Introduction :
The staircase is an essential component of a building providing access to different floors and roofs of the building.
It consists of a flight of steps, usually with one or more intermediate landings provided between the floor levels.
Typical Flight Of A Staircase :
Structural Components Or Terminologies Of A Staircase :
The Main Part Of Stairs:
Tread: it is the horizontal upper portion of a step where the foot restals.
Riser: the vertical distance between two neighboring steps.
Nosing: Sometimes the tread is projected outwards for aesthetic or to provide more space, this projection is called the nosing.
Flight: Flight is a series of steps provided between two landings.
Going: Going of the stair is a horizontal projection of the flight.
Landing: The horizontal slab provided between two flights. It is provided at every 10-12 steps for
comfort and is also required in case of a change of direction.
Overlap: The amount by which nosing of a tread (or landing) over sails the immediate lower tread.
Soffit: The bottom surface of a stair slab.
Headroom: The vertical distance of a line connecting the nosing of all treads and the soffit.
Waist: The thickness of the waist slab on which steps are made is known as the waist.
Stringer: These are the sloping members of the stairs, use to support the end of steps.
Winders: These are the steps used for changing the direction of stairs. These are usually triangular in plan.
Pitch or Slope: Vertical angle made by a line of nosing with vertical. Pitch should not be more than 38º.
General Guidelines For Planning A Staircase :
The following are some of the general guidelines for planning a staircase:
(i) The respective dimension of tread and riser for all the parallel steps should be the same on the consecutive floors of a building.
(ii) The minimum vertical headroom above any step should be 2 m.
(iii) The pitch should not be more than 38°.
Proportioning of Staircase :
The following components of the staircase are to be proportioned before designing a staircase.
(a) Width:
The width of a step in the staircase (width of staircase) is proportioned following the recommendations given below:
| Types of Staircase | Width of the Staircase |
|
1-1.2 m
1.2-1.6 m 1.2-2.0 m |
(b) Number of Steps:
The number of steps in a flight is usually kept between 3 and 12.
Tread is usually kept between 250 to 300 mm
Rise = 120 to 150 mm (Public building)
= 150 to 180 mm (Residential building)
Following relations are usually used to fix the riser and tread.
2R+ T = 580 to 630 mm
Rx T = 40000 to 50000 mm2
(c) Width of Landing:
The width of the landing shall not be less than the width of the staircase.