STAIRS 1

TIMBER STAIRS - METAL STAIRS

1. T
IMBER STAIRS
„
A staircase with treads and risers constructed from
timber
boards
from
timber
boards
.
„
Timber stairs are comparatively light in weight and
easy
to
construct
and
easy
to
construct
.
„
The timber used for the construction should be free
from
fungal
decay
and
insect
attack
and
free
from
fungal
decay
and
insect
attack
,
and
shouldbewelltreatedbeforeuse.
„
Major
limitation
:
„
Major
limitation
:
„
Poor fire resistance ; fire resisting hard wood (such
as
teak
oak
mahogany
etc
)
of
proper
(such
as
teak
,
oak
,
mahogany
etc
.
)
of
proper
thicknessofabout45mmmaybeusedwhichis
sufficientl
y
fire-
p
roo
f
.
y
p

2. COMPONENTS
„
The members of the
staircase fli
g
ht arestrin
g
s
,
g
g,
treadsandrisers.
„
The strin
g
sarethesu
pp
ort
g
pp
for the stairs and act as
inclined beam spanning
between the floor and the landing landing
.
„
The treads and risers are joined
to
form
the
steps
of
joined
to
form
the
steps
of
the flight and are housed in or fixed to strings whose p
ur
p
ose is to su
pp
ort them.
pp
pp
„
For additional support, a bearer or a carriage may be placed
under
the
treads
(In
normal
practice,
one
bearer
is
provided
for
a
under
the
treads
(In
normal
practice,
one
bearer
is
provided
for
a
90 cm wide staircase, and an additional bearer for every 40 cm of
width.)

3. TimberStairs
T
he members of the fli
g
ht are usuall
y
cut from the
g
y
timbersofthefollowingsizes:
Treads32or38,Risers19or25,Strings38or44.

4. Timber steps:
„
The thickness of timber step
(tread) should not be less
than
32
mm
and
that
of
riser
than
32
mm
and
that
of
riser
25 mm.
„
Timber tread and riser can be simply
joined
by
tongue
and
simply
joined
by
tongue
and
grooved joints. The joints are then nailed or screwed.
•The nosing of the step should not project beyond the face of the riser
for more than the thickness of the tread.
•Scotia block may be provided to improve the appearance of the steps. •The small triangular wooden blocks, known as the glue blocks, may be provided at the inner angle formed between a tread and a riser, to give provided

at

the

inner

angle

formed

between

a

tread

and

a

riser,

to

give

additional strength to a wooden step. These blocks are glued and placed
at about 80 mm distance.
•
A metal strip may be provided on the nosing of a wooden step to
•
A

metal

strip

may

be

provided

on

the

nosing

of

a

wooden

step

to

increase its resistance against wear and tear.

5. Joiningriserstotreads
:
The usual method of joining
risers to treads is to cut tongues
on the ed
g
es of the risers and fit
g
them to grooves cu
t
in the
treads.
The tread of the stair tends to
bend under the weight of people
using it. When a tread bends the tongue
on the bottom of the riser comes
out
of
the
groove
in
the
tread
out
of
the
groove
in
the
tread
and the staircase ‘creaks’. To prevent this it is a common p
racticetosecurethetreadsto
pthe risers with screws.
Nosingontreads
:
Nosing

on

treads
:
The nosing on treads usually projects 32, or the thickness of the tread from the
face of the riser below.

7. „
Angle blocks: After
the
treads
and
risers
have
After
the
treads
and
risers
have
been put together and glued and
wedged
into
their
housings
and
wedged
into
their
housings
in the string, angle blocks are
glued in the internal angles
between the underside of treads and risers and treads and risers and
string
and
string
.
Angle
blo k
e
tingl
A
ng
le
bl
oc
k
sare
t
r
iangu
lar
sectionsofsoftwood.
Their purpose is to strengthen the
right
-
angled
joints
between
the
right
angled
joints
between
treads,risersandstrings.

9. „
Winders:
„
In narrow stairs, the treads of winder steps are supported on risers which
act
as
cantilever
beams
fixed
in
the
staircase
wall
.
In
such
which
act
as
cantilever
beams
fixed
in
the
staircase
wall
.
In
such
cases, the riser should be of sufficient thickness to perform the
function of a cantilever beam. At its free end, the cantilever riser
beam is housed into the newel
p
ost. For wider stairs the winders are
p
supported by means of bearers built into the wall at one end and framed and housed into the newels at the other. The back of the barer is rendered flush with that of the riser immediatel
y
over it.
y

10. „
Landings:
„
A
landing
is
constructed
of
„
A
landing
is
constructed
of
tongued and grooved
boarding on timber joists
which are supported on walls.
h
f
hlf
In t
h
ecaseo
f
h
a
lf
space
landing, a timber joist is
placed in the wall at one end
and
housed
with
the
newel
at
and
housed
with
the
newel
at
the other end.
„
Half turn landing:
A
half
turn
landing
is
A
half
turn
landing
is
constructed with a sawn softwood trimmer which supports sawn softwood ldi
jit
b
d
lan
di
ng
j
o
is
t
sor
b
earers an
d
floor boards.
„
Newel posts:
Th
l
t
t
f
Th
enewe
l
pos
t
sarecu
t
f
rom
100 X 100 timbers and
notched and bolted to the
timber timber
.

