Design of stair

A stair is a set of steps leading from one floor of a building to another, typically inside the building.
The room or enclosure of the building, in which the stair is located is known as staircase.
The opening or space occupied by the stair is known as a stairway.
Types of stairs used in building construction is broadly based on the shape of the stairs.
Straight stairs, Turning stairs and Continuous stairs are broad types of stairs.
The width of the landing should not be less than the width of stairs
Width of stairs
Residential:-0.9 to 1 m
Public :- 1.8 to 2 m
Tread
Residential:-220-250 mm
Public:- 250-300mm (not less than 200mm in any case)
Riser
Residential:-150-180 mm
Public:- 120-150mm (not more than 200mm in any case)
Pitch
Should not be more than 38°
Head room clearance
Should not be less than 2.1m
No of steps should be minimum 3 and maximum 12
All the steps on the same flight must be identical
When possible, use of straight stair flights should be preferred
Geometrical design
Assume suitable tread and riser
No of riser= (f/f height) ⁄ rise
No of risers in one flight=0.5×(no. of risers)
No of tread = (no of risers - 1)
Going distance= (no of tread) × (tread width)
Width of landing ≥ width of stair
Common relation…
G + 2R ≈ 60 cm
G X R ≈ 400-410 cm2
Most commonly adopted values….
For residential building….
R = 16 cm & G = 25 cm
For public building….
R = 13-15 cm & G = 27-30 cm