Saturday, February 4, 2017

Stairs and Composing Parts of Staircases


A stair, or a stairstep is one step in a flight of stairs. In buildings, stairs is a term applied to a complete flight of steps between two floors. A stair flight is a run of stairs or steps between landings. A staircase orstairway is one or more flights of stairs leading from one floor to another, and includes landings, newel posts, handrails, balustrades and additional parts. A stairwell is a compartment extending vertically through a building in which stairs are placed. A stair hall is the stairs, landings, hallways, or other portions of the public hall through which it is necessary to pass when going from the entrance floor to the other floors of a building. Box stairsare stairs built between walls, usually with no support except the wall strings.

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Composing parts of staircases

We will be Used Below Diagram for Explained this,,
Composing Parts of Staircases

1. Staircase Shaft the walls that define the space of the staircase, it given the case.

2. Flight of stairs construction element with a slope, with /without treads, that connects more slabs or a slab and a landing.

3. Landing Horizontal construction element that allows changing of direction for the flight of stairs or, in the case of very long flights, allows people to rest on while using the staircase

4. Rail Vertical construction element (continuous or with gaps) that offers protection to the people going up and down or pausing on the (flight of) stairs.

5. Handrail Construction element from the superior part of the sill/rail and/or on the adjacent wall of the (flight of) stairs with the purpose of giving support to the people using the (flight of) stairs

6. Tread – horizontal element that allow circulation on the circulation.

7. Riser – vertical element that connects 2 treads

8. The “eye” of the staircase the free space bound by the inner parts of flight of stairs

9. Stringer The lateral or central beam going along the flight or stairs bearing all its weight .There are staircases with one or more stringers.

Stairs give us access from floor to floor. The space/room housing stairs is called staircase. Stairs consists of a number of steps arranged in a single flight or more number of flights.

The requirement of good stairs are...

(a) Width: 0.9 m in residential buildings and 1.5 m to 2.5 m in public buildings.

(b) Number of Steps in a Flight: Maximum number of steps in a flight should be limited to 12 to 14, while minimum is 3.

(c) Rise: Rise provided should be uniform. It is normally 150 mm to 175 mm in residential buildings while it is kept between 120 mm to 150 mm in public buildings. However in commercial buildings more rise is provided from the consideration of economic floor area.

(d) Tread: Horizontal projection of a step in a stair case is called tread. It is also known as going. In residential buildings tread provided is 250 mm while in public buildings it is 270 mm to 300 mm.

The following empirical formula is used to decide rise and tread: 2R + T > 550 mm but < 700 to 600 mm

whereR is rise in mm and T is tread in mm.

(e) Head Room: Head room available in the stair case should not be less than 2.1 m.

(f) Hand Rails: Hand rails should be provided at a convenient height of a normal person which is from 850 mm to 900 mm.

Types of Stairs

The stairs may be built with wood, concrete masonry or with cast iron. Wooden stairs are not safe, because of the danger of fire. However they are used in unimportant buildings to access to small areas in the upper floors. Cast iron or steel stairs in the spiral forms were used commonly to reduce stair case area. In many residential buildings masonry stairs are also used. Reinforced concrete stairs are very commonly used in all types of buildings.

Based on the shapes stairs may be classified as:

↷ straight stairs
↷ Dog legged stairs
↷ Well or open-newel stairs
↷ Geometrical stairs
↷ Spiral stairs
↷ Turning stairs

↷ straight stairs

If the space available for stair case is narrow and long, straight stairs may be provided. Such stairs are commonly used to give access to porch or as emergency exits to cinema halls. In this type all steps are in one direction. They may be provided in single flight or in two flights with landing between the two flights

↷ Dog legged stairs

It consists of two straight flights with 180° turn between the two. They are very commonly used to give access from floor to floor. Below image shows the arrangement of steps in such stairs.

↷ Well or open-newel stairs

It differs from dog legged stairs such that in this case there is 0.15 m to 1.0 m gap between the two adjacent flights. Figure 8.37 shows a typical open-newel stair.
Well or Open-newel
Well or Open-newel Stairs

↷ Geometrical stairs

This type of stair is similar to the open newel stair except that well formed between the two adjacent flights is curved. The hand rail provided is continuous.

↷ Spiral stairs

 These stairs are commonly used as emergency exits. It consists of a central post supporting a series of steps arranged in the form of a spiral. At the end of steps continuous hand rail is provided. Such stairs are provided where space available for stairs is very much limited. Cast iron, steel or R.C.C. is used for building these stairs.

↷ Turning stairs

Apart from dog legged and open newel type turns, stairs may turn in various forms. They depend upon the available space for stairs. Quarter turned, half turned with few steps in between and bifurcated stairs are some of such turned stairs.

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