| Top Tips
Taking Flight!
In the fourteenth of a ‘clip and keep’ series,
Engineer JAGVIR GOYAL offers more practical construction tips
on building a staircase.
1. Decide the location of a staircase carefully. A staircase
can be located inside or outside the house depending upon
the space available. If there is space, build attractive looking
stairs inside the lobby or dining room. These will add grandeur
to your house. The latest trend to make stairs look artistic
and aesthetic is by using glass and wood if they are used
exclusively by family members. A staircase built outside the
external walls of the house comes under common use —
this can be built with RCC, masonry, stone or iron.
2. Staircases can be straight-run, dog-legged, quarter-turn,
three-quarter-turn, circular, spiral, elliptical or helicoidal.
The material used can be RCC, wood, masonry, glass, stone
or iron. If you are building a small and compact house, choose
a dog-legged staircase — one that resembles a dog’s
leg! Where there is a space constraint, a spiral staircase
may be used. If your building has special architecture, use
helicoidal staircase. In all cases, keep the steps as wide
as possible.
3. Staircases commonly used in buildings have sloping slabs
from floor to floor with an intermediate landing. Provide
a 30° slope to horizontal for such stairs. In no case
should the slope be more than 40° to horizontal. The transverse
width of a step is called a tread and it should not be less
than 250 mm. The front depth of a step is called a riser and
it should not be more than 160 mm. Provide beams at the top
and bottom of each flight. The thickness of sloping slab is
called a waist and it shouldn’t be kept less than 120
mm.
4. Get the staircase designed from a structural engineer.
Generally, steps are kept 4 ft wide with the tread as 25 cm
and riser as 15 cm. All treads must be of equal width. All
risers must be of equal depth. Never vary the chosen dimensions
of tread and riser in a staircase. It may result in false
stepping and the person going up or coming down may slip down.
As a person walks a few steps, his mind automatically adopts
the riser and tread dimensions. Plan the location of the landing
carefully. Considering the total height from the top of the
lower floor to the top of the upper floor and considering
the landing as a step, the exact depth of the riser should
be worked out.
5. Provide steel reinforcement at the bottom of the waist
slab with a concrete cover of 15 mm. This reinforcement should
be taken inside the bottom beam. However, this can’t
be done at the top end. At the top end, if this reinforcement
is bent along the bottom of landing or floor, it will have
a tendency to lift off. Therefore, here, the reinforcement
should be taken to the top face of the landing or slab and
bent horizontal. To compensate its absence at the bottom face,
provide extra bars of same diameter at same spacing; take
these to the top face of sloping waist slab and bend along
the slab slope. Such a provision of steel reinforcement will
never allow the slab to fail.
6. Always provide a good headway in the staircase. It will
save the head and ease the carrying of heavy luggage up and
down. Inadequate headway defeats the very purpose of staircase.
A 6-ft-tall person should not only be able to walk straight
— even the feeling of having to bend his head to avoid
hitting the slab shouldn’t arise in him!
7. Sometimes, separate cantilever slabs for each step with
a central sloping beam are used. In such cases, the beam should
be exactly at the centre of the steps so that the two cantilever
portions balance each other. If the steps are 4 ft wide, a
beam of 1 ft width should suffice. But the depth of the beam
may work out to be quite large, in the range of 2 ft to 2.5
ft with 16 mm diameter steel at bottom. The steps should have
more thickness at the beam end and should taper to less thickness
of about 2 inch at free end; 8 mm diameter steel should be
provided in steps too. The junctions of steps with the beam
should be given fillet finish. Also, don’t forget to
provide 8 mm diameter stirrups in the beam.
8. One more style becoming popular is cantilever steps coming
out of a sidewall. Each step is independent and there is a
gap between every two steps. In this case, see that the thickness
of wall is adequate to provide required anchorage to the independent
steps. If the steps are 4 ft wide, they must have an anchorage
of at least 15 inch in the wall.
9. For a spiral staircase, provide a central pillar with
cantilever steps supported on it. Steps in such a staircase
vary in width and are called winders. Keep such a size of
the central pillar that winders have minimum possible variation
in tread width. Winders have less tread width at inner face
and more tread width at outer face. These leave a part of
the foot unsupported when walking up or down along the inner
side of staircase. Spiral staircases therefore need careful
climbing and should be chosen only if unavoidable.
10. Another popular type of stairs is the one with a tread-riser
form of slab. The bottom of such a staircase is not plain
but has the shape of steps going up. In a way, these stairs
consist of a single zigzag slab. In such a staircase, load
at each node of the tread-riser has to be worked out by a
structural engineer. The design is complex but a competent
structural engineer can handle it. In such a staircase, you
must provide steel stirrups both ways — horizontally
as well as vertically — in each step. Another striking
feature of this type of stairs is that the stirrups are of
larger diameter of steel, say 12 mm, while the steel running
along width of steps is of lesser diameter of 6 or 8 mm. Ensure
that this is the case to give required strength and stability
to stairs.
11. See that the staircase has good lighting arrangements.
Natural light is preferable. To check whether your lighting
arrangement is good, move up and down the stairs and see that
no shadows are formed. If the lighting arrangement passes
this test, it is acceptable.
12. If stairs are being provided in a lobby, try covering
them with wood. Cover full width of tread and riser of each
step. Provide double nosing of wood on treads. Provide wooden
pillars, wooden railing and wooden balustrade. A wide variety
of wooden railing pillars is available in the market. Choose
according to your taste but keep a uniform colour for the
steps and railing. Ivory Coast teak is a good wood to use
on steps and railings.
More tips will follow next month. Till then, happy building!
* The author is Superintending Engineer (Civil), author –
technical and general books, technical columnist and recipient
of the TIET Distinguished Alumni Award 2005.
| 
