Correct Answer - Option 2 : riser minus one
Concept:
Flight: This is an unbroken series of steps between landing.
Tread: It is an upper horizontal portion of a step upon which the foot is placed while ascending or descending.
Note:
In case of flight, number of treads = riser - 1
However, general relationship between riser and tread is given by:
(2 x Riser) + Tread = Step Length
In order to make the ascent and descent easy, the treads and risers of a stair should be suitably proportioned.
Following thumb rules are commonly used for obtaining a satisfactory proportion of the tread and riser of a step:
i) (Rise in cm) + (Tread in cm) = 40 to 45
ii) (Rise in cm) × (Tread in cm) = 400 to 450
iii) (2 × Rise in cm) + (Tread in cm) = 60
iv) Take rise = 140 mm and Tread = 300 mm as standard.
The following are the components of the staircase
|
Components
|
Definition
|
|
Step:
|
It is a portion of the stair which permits ascent or descent. A stair is composed of a set of steps.
|
|
Tread:
|
It is an upper horizontal portion of a step upon which foot is placed while ascending or descending.
|
|
Riser:
|
It is a vertical portion of a step providing support to the tread.
|
|
Landing:
|
It is a level platform at the top or bottom of a flight between the floors.
|
|
Flight:
|
This is an unbroken series of steps between landing.
|
|
Rise:
|
It is a vertical distance between two successive tread faces.
|
|
Going:
|
It is a horizontal distance between two successive riser faces.
|
|
Nosing:
|
It is the projecting part of the tread beyond the face of the riser.
|
|
Scotia:
|
It is a molding provided under the nosing to provide strength to the nosing.
|
|
Soffit:
|
It is the underside of a stair.
|
|
Pitch or Slope:
|
It is the angle which the line of the nosing of the stair makes with the horizontal.
|
|
Strings:
|
These are the slopping members which support the steps in a stair.
|
|
Newel post:
|
Newel post is a vertical member which is placed at the ends of flight to connects the ends of strings and handrail.
|
|
Baluster:
|
It is a vertical member of wood or metal, supporting the handrail.
|
|
Headroom:
|
It is the clear vertical distance between the tread and overload structure.
|
