Section 20 in The Chennai City Corporation Building Rules, 1972
20. Stairs.
(1)All storyed buildings shall be provided with sufficient number of staircases depending on the number of occupants within a distance of not more than eighteen metres.(2)All stairs shall comply with the following requirements:-(a)Width of stairs. - The clear width of all stairways shall not be less than sixty centimetres excluding the hand rails.(b)Head room. - All stairways shall have at least two metres and ten centimetres of clear head room measured perpendicularly form the nosing.(c)Treads and risers. - (i) Treads and risers shall be so proportioned that the sum of two risers and a tread width is not less than sixty centimetres or more than sixty two and a half centimetres. No riser shall be more than seventeen and a half centimetres and no tread width less than twenty-five centimetres. There shall be no variation in the widths of treads or the heights of risers in any one flight of stairs. No window shutters of rooms adjoining a stair case shall be permitted to open in any stair way.(ii)The surface materials of stairs, treads and landings shall be such as not to involve undue danger of slipping.(d)Landings. - No stair way shall have a height of more than three metres and seventy-five centimetres between landings nor less than two risers between consecutive landings. The landings shall have a dimension not less than the width of the stairs measure in the direction of the rim.(e)Rails. - Stairs shall have walls or well secured balustrades or guards on both sides. Hand rails shall be placed not less than seventy five centimetres nor more than one metre above the nosing of the treads.(f)Space under stairs. - The space beneath any stairway built in whole or in part of combustible materials except hand rails shall be left entirely open.(g)Ventilation of stair-cases. - (i) Every stair case shall be lighted and ventilated to the satisfaction of the Engineer, from the open-space.(ii)There shall be provided a window or windows or ventilator, or ventilators of an aggregate area of at least one and a half square metre in each floor in such of the wall of the stair case room as abuts the one and three fourths metres open space to light and ventilate such stair case.This provision can be dispensed with when an open wall for light and ventilation within the space enclosed by the stair way and its landings is proposed to be provided, the least horizontal dimensions of which are equal to twice the width of the staircase:Provided that there shall be in the roof directly over each stair case a well ventilating sky light provided with ridge ventilators I or else such skylights shall be provided with fixed or movable louvers to the satisfaction of the Engineer. The glazed roof of the skylight shall not be less than three and three fourths square metres in area. No loft or any other fixture shall be erected in such stair case well.(h)Passage giving access to stair-case. - Every passage in a building in the ground floor shall in no part be less than the width of the stair case of such building to which it gives access:Provided that if only one such passage gives access to more than one stair case, its minimum width shall be equal to the width of such stair cases plus one half the total width of the remaining stair cases.
