What are the various types of Staircases used in building?
The stairs are classified as follows:-
(i) Straight stairs
(ii) Turning stairs
(a) Quarter turn stairs
(b) Half turn stairs
(c) Three-quarter turn stairs
(d) Bifurcated stair.
(iii) Circular or helical or spiral stairs.
(i) Straight stairs: In a straight staircase, all the steps lead in one direction. It is used for small houses where the available width is limited. The stair may consist of either a single flight or several flights with a landing. A straight staircase is sometimes called a cottage staircase.
(ii) Turn staircase: In this type of staircase, the flights turn. There are the following types of stairs:-
(a) Quarter-turn staircase: A staircase that turns around a right angle is called a quarter-turn staircase. This type of stair was commonly used in the two-story duplexes built in the first half of the 20th century because it allows for a very economical and compact design.
(b) Half-turn staircase: When the staircase turns 180°, it is called a half-turn staircase. They may be of three types:-
(1) Dog-legged Stairs: The flights of the dog-legged stairs run in opposite directions, and no space is provided between the flights in the plan. The name dog-legged is given to its appearance in section. It falls into the category of newel (or solid newel), stairs that have newel posts at the beginning and end of each flight. These are of two types such as half space landing, quarter space landing and winders. In general, the first type (i.e., without newels) is more common.
(2) Half-turn open Newel staircase: The half-turn open Newel staircase has a space or shaft between the outer stringers. This stair is used where there is sufficient space. The distance between the two stringers can vary from 150 mm to 1000 mm. If more space is available, a small staircase with two to four steps can be installed in the curve between the two quarter steps. Otherwise, if the shaft is narrow, a half landing can be provided.
(3) Geo-metrical Stairs: These stairs have no newel post and are of any geometrical shape. The change in direction in these stairs is achieved through winders. The stairs require more skills for their construction and are weaker than open newel stairs. In these stairs, the open well between the forward and the backward flight is curved.
(c) Three Quarter Turn Stair: A three quarter turn stair change its direction through 270°. In other words, direction is changed three times with its upper flight crossing the bottom one. It may either be newel type or open newel type. This type of stair is used where the length of the stair room is limited and when the vertical distance between the two floors is very large.
(d) Bifurcated staircase: this type of staircase is often used in public buildings in the entrance hall. The staircase has a wider flight at the bottom, which divides at the landing into two narrower flights, one leading to the left and the other to the right.
(iii) Circular, spiral or helical staircase
Spiral staircases have all treads radiating from a common newel post or centre point. They are made of wood, steel, or concrete and are used where available space is less. They are also used as emergency stairs and are located at the rear of a building. These stairs are not convenient.
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