A staircase is a means of providing access from the one-floor level to another. It is a means for vertical circulation.
The room or enclosure of the building where the stair is located is known as the staircase.
Necessity of staircase
1) Protect people from injury and also to facilitate access during movement from one level to another in a building.
2) Used for safe ascent or descent.
3) Also used as a means of escape in case of fire.
Components of the Staircase
The horizontal member of a stair, on which the foot is placed while ascending or descending is the tread. It is the horizontal distance between two successive risers. It is also known as the “Going”.
It is the vertical member of a stair that supports tread. The vertical distance between two consecutive treads is called “rise”.
Riser and tread together are called step.
The volume (enclosure) where the stair is accommodated is the staircase.
It is the space where the stair is housed.
Platform left between two flights for circulation and rest is landing.
Series of steps between landings is flight.
The trapezoidal tread is called winder.
The exposed edge of the tread that is projected outward is nosing.
The members receiving ends of steps are stringers.
The underside of the stair is soffit.
Minimum clear distance between the tread and the overhead structure is head room.
It is the protecting member usually parallel to the string and supports while ascending or descending.
It is the vertical infill member between the string and the handrail. A row of balusters surmounted with handrail is known as the “Balustrade”.
It is an imaginary line connecting the nosing of all tread in one flight. Pitch or slope is the angle made by the line with the horizontal.
It is the post-forming the junction of flights with a landing or carrying the lower end of strings.
Types of Staircase
Stairs can be classified under two headings:-
1)Classification based on materials
2)Classification based on shapes.
1)Classification based on materials
Based on the materials of construction stairs are as follows:-
b) Stone stair
The stairs may be built with concrete masonry, wood or with cast iron. Wooden stairs are at high risk of fire. However, they are used in unimportant buildings to access small areas on the upper floors. Cast iron or steel stairs in the spiral forms are used commonly to reduce the area of the staircase. In many residential buildings, masonry stairs are also used. Reinforced concrete stairs are commonly used in all types of buildings.
2) Classification based on shapes
Based on the shapes stairs are classified as:-
b)Well or open-newel stairs
d)Dog legged stairs
Design of the staircase
When the level difference between two floors (ceiling height plus the thickness of the floor slab) are given:-
1) Assume the types of building and stair and accordingly the size of the riser(R).
2) Find the number of risers by NR=(level difference/size of the riser).
3) Find the number of treads by NT =(NR-1).
4) Assume the size of tread (T).
5) Assume the width of the stair.
6) Consider the size of landing (L)equal to the width of the stair.
7) Assume the entry space (E), generally equal to landing.
8) Find the total length of stair =(NT*T)+L+E.
9) Adjust the size of riser and tread if required.
Salient Points to be considered in Locating Stairs
The following points should be considered in locating stairs in a building:-
(A) They must be located near the main entrance of the building.
(B) There should be easy access from all rooms without disturbing the privacy of the rooms.
(C) There should be a spacious approach.
(D) Good light and ventilation should be available.