Types of Stairs

Various types of stairs are available for incorporating in the design of a building as shown in Figure : 

Straight Stairs 

In this type, there is a straight flight of stairs, with or without intermediate landings. 

Dog Legged Stairs 

This consists of two straight flights of steps with usually a level landing where the direction of traval changes by 180'. If there is constraint of space, winders, which are steps with tapered treads, i.e. triangular in plan, can be provided instead of a half landing. 

Open Well Stairs 

It consists of two or more straight flights with a central well. There could be quarter landings or winders at the comers. 

Winders are not allowed in stairs that are to be used as exits during emergencies. 

Geometrical Stairs 

This type of a stair is similar to the open well type, but instead of having quarter landings or winders at the comers the stair follows a curve with winders which are less sharp than those in the open well. 

A spiral staircase is a form of geometrical staircase, which is without a well with its steps consisting of a series of winders going round a central post. 

Size of Treads and Risers 

For convenience in performing movements, the tread should be wide enough and the risers should not be too high. Very high risers and narrow treads are difficult to negotiate. A suitable balance has to be arrived.at taking into account the cost and comfort. Some of the thumb rules to obtain proper tread (cm) and riser (cm) dimensions are listed as under : 

1. The product of riser height and tread width should be between 450 and 480. 
2. Riser height plus tread width should range between 43 and 45. 
3. The sum of the tread width and twice the riser height has to be 61 to 64.