Building Technology Staircases Notes

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STAIRS
Definition:
A stair is a series of steps leading from one level to another
Functions:
1. To provide movement between different levels
2. For access from floor to floor
3. For escape iron upper to lower floors (levels) in the event of fire
Functional requirements of stairs:
1. Stairs should be strong and stable to carry loads (of people,
furniture etc)
2. A stair should be fire resistant-in order to maintain its structural
integrity and to prevent spread of fire from one floor (level) to
another.
3. They should have good sound insulation.
Stair terminology:
1. Step - A short horizontal surface for the foot to facilitate movement
from one level to another. It consists of a tread and a rriser.
2. Tread - Horizontal face of the step
3. Riser - Vertical/ nearly vertical face of step
4. Noising - This is the projection of the tread beyond face of risers
5. Line of noising - An imaginary line which touches all the noising in
a flight. It is also called the pitch line.
6. Fight - An uninterrupted series of steps between floors or between
floors and landing or between landing and landing
7. Landing-1t is a horizontal platform between two flights. The
purpose of a landing 1s for change of direction, and for break of flight.
8. Rise - The vertical distance between the top surface of two
consecutive treads. The total rise of a stair is a vertical distance
between the top and bottom treads.
9. Going - Horizontal distance between the top and bottom noising.
10. Stairwell / way - A hole formed in a floor which accommodates a
stair. The term "well" also refers to the Space (on plan) between the
outer strings of a geometrical or open newel
11. Stair case - The complete stair structure including fights,
landings, balustrades etc, and also that part of the building which
encloses the stairs.

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12. Srtings - The main inclined members (in case of a timber stair)
which Carry the steps. They are sometimes referred to as stringers.
A "wall" string is adjuscent and fixed to a wall
An "outer" string is boused to enclose the steps/treads.
A 'cut sting has its top edge cut to the shaped of the steps
13. Balustrade/railing - A barrier comprising of newels, handrails,
and infill which protects the open side of the stairs or landing.
14. Balusters – Upright members forming the infill between strings
and handrails in balustrades.
15. Pitch/Slope - the angle between the line of nosing and the line of
the floor/landing.
16. Hand rail – inclined rail, usually moulded, serving as an aid to
climbing or descending a flight and also acts as a guard rail.
17. Carriage or carriage piece. An inclined bearer, parallel to the
strings fixed below the stairs as an intermediate support to the steps
of a wide flight. It is usually a rough piece of timber.
18. Scotia - A concave moulding fixed to the steps of a wide flight.
19. Newel/ Newel Post – A heavy vertical member into which the
strings and handrails are fixed
20. Head room – The minimum distance measured vertically from the
lining of nosing (or landing) to the ceiling above.
21. Pitch board - A template used for setting out purposes which
contains the rise and going of one step.
22. Margin-The portion of a closed string, parallel to its top edge into
which the noisings project.
23. Storey rod - A lath of timber, the length of which represents
exactly the total rise of a stair. The measurement is usually taken on
site on the actual rod; from floor level to floor level i.e. one storey. It is
ssubsequently divided into the number of steps in the stair
24. Open- riser stair-A stair without risers. It is also variously known
as open tread and ladder stairs.
25. Cap:- The shaped top of a newel past. it may be worked on the
solid newel or planted, in which case it is known as a "loose” cap. A
similar shape, worked or planted on the lower end of a newel which
projects below the ceiling is known as a “drop”
26. Winders - These are tapering steps used for changing the
direction of stairs.
27. Soffit -The underside of the stair.

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Design requirements of stairs
i) Each flight should have equal steps to permit regular movement
ii) Headroom shouldn't be less than 2m.
iii) Pitch should be 25o – 42o
iv) It should be large enough to accommodate people by passing one
another.
v) Each stair should be provided with a handrail
vi) A flight should contain a maximum of 16 steps.
Dimensions:-
The heights of steps shouldn't be too high because the effort needed
liftt the foot increases with the height it must be raised. Shallow steps
are labourious since more steps are needed to achieve a certain
height.
In private stair ways, e mise shall be 225 - 200 (maximum) and the
goingshall be 210- 225 (min).
In common stair ways, the maximum rise is 190 mm and the going
230mm (min)
Semipublic (Factories, offices, shops): Going 250 – 275, rise 165 – 190
Public (Assembly halls, churches, stadium): going 280 – 300, Rise 150
– 180

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Location of stairs:
Stairs should be located in an area within the building that has
sufficient light and ventilation.
Classification
1. A straight stair – it is used to provide access to an entrance or
porch. All the steps run/rise in the same direction. The flight
may be broken by a landing if the ascending is steep.
2. Dog legged stair / half turn:
This consists of two straight flights of steps with an abrupt turn
between them. A level landing is placed across the two flights at the
change of direction. This type of stair is used where the width of the
stair case hall is just sufficient to accommodate two widths of stairs

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3. Open newel stair / quarter turn:
This consists of two or more straight flights arranged in such a way
that a clear space called a well occurs between the backward and
forward flights.
4. Geometrical Stairs:
This is similar to the open newel stair, with the difference that
connection between the forward and the backward flights is
curved.
5. Circular stair:
These stairs, when viewed from above appears to follow a circle with
single centre of curvature and large radius. They are commonly
provided at the backside of a building for providing access to its
various floors for service purposes. All the steps radius from a
newel post in the form of winders. They can be constructed by
stone, steel, or reinforced concrete.

