What are Specifications?

Specifications describe the nature and the class of the work, materials to
be used in the work, workmanship etc. and is very important for the
execution of the work. The cost of a work depends much on the
specifications. Specifications should be clear.

Types of Specifications

Purpose of giving Specifications

 The cost of an unit quantity of work is governed by its specifications.
 Specification of a work is required to describe the quality and quantity
of different materials required for a construction work and is one of the
essential contract documents.
 This also specifies the workmanship and the method of doing the work.
Thus specification of a work serves as a guide to a supervising staff of
a contractor as well as to the owner to execute the work to their
satisfaction.
 A work is carried out according to its specification and the contractor is
paid for the same. Any change in specification changes the tendered
rate.
 As the rate of work is based on the specification, a contractor can
calculate the rates of various items of works in tender with his
procurement rates of materials and labour. Thus tender rate without
specification of works is baseless, incomplete and invalid.
  Specification is necessary to specify the equipment tools and plants to
be engaged for a work and thus enables to procure them beforehand.
 The necessity of specification is to verify and check the strength of
materials for a work involved in a project.
Types of Specifications
1. General Specifications
2. Detailed Specifications
General Specifications
In general specifications, nature and class of works and names of materials
that should be used are described. Only a brief description of each and
every item is given. It is useful for estimating the project. The general
specifications do not form a part of contract document.

Detailed Specifications
The detailed specifications form a part of a contract document. They
specify the qualities, quantities and proportions of materials and the
method of preparation and execution for a particular item of works in a
project. The detailed specifications of the different items of the work are
prepared separately and they describe what the work should be and how
they shall be executed. While writing the detailed specifications, the same
order sequence as the work is to be carried out is to be maintained.
 RCC Specifications

RCC specifications

 Shuttering shall be done using seasoned wooden boards of thickness

not less than 30mm.
 Surface contact with concrete shall be free from adhering grout, nails,
splits and other defects.
 All the joints are perfectly closed and lined up.
 The shuttering and framing is sufficiently braced.
 Nowadays timber shuttering is replaced by steel plates.
 All the props of approved sizes are supported on double wedges and
when taken out, these wedges are eased and not knocked out.
 All the framework is removed after 21 days of curing without any
shocks or vibrations.
 All reinforcement bars conform IS specifications and are free from rust,
grease oil etc.
 The steel grills are perfectly as per detailed specifications.
 The covers to concrete are perfectly maintained as per code.
 Bars of diameter beyond 25mm diameter are bent when red hot.
 The materials proportion should be as per the specifications of the
concrete.
Number of Cement bags required for a specific cement
concrete ratios
 For cement concrete of ratio 1:1:2(1 cement:1sand/coarse
sand:2graded stone aggregate) require 11no bags of 50kg.
 For cement concrete of ratio 1:1.5:3 require 7.8no bags of 50kg.
 For cement concrete of ratio 1:2:4 require 6 no bags of 50kg.
 For cement concrete of ratio 1:3:6 require 4.25no bags of 50kg.
 For cement concrete of ratio 1:4:8 require 3.2 no bags of 50kg.
 For cement concrete of ratio 1:5:10 require 2.50 no bags of 50kg.
 For cement concrete of ratio 1:6:12 require 2.25 no bags of 50kg.

Brick Masonry with Cement Mortar

Masonry is the building of structures from individual units laid in and bound

together by mortar; the term masonry can also refer to the units

themselves. The common materials of masonry construction are brick,

stone such as marble, granite, travertine, limestone, concrete block, glass

block and tile. Masonry is generally a highly durable form of construction.

Brick masonry construction involves use of high quality materials in

construction. Use of low grade materials in construction or mortar mix in

inappropriate ratio can affect the quality of construction.

Specifications for Brick masonry in Cement Mortar
 The bricks shall be of first class, regular in shape, size and colour.
 The bricks should be free from flaws, cracks and lumps of any kind.
 Shall have minimum crushing strength 10.5N/mm2.
 The bricks shall not absorb the water more than one sixth of the weight
of the brick.
 The sand used shall be medium coarse, clean, sharp, free from clay,
mica and other organic matter.
 The cement used shall satisfy the requirement of Bureau of Indian
Standard.
 The mortar is designated in specified proportion of cement and sand.
The materials are weighed or measured and mixed on watertight
platform after allowing bulkage of sand.
 Bricks before laying shall be thoroughly soaked in water.
 The bricks laid truly horizontal in course with frogs upwards.
 The brickwork shall be raised 1m in height at a strength all round the
building.
 Only fresh mortar within ½ hour for cement mortar, the time of adding
water shall be used.
 During rains, no brickwork is carried out when special arrangements
are made.
 The brickwork shall be kept wet for atleast 10 days.
 Specifications for Plain Cement Concrete (PCC)

Plain Cement Concrete (PCC) is a construction material generally used

as a binding materials and is composed of cement, (commonly Portland
Cement) and other cementitious materials such as fly ash and slag cement,
aggregate (generally a coarse aggregate made of gravels or crushed rocks
such as limestone or granite, plus a fine aggregate such as sand), water,
and chemical admixtures.

Cement mixing with sand

Specifications for Plain Cement Concrete (PCC)
Materials Specifications
Aggregate shall be of invert materials and should be clean, dense, hard,
sound, durable, non-absorbent and capable of developing good bond with
mortar.
Coarse aggregate shall be of hard broken stone of granite or similar stone,
free from dust, dirt and other foreign matters. The stone ballast shall be of
20mm size and smaller. All the coarse material should be retained in a
5mm square mesh and should be well graded such that the voids do not
exceed 42%.
Fine aggregate shall be of coarse sand consisting of hard, sharp and
angular grains and shall pass through a screen of 5mm square mesh. Sand
shall be of standard specifications, clean and free from dust, dirt and
organic matter. Sea sand shall not be used.
Cement shall be fresh Portland cement of standard ISI
specifications and shall have the required tensile and compressive
stresses and fineness.
Water shall be clean and free from alkaline and acid matters and suitable
for drinking purposes.
Proportion Specifications
1:2:4 (cement : sand : stone ballast) by volume when specified. Minimum
compressive strength of concrete of 1:2:4 proportion shall be 140 kg/cm2 in
7 days.

Hand mixing
Mixing shall be done on masonry platform or sheet iron tray.
Machine mixing
Stone ballast, sand and cement shall be put into cement concrete mixer to
have the required proportions.

Slump
Regular slump test should be carried out to control the addition of water
and to maintain the required consistency. A slump of 7.5cm to 10cm may
be allowed for building work.

Formwork
Formwork centering and shuttering shall be provided as required as per the
standard specification before laying concrete to confine to support or to
keep the concrete in position. The inner surface of shuttering shall be oiled
to prevent concrete sticking to it.

Laying Technique
Concrete shall be laid gently (not thrown) in layers not exceeding 15cm and
compacted by pinning with rods and tamping with wooden tampers or with
mechanical vibrating machine until a dense concrete is obtained.

Curing Method
After about two hours of laying of concrete, when the concrete has begun
to harden, it shall be kept damp by covering with wet gunny bags or wet
sand for 24 hours.