the mortar and also to ensure proper adhesion with the mortar. The masonry
should be constructed to a suitable bond so that the vertical joints in successive layers are
staggered. The work shall be cured appropriately for due period of time. Scaffolding shall
be single or double depending on the importance of the work.

What are the relative advantages and disadvantages of brick, stone and block
masonry consmctions ?

5.6 PARTITIONS
The space inside a building has to be subdivided into rooms to serve different functions.
This is carried out by partitions which provide enclosures. It ensures privacy, and may
also provide insulation against heat and sound. Openings with door leaves are provided in
these partitions for giving access. The partitions can be permanent or sometimes, as in
offices, it may be desirable to have a system of internal divisions which can be shifted to
suit the possible changes in the use pattern of the spaces. They could be folding or sliding
type also. They normally extend from the floor to the ceiling, but in some offices low
partitions are used to afford a limited degree of privacy. They could be solid, hollow or
louvred. Partitions can be opaque, transparent or translucent. Internal load bearing walls
also serve the purpose of partitions. The details of such walls have already been dealt in
the earlier parts of this unit. Non-load bearing partitions can be constructed from a wide
variety of materials. The choice would depend on a number of factors such as thickness,
weight, sound insulation, cost, ease of construction, necessity to shift, decorative
treatment and fire resistance. For support of non-load bearing partitions, like for half
brick masonry, there should be adequate structural arrangement.
Qpes of Non-load Bearing Partitions
Partitions can be divided broadly into two categories :
(a) Made from blocks and slabs laid in suitable mortar.
(b) Made of boards, sheets etc.
Under the first category fall partitions made from bricks, cement concrete blocks, burnt
clay blocks, gypsum blocks etc. These are normally self-supporting if confined within
permissible spans and heights. The latter category consists of several types of
construction made of wooden panels, plywood, gypsum board, lath and plaster, hard and
soft fibre boards, metal sheets etc. These partitions are framed with timber, metal or
concrete frames, the sheets being fixed to one or both sides by means of screws, nails,
clamps or other means. Alternatively, these partitions can be of built-up construction type
fabricated in factories.
Brick Partitions
These are constructed to half brick thickness by laying the bricks as stretchers. The.
mortar can be of lime or cement. Generally, the mortar used is sand cement mortars
Building Corntruetion of 1 : 3 or 1 : 4 mix. The walls are plastered on both sides. For added strength
reinforcement can be provided as indicated in the Section on reinforced brickwork.
This type of partition is extensively used in buildings and is easy to construct
alongwith the brickwork in the rest of the building. It has a good sound insulation
and f i e resistance properties. The earlier practice of providing timber frames
called nogging and constructing the brickwork within is now not popular.
Block Partitions
This can be built from the various types of blocks described earlier, in suitable
mortar and is generally 10 cm wide. The distance between supports for these
partitions in the vertical or horizontal direction whichever is smaller should not be
more than 48 times the thickness of the blocks. If required, reinforcement as in
reinforced brickwork can be provided and both sides plastered. Hollow burnt clay
blocks can also be used for partitions. They are comparatively lighter being only
about 40 to 50% the weight of a solid brick wall of same thickness and provide
good sound insulation. Other materials like gypsum blocks, wood wool slabs etc
are also used. Glass blocks can be used where light is required to come in. Glass
blocks of various sizes and shapes are available. Generally, they are hollow. It has
to be ensured that no other load than self weight comes on these partitions. The
blocks can be laid in cement lime mortar (1 : 1 : 4). If blocks are larger than 30 cm
the joints are reinforced with hoop iron or expanded metal strips. It has an
attractive appearance, can be easily cleaned and has good Bound insulation
properties.
Partitions of Sheeted Materials
The conventional timber partitions known as stud partitions are constructed of
100 x 75 mm heads and sills with vertical members or studs of 75 x 38 mm or
100 x 50 mm framed at about 400 mm centres (Figure 5.12). The studs are
stiffened by horizontal timber members known as noggings of size 100 x 38 mm.
Timber boards are nailed on both sides of the frame and painted or polished.
Other sheets llke gypsum plaster board, fibre building board, plywood, particle board,
block board, A.C. sheet, G.I. sheet etc., can also be used with a timber frame. The details
of spacing of supports and the spacing of nails for some of the commonly used sheets are
given in Table 5.4.
Table 5.4 :Spacing for Support and Fixlng of Rigid Wall Board

S1. No. Type of Board Thlck- Spacing of Nail Spacing C/C (mm) Min. Edge
ness Supports Clearanceof
(mm) (mm) At W e s At Nails (mm)
(11 (2) (3) (4) (5) (6) (7)
1. Gypsum Board 9.5 400
12.5 500 100 to 150 100 to 150 10
15 600
2. Fire Building 10 400
Board, Particle 12 500 75 150 to 200 10
----- Board etc. 20 600
3. Plywood, Block 6.9 400
Board etc. 12 500 150
16 600
4. Asbestos Board 6 400 150 to 200 150 to 200 -
Note
(1) Nails with shank diameter 2,2.34 or 2.50 mm are commonly used.
(2) Joint thickness shall be of 6 mm.All vertical joints shall be staggered,
particularly when both sides of the wall are covered.
All portions of timber built into or against masonry or concrete shall be given two coats
of boiling coal tar. All wood work shall be painted with approved wood primer.
The framework for fixing the sheets can also be of light steel sections.
Partitions with sheets are light in weight and hence, can be put up directly over slabs.
They are easy to install and can be dismantled without any difficulty.
 Figure 5.12 :TiPllbr Paditiona (All Dimonaiona min mm)

5.7 SUMMARY
In this Unit, we have studied the functions served by walls and partitions. The
characteristics of bricks, tests to be carried out on them to assess their suitability,
different types of mortars used in masonary, importance of bonds and constructional
details of brick masonry have been explained. Similarly, various aspects of stone masonry
have also been given. We have also seen that a masonry can be constructed with blocks,
manufactured from a variety of materials. Lastly, the types of partitions have been
discussed.

5.8 ANSWERS TO SAOs

Refer the relevant preceding text in the unit or other useful books on the topic listed in
the section "Further Reading" at the end of the block to get the answers of the SAQs.