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6. Spiral Stairs
These are similar to circular stairs, exceptthat the radius, of
curvature is small and the stairs may be supported by a centre
post, overall diameter of such stairs may range from 1 – 2.5m

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7. Bi- furcated stairs
This is provided in modern public buildings. The flights are
arranged in such away that there is a wide flight at the start, which
is sub-divided into two narrow flights at the mid-landing, starting
at each side of the mid-landing
Construction of stairs:
1. Wooden stairs:
Wooden stairs are used where resistance is not of much consideration.
Timber stairs are cheap, light in weight, easy to construct and
maintain.
They can be either built in place or they can be shop fabricated.
The man disadvantage is that in the event of fire, the occupants of
upper floor find no way to escape.
The timber used should be free from fungal decay, insects other
defects.
Open riser stair has no risers, just the treads are their support. This
form
of construction while forming an interesting architectural feature also
facilitates a more even distribution of heat and light. It also makes
cleaning easier.

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Steps the thickness of the tread shouldn’t be less than 22mm (its
common to adopt 38am as the thickness). In closed riser stair, risers
are at least 25mm thick and are connected by nailed/screwed tongue
and grooved joints to the treads.
Stringers- These are slopping wooden members, providing support for
the steps (32-50 x 25 - 38)mm.
Landings:-
They are made of tonued and grooved boarding on joists supported on
the wall.
2. Reinforced concrete stairs:
They predominate stairs made out of wood, stone etc because of their
advantages over those materials. It's the most suitable of all materials
the stars can be moulded in any desired form to suit any architectural
requirement.
They can be pre-cast or cast in situ. They are often covered with thin
slab of stone, terrazzo, cement sand screed. In order to prevent the
nosing getting cracked or knocked off, it should be protected by angle
metallic strips.

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Other means of vertical transportation in buildings
1. Elevators or lifts
Elevators are used in buildings having more than four storeys. They
are used tor providing vertical transportation of passengers or freight.
They can be electric or hydraulic. Electric traction elevators are used
exclusively in tall buildings. Hydraulic elevators are generally used for
low rise freight service which rise up to six storeys.
2. Ramps
These are sloping surfaces used to provide an easy connection
between floors. They are especially useful when large number of
people or vehicles have to be moved from floor to floor. They are
usually provided at places such as garages, railway stations,
stadiums, townhalls office buildings exhibition halls and hospitals.
Sometimes they are provided in special purpose buildings such as
schools for physically hand capped children.
They should be constructed with a non- slip surface. They are given a
slope of 100 -150
The main disadvantage with ramps 1s that they require more space for
their construction.

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3. Escalators
These are power stairs. They are used when it is necessary to move
large number of people from floor to floor. These stairs have
continuous
operation without the need for operators. They have large capacity
with low power consumption.

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Course work to be Handed in on 11th April 2022
Answers shall be on separate sheets of paper, not in your note books
1 a) Define the following terms as used in stair construction
i. Tread
ii. Line of nosing
iii. Balustrade
iv. Headroom.
v. Rise.
vi. Pitch
b) What is a straight flight as used it stair construction and when is it
necessary for a straight flight to have a landing?
c) Describe the constructional procedure of timber stair construction
and show the following.
i. Method of fixing together the treads and risers
ii. How the steps are fixed to their stringer
2 a) Distinguish between:
i. private stairway and common Stairway
ii. Straight Right stair and doglegged stair
(b)
i. Give five building regulations governing the construction of
stairways
ii. Sketch parts of a wooden stair and name any five members.
iii. What is the difference between a landing and a going of a
stair.
3.a)Explain the following terms as applied to stair construction
i. Stair case.
ii. Baluster
iii. Geometrical star.
iv. Going
v. Hand rail
vi. String
b) Sketch a cross-section through two steps and land of a reinforced
Concrete stair and on it show: -
i. Landing beam and its sizes.
ii. Landing and its length as required by building regulations.
iii. Metal baluster and handrail.

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4. Sketch a cross-section through two steps of a wooden stair and on
it lable
the following parts.
i. Margin
ii. Stinger.
iii. Tread
iv. Line of nosing
v. Wedges.
vi. Going
vii. Riser
3. a) Explain the difference between a stair and a flight.
(b with aid of a neat diagram, describe the following types of stair
cases
i) Quarter turn stair
ii) Half Turn stair
iii) Bifurcated stair
iv) Newel stair