Stair is a series of steps or flights of steps for passing from one level to another. It is a set of steps leading from one floor of a building to another, typically inside the building.

1. Geometric Stair

A winder stair in which the outside of the winders is supported by walls forming three sides of a rectangle, and the inner side is unsupported and without a newel post.. It is a continuous stairs that turn or wind about a central well hole which has rounded corners or is circular or elliptical and that have the strings and rails arranged upon geometric principles and running continuously from top to bottom.

2. Quarter turn stair

A quarter-turn staircase consists of two straight rows of stairs and a one quarter turn of 90°. With this type of staircase, from the base to the top, the steps and the person on them turn 90°.

3. Bifurcated stair

This type of stair is commonly used in public buildings at their entrance hall. The stair has a wider flight at the bottom, which bifurcates into two narrower flights, one turning to the left and the other to the right, at the landing. It may be either of newel type with a newel post as shown in figure 9 below left side or of geometrical type, as shown in the right portion of the figure with continuous stringer and hand rails.

4. Circular stair

A circular staircase rotates in a round fashion around the circumference of a given area. Usually turns more than 90 degrees. This stair has a center “hole” that a person can look up or down through. Sometimes people hang chandeliers through the center area of these stairs.

5. Spiral stair

A spiral staircase is a structure that is built around a central post that acts as an axis for its steps. The origin of this type of staircase dates back to the Middle Ages. They were used both for aesthetic purposes and for defense.