Stairs

In buildings having more than one storey, stairs are provided for vertical movement of occupants between the floors. Stairs consist of a series of steps and landings that makes it possible for people to go up or down on foot with ease. Stairs are basically composed of treads, which are the flat horizontal portions of the steps, and risers, which are the vertical parts between the two steps. The projecting edge of a step which is usually rounded is called nosing. Handrails are provided at the exposed sides of a stair to prevent people from falling down, and these are supported on vertical members called balusters. Posts at the top and bottom of a stair which have to be stronger than the rest are known as newels. The enclosure containing the set of steps and landing is known as the staircase. While planning and designing stairs it is important to ensure that there is sufficient headroom, which is the minimum clear vertical distance between the tread of a step and the bottom of the flight or landing immediately above the user. Figure 6.44 shows the various parts of a flight of stairs. 

Stairs can be made from various materials like timber, bricks, stones, steel, plain concrete or reinforced cement concrete. The selection of material depends on the type of structure, availability of materials and finances available, life of a building, aesthetical considerations, fire resistance requirements, etc. 

The number of stairs to be provided in a building is dependent on the usage of the building and is generally, governed by the requirements stipulated in the local building bye laws. For public buildings the codes require at least two staircases with reference to fire safety considerations. The maximum horizontal distance from any point in a floor upto the stair is also generally stipulated and may be of the order of 30x11. The width of the stairway governs the exit capacity, and for public buildings it is about 1.8 m,  whereas for residential ones it could be 0.9 m. 

Stairs should be located such that they are easily accessible. It has to be ensured that there is sufficient light and ventilation in the staircase. 

  Elements of Stair