CLASSIFICATION OF STAIRS BASED ON MATERIALS OF CONSTRUCTION General materials used in construction of stairs are
o Wooden
o Stone
o Brick
o Metals/steel
o Plane concrete o RCC
• Wooden stair
o As they are light in weight, mostly used for residential building.
o The main objection to this stair is that it is easily attacked by fire and
thus, in fire, the occupants of upper floor can’t escape.
o If it is made from good timber like Teak, and thickness is about 45mm, it becomes sufficiently fire proof and allows enough time for occupants
on upper floor to escape. Factors to be considered here are,
• Metal Stair
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o o o o
The string supporting ends of wooden steps may be a cut string/closed string.
Scotia blocks may be provided to give additional finish to wooden steps.
Small triangular wooden blocks called glue blocks may be provided at inner angle formed between a trade and riser, to provide additional strength.
A metal strip may be provided on nosing of wooden step to increase its resistance against wear and tear.
The landing may be formed by providing wooden beams of suitable sizes.
Sometimes risers are omitted. trades are housed in strings and soffit is covered with wooden battens/metal sheets.
The timber used should be free from fungal decay, insect attack, or any defect. Edges may be finished smooth and excess light timber should not be used.
They are not frequently/commonly used stairs.
The external fireescape stairs are generally made of metal. Common metals are CI, bronze, and mild steel.
Widely used in factories, workshop, and godowns.
Main features are,
? Stringers are usually of channel section
? Tread and riser of a step may be of one unit or may not
be
52 * Under revision
? Tread and risers are supported on angles, which are connected to stringers.
? Risers may be totally omitted.
? Spirals stairs of CI consists of CI newel fixed in center
around which the CI steps are fixed.
? For metal stairs metal balusters with pipe handrail are
used.
• RCC Stair
o Commonly used in all type of construction.
o They resist better fire and wear than any other material and can be moulded to desired shape.
o The step can be provided with suitable finishing material such as marble, terrazzo, tiles etc.
o They can be easily maintained, strong, durable and pleasing in appearance.
o They can be designed for greater widths and layer spans. o The steps may cast in situ/pre cast.
o It is possible to pre cast a flight and place it in position by
equipments.
The materials can be used together/combination with each other to form COMPOSITE STAIRS.
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