Unit 11 Building

1. Unit-11:
Stairs and Roofs
Stairs and Roofs

2. Introduction
A stair is a series of steps arranged to connect different floors of a building. The
space or room housing the stair is called staircase.
Location of stair
In public building it should be located near the main entrance and in residential building it
should be placed centrally so as to provide easy access from all the rooms and to maintain
privacy at the same time.
Types of stair
Different forms of stairs may be classified as follows:
1. Straight Stairs:
Generally for small houses, available width is very retractable. So, this type of straight stairs
are used in such conditions which runs straight between two floors. This stair may consists
of either one single flight or more than one flight with a landing.

3. Types of stair
It consists of two straight flights of steps with abrupt turn between them. Usually,
a level landing is placed across the two flights at the change of direction. This type
of stair is useful where the width of the stair-case hall is just sufficient to
accommodate two width of stair.
3. Open-newel Stairs:
It consists of two or more straight flights arranged in such manner that a clear space called a
well occurs between the backward and the forward flights. If the width of the stair case hall
2. Dog-legged Stairs:
well occurs between the backward and the forward flights. If the width of the stair case hall
is such that it becomes difficult to accommodate the number of steps in the two flights,
without exceeding the maximum allowable limit of steps in each flight, a short flight of 3 to
6 steps may be provided along the width of the hall. In this state, the intermediate short
flight will have quarter space landing on its either side.
4. Geometrical Stairs:
This is similar to the open-newel stair with the difference that the open well
between the forward and the backward flight is curved. In this form of stair, the
change in direction is obtained through winders.

5. Types of stair
Circular stair is commonly provided at the backside of a building for rendering
access to its various floors for service purposes. The circular stairs are commonly
constructed in RCC, cast iron or stone. In this form of stairs all the steps radiate
from a newel post or well hole, in the form of winders.
6. Bifurcated Stairs:
This types of stair is provided in modern public buildings. In this type of stairs, the flights are
so arranged that there is a wide flight at the start which is sub-divided into narrow flights at
5. Circular Stairs:
so arranged that there is a wide flight at the start which is sub-divided into narrow flights at
the mid-landing. The two narrow flights start from either side of the mid-landing.

8. Technical terms used
1. Stairs. Stairs are steps arranged in series for the purpose of an assess from one floor
to the other.
2. Stair-case. The room or apartment in which stairs are enclosed, is called stair-case.
3. Rise. It is the vertical distance between the two conse-cutive steps. The vertical
portion of the step is called
4. Tread. The horizontal portion of the step is called tread. The horizontal distance
between the two consecutive risers is called Go, Going or Run.
5. Nosing. It is the front edge of the tread which projects beyond the riser.
6. Fliers. The rectangular steps of uniform shape and size are called Fliers.
7. Winders. The triangular or wedge shaped steps, used for changing the direction are
7. Winders. The triangular or wedge shaped steps, used for changing the direction are
called winders.
8. Flight. It is a continuous series of steps in one direction,, separated by horizontal
platforms or winders.
9. Landing. It is the horizontal platform provided at the top-of a flight. If the landing is
of a rectangular shape, having a length equal to twice the width of the stairs, the
landing is called Half Space Landing. If on the other hand, the stairs run at right angles
to each other and are separated by a square landing, the landing is-called Quarter
Space Landing.
10. Line of nosing. It is the imaginary line joining the ends of nosing of all the steps.

9. Technical terms used
11. Scotia block. It is a triangular wooden block used below the nosing to give
it additional strength.
12. Strings or stringers. These are inclined members which support the steps.
13. Headroom. It is the vertical distance between the line: of nosing and this
under surface or ceiling of the stair-case or the next flight.
14. Line of walking. The tendency of a person going on the stair is to walk
along a line which is nearly 45 cm from the centre of the hind rail. This
imaginary line is called Line of walking.
15. Railing. This is a moulded block of wood or some other material, provided
15. Railing. This is a moulded block of wood or some other material, provided
to afford assistance and safeguard to persons while going on the stairs. The
height of a railing should be nearly-75 cm above the line of nosing.
16. Balusters. These are short vertical members which support the hand-
railing.
17. Balustrade or Banister. The composite member c insisting of a hand rail,
balusters, newel posts is called balustrade.
18. Newel posts. These are principal balusters used at the ‘top and bottom of
a flight.
19. Pitch or slept. It is the angle which the line of nosing of the stairs makes
with the horizontal.
20. Soffit. It is the under surface of a stair.

10. Technical terms used

11. Requirements of good stair
Location: The following points should be considered for locating stairs in building:
• They should be located near the main entrance of the building.
• There should be easy access from all rooms without disturbing the privacy of
rooms.
• Approach should be spacious.
• The stairs should have good light and ventilation.
Width: Commonly required width in residential building is 0.9 m, while it is 1.5 to
2.5 m in public buildings.
Number of steps in a flight: The maximum number of steps in a flight should be
limited to 12 ( in some cases up to 14), while the minimum is three.
limited to 12 ( in some cases up to 14), while the minimum is three.
Rise: Rise provided should be uniform. It is normally 150 to 175 mm in residential
buildings, while in public buildings, a rise of 120-150 mm is preferable. However,
in commercial buildings, greater rise is provided to make the construction
economical.
Going: In residential buildings, a going of 250 mm is provided, while in public
buildings it is 270-300 mm. The following empirical formula is used to determine
the rise and goings:
2R + G > 550 but < 600 to 700 (all units in mm)
Head Room: Head room in staircase should not be less than 2.1 m.
Handrails: Should be at height of 850-900 mm.

12. Numerical:
1. Draw the geometric design of stairs for an office building in a room measuring
3.3 X 6.3 m. The vertical distance between the floors is 3.6m.
2. Draw the geometric design of an RCC stair for a hospital with a staircase of
internal dimensions 6.0 X 4.5 m. Floor to floor height is 4.2 m.

13. Thank You!!!!!!
Thank You!!!!!!