12. St
rin
ge
r
s
St ges
„
Stringers are employed to provide support for the steps. Stringsareinclinedwoodenmembers32to50mmthick Strings

are

inclined

wooden

members

32

to

50

mm

thick

and 25 to 38 cm deep. They are supported on newels,
trimmin
g

j
oists or
p
itchin
g

p
ieces.
gj p gp
„
The thickness of strings may be 3to5 cm and depth may b
b
2
0
b
e
b
etween
2
5to4
0
cm.
St i
b
f
f
t
„
St
r
ingersmay
b
eo
f
f
our
t
ypes:
–Cutstring
Housed
string
–
Housed
string
–Roughstring –
Wreathed
string
Wreathed
string

13. 1
)
Cut Strin
g
:
)
g
It is stringer with its upper surface having carriages or houses accurately
cut to receive the treads and risers and the lower edge being parallel to
the pitch of the stair. It is considered that the appearance of stair is improved by use of cut-strin
g
, but it has the disadvanta
g
e of weakenin
g
the string as deep cuts have to be made in it.

14. 2) Housed or closed
string: string: It is a stringer having its
top and bottom edges
parallel
to
the
slop
of
the
parallel
to
the
slop
of
the
stair. It has grooves cut on its inside to receive the treads and risers of the steps. The treads and risers of the steps. The treads and risers are usually nailed,
g
lued and
wedged to the stringer.

15. Cut Strin
g
Housed or closed string
g
Housed

or

closed

string
3) Rough String:
Rh
ti
it d d
i
id
ti
f
th
f
R
ou
gh
s
t
r
in
g
ers are
in
t
ro
d
uce
d
inw
id
er s
t
a
irs
f
or
th
e purpose o
f
rendering intermediate support to the steps.
4) Wreathed string:
It
is
curved
or
geometrical
stair
string
It
may
be
of
cut
or
closed
It
is
curved
or
geometrical
stair
string
.
It
may
be
of
cut
or
closed
type.

17. Open Balustrade:
Traditional balustrade consists of
newel
p
ost
,
handrail and timber
p,
balusters.
Handrail
the to
p
of the handrail is usuall
y

py
fixed at a minimum height of 840
vertically above the line of nosing
for domestic stairs in a single house and 900 for all other stairs house

and

900

for

all

other

stairs
.
Balusters
they may be 25 or 19 square or
moulded They are either tenoned moulded
.
They

are

either

tenoned

or housed in the underside of the
handrail and tenoned in to the top
o
f
c
losed

s
trin
gs

o
r
se
t int
o

ocoseds gsose o housings in the treads of flights with cut strings.

18. „
Closed balustrade:
The space between the handrail and a
close
string
can
be
enclosed
with
timber
close
string
can
be
enclosed
with
timber
panels, plywood, hardboard, glass or
any sheet material fixed to a light
framewor
k
.
„
Spandrel:
the triangular space between the
underside
of
the
lower
flight
of
a
stair
underside
of
the
lower
flight
of
a
stair
and the floor is the spandrel.
„
Carriage:
A
sawn
softwood
carriage
is
fixed
below
A
sawn
softwood
carriage
is
fixed
below
flights of a staircase to give support
under the centre of treads and also as a
fixing
for
plaster
on
the
soffit
or
fixing
for
plaster
on
the
soffit
or
underside of flights.

19. „
Shaped bottom steps:
For appearance sake the bottom
step of a flight of wood stairs is
shaped as either a quarter or a half circle.

20. „
Open riser wood stair: An open riser or ladder stair consists of strin
g
s with treads and no risers
so that there is a space between the treads.
Open riser wood stairs are constructed as straight flight stairs between
floors and there is no newel post to provide a fixin
g
for the handrail.

23. METAL STAIRS
„
T
heyareusuallyfabricatedfromsteeland
cast iron and their use is
g
enerall
y
gy
restrictedtofactories,godownsetc.Inits simplest
form
a
metal
stair
consists
of
simplest
form
,
a
metal
stair
consists
of
steel stringer to which steel angles are riveted
or
welded
and
metal
treads
are
riveted
or
welded
and
metal
treads
are
provided over them. Sometimes concrete isfilledinsteel
g
ratin
g
toformthetreads.

24. Th h
th
t
d
fi
it
th
„
Th
oug
h
th
eyares
t
rongan
d
fi
reres
is
t
ance,
th
ey
makesoundwhenusedbytheusers.
Th
l
d
f
il
ti
„
Th
eyarecommon
lyuse
d
f
orsp
ira
l
s
t
a
irs.
„
Properlyweldedironisoneofthematerialsused f
b ildi
ti
Wh
b ilt
ith
th
f
or
b
u
ildi
ng s
t
a
irways.
Wh
en
b
u
ilt
w
ith
th
ese
materials, stairways present light appearance
and
their
construction
is
carried
out
in
a
and
their
construction
is
carried
out
in
a
relativelyfastmanner,forwhichreasontheyare built
mainly
for
factories
workshops
built
mainly
for
factories
,
workshops
,
warehousesandemergencyexits.

25. „
Restin
g
places are usually made of non-
skid metal sheets or metallic
g
rates
g
allowing the passage of water and light. The
railings
of
these
stairways
are
also
The
railings
of
these
stairways
are
also
made of metallic grates allowing the passage
of
water
and
light
passage
of
water
and
light
.
„
T
he railin
g
s of these stairwa
y
sarealso
g
y
madeofmetallicmaterials.

33. T
hank Yo
u