The properties of a good staircase
Stairs should be set up in such a manner that the people can access them from the various rooms of the building.
In stairs there should be provision for sufficient light and proper ventilation.
The width of the stair should be sufficient to accommodate lots of persons in busy hours or emergencies. Normally, for interior stairs, the clear width is necessary to be minimum 50 cm in one and two family dwellings, 90 cm in hotels, motels, apartment and industrial buildings and 1.1 m for other types of residence.
Normally, the number of steps in a ?ight should remain limited to and a minimum of 3.
Sufficient headroom should be arranged to safeguard tall people from wounding their head. Vertical clearance should never be under 2.15.
Sizes of risers and treads should normally be uniform from the comfort point of view. Treads should be 25-325 cm wide, apart from nosing. Treads under 25 cm width should contain a nosing of about 25 cm. The most suitable height of the riser is 17.5-18.5 cm. Usually, the following formulae is applied.
410. The product of riser and tread should remain among 400 and 410.
411. Riser plus tread should be equivalent to 42.5 - 43.5 cm.
412. Sum of the tread and twice the riser should remain among 60 and 64cm.
Stair width is based on the objective and concern of the building. For residential buildings, it should be maintained as 1m.
The required number of stairways should be dependent on the maximum ?oor area contributory to a stairway. The number of persons to be accommodated by stairs each ?oor per 55 cm unit of stair width should remain 15 for such buildings as hospitals and nursing homes, 30 for other institutional and residential buildings, 45 for storage buildings, 60 for mercantile, business, educational, industrial buildings, theatre and restaurants, 80 for churches, concert halls and museums, and 320 for stadium and amusement structures.
The lowest width of landing should be similar to the width of the stairs.
The highest and lowest pitch should remain 40?and 25? mutually in any stairs.
If it is necessary, winders should be arranged at the lower end of the ?ight. Normally, the winders in a staircase should not be used.
Balustrade should be arranged in open-well stairs to get rid of the danger of accidents.
The proposed live loads on stairs is indicated by IS:87S-1964. The stairs and landings are designed for a live load of 300 kg/mi in buildings where no overcrowding occurs. For public buildings and warehouse, where there is possibility of overcrowding, the live load may be accepted as 500 kg/m2.