The stair is a structure having a series of steps and affords the means of ascent and descent between the floors or landings. The enclosed room in which stair is located is known as the staircase. The opening space occupied by the stair is known as a stairway.
A stair consists of treads, risers, stringers and balusters and so many other connected elements. Stair may be made from timber, stone, bricks, steel, plain cement concrete or reinforced cement concrete. following are the requirements of good stairecase:
It should be located centrally so easily accessible from every corner of the building. Light and proper ventilation should be there.
Width of the stair
The usually adopted average value of the stair width for public and residential building is 1.8 m and 90 cm respectively.
Length of flight
Number of step in flight should be restricted to a maximum of 12 and a minimum of 3.
Pitch of the stair
The slope of the stair should never exceed 40°C and not be flatter than 25°C.
The headroom of the flight immediately above it should not be less than 2.14 m.
It should be strong durable and stiff. The materials by which stair is constructed should possess fire-resisting qualities.
The width of the landing should not be less than the width of the stair.
The rise and trade of each step in stair should be of uniform dimensions throughout.
The height of the riser should not be more than 20 cm.
It should be provided with handrails.
Winder step as for as possible should be avoided.
The Proportion of Trade and Riser
The size of trade and riser varies with the situation of the stair and the purpose for which it has to be provided. In general, the following thumb rules are considered.
1. (Going in cm) + ( 2 x Rise in cm) = 60
2. (Going in cm) + (Rise in cm) = 400 to 410 approx
3. Adopt the standard size going and rise as 30 cm and 14 cm respectively and for each 25 mm deducted from going and 12 to 13 mm to rise.
The results which are practically adopted in the stair constructions are
1. For Residential Building – 25 cm x 16 cm
2. For Public Building – 27 cm x 15 cm to 30 cm x 13 cm
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