This document provides specifications for RCC roofing, including: 1) There are general specifications for different classes of buildings and detailed specifications covering materials, mixing, laying, curing and finishing of concrete. 2) Reinforcing steel must be free of corrosion and defects, bent according to design, and have the proper concrete cover. 3) Proportions, mixing, placing, compacting and curing of concrete are specified to ensure a dense, durable concrete roof structure.

1. RCC ROOFING
SUBMITTED BY:
AAKRITI SHARMA
GURPREET SINGH
JOGMAN
KOMALPREET

2.  There are two types of specification :
General:
• First class building: R.C.C. slab roofing with an insulation layer and
lime concrete terracing above (height >3.7m)
• Second class: Roofing shall be of R.B. slab
• Third class: Brick roofing.
• Fourth class: Tile roof with wooden supports
Detailed:
• Steel
• Centering & Shuttering
• Proportion of cement concrete
• Materials for concrete
• Mixing
• Laying
• Curing
• Finishing
• Measurement

3.  Steel reinforcement bars shall be of mild steel or deformed steel and
shall be free from corrosion, oil, grease, etc.
 The steel bars shall be round and capable of being bent without
fracture
 Bars shall be hooked and bent and placed as per design.
 They shall be bound together tight with 20S.W.G. annealed steel wire
at the point of intersection.
 Bars shall be bent cold by applying gradual and even motion, bars of
40mm dia. and above may be bent by heating to dull red and
allowing to cool slowly.
 Joints should be avoided.
 Bigger diameter bars should be joined by welding.
 While concreting steel bars shall be given side and bottom covers of
concrete by placing precast, blocks underneath of 1:2 cement mortar
2.5cm x 2.5cm in section and thickness of specified cover, 4cm to
5cm for beam and 1cm to 2cm for slab.
 During laying and compacting of conc. The reinforcement bars should
not move from their position.

4.  This should be maid with timber or steel plate closed and tight to
prevent leakage of mortar(with props, bracing and wedges).
 No plastering should be made on conc. surface.
 A court of oil washing should be applied over shuttering to have
smooth and finish surface.
 For slab and beam small camber should be given in centering,
1cm per 2.5 m with a max. of 4cm.
 Centering and shuttering should not be removed for 10 days for
roof slab and 14 days for beam.

5.  PROPORTIONS- cement conc. 1:2:4 by volume for slabs,
beams, lintels unless otherwise specified.
 MATERIALS- coarse aggregate shall be of hard broken
stone of granite or similar stone free from dust, dirt and foreign
matters. The stone aggregate shall be 20mm to 5mm. Fine
aggregate shall be of coarse sand consisting of hard, soft and
angular grains and shall pass through screen of 5mm square
mesh. Sand shall be free from dust, dirt and organic matter.
Cement shall be fresh portland cement of standard ISI
specifications and shall have required tensile and compressive
stresses.
 MIXING- mixing is of following types:
1. HAND MIXING- it shall be done in masonary platform or sheet
iron tray. The entire mixing is done by the worker himself.
2. MACHINE MIXING- the mixing is done in the cement conc.
mixer to have the required proportions. Output of conc. Mixer is
15-20 mix per hour.

6.  Before laying the conc. Shuttering shall be clean, free from dust,
dirt and other foreign matters.
 Conc. shall be deposited in its final position.
 Care should be taken that the time between mixing and placing
of conc. Shall not exceed 20 mins. so that the initial setting
process is not interfered with.
 Conc. shall be compacted by mechanical vibrating machine until
a dense conc. is obtained.
 Compaction shall be completed before 30 mins of addition of
water to dry mixture.
 Conc. Shall be laid continuously, if laying is suspend for rest or
the following day, the end shall be sloped at an angle of
30degree and made rough for for future joining.

7. CURING –
 After about 2hrs. when the conc. begins to harden, it shall be kept
damp by covering with wet gunny bags or wet sand for 24hrs. , and
then cured by flooding with water making mud walls 7.5cm high or
by wet sand.
FINISHING –
 The exposed surface shall be plastered with 1:3 cement sand
mortar not exceeding 6mm. and the plastering shall be applied
immediately after the removal of centering while conc. is green.
( surface of the conc. is wetted and neat cement wash is given
before applying plaster)
MEASUREMENT –
It shall be taken in cu m or cu ft. The rate for RCC work shall be for
the complete work excluding steel but including centering and
shuttering and of all tools.