TIMBER STAIRS - METAL STAIRS

1. TIMBER STAIRS
A staircase with treads and risers constructed
from timber boardsfrom timber boards.
Timber stairs are comparatively light in weight
and easy to constructand easy to construct.
The timber used for the construction should be
free from fungal decay and insect attack andfree from fungal decay and insect attack, and
should be well treated before use.
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
thickness of about 45 mm may be used which is
sufficiently fire-proof.y p

2. COMPONENTS
The members of the
staircase flight are strings,g g ,
treads and risers.
The strings are the supportg pp
for the stairs and act as
inclined beam spanning
between the floor and the
landinglanding.
The treads and risers are
joined to form the steps ofjoined to form the steps of
the flight and are housed in
or fixed to strings whose
purpose is to support them.p p pp
For additional support, a bearer or a carriage may be placed
under the treads (In normal practice, one bearer is provided for aunder 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. Timber Stairs
The members of the flight are usually cut from theg y
timbers of the following sizes:
Treads 32 or 38, Risers 19 or 25, Strings 38 or 44.

4. Timber steps:
The thickness of timber step
(tread) should not be less
than 32 mm and that of riserthan 32 mm and that of riser
25 mm.
Timber tread and riser can be
simply joined by tongue andsimply 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 giveprovided 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. Joining risers to treads:
The usual method of joining
risers to treads is to cut tongues
on the edges of the risers and fitg
them to grooves cut 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 treadout of the groove in the tread
and the staircase ‘creaks’. To
prevent this it is a common
practice to secure the treads top
the risers with screws.
Nosing on treads: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 haveAfter the treads and risers have
been put together and glued
and wedged into their housingsand 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 stringand string.
Angle blo k e t i ng lAngle blocks are triangular
sections of softwood.
Their purpose is to strengthen
the right-angled joints betweenthe right angled joints between
treads, risers and strings.

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 suchwhich 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 post. For wider stairs the winders arep
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 immediately over it.y

10. Landings:
A landing is constructed ofA landing is constructed of
tongued and grooved
boarding on timber joists
which are supported on walls.
h f h lfIn the case of half space
landing, a timber joist is
placed in the wall at one end
and housed with the newel atand housed with the newel at
the other end.
Half turn landing:
A half turn landing isA half turn landing is
constructed with a sawn
softwood trimmer which
supports sawn softwood
l di j i t b dlanding joists or bearers and
floor boards.
Newel posts:
Th l t t fThe newel posts are cut from
100 X 100 timbers and
notched and bolted to the
timbertimber.

12. StringersSt ge s
Stringers are employed to provide support for the steps.
Strings are inclined wooden members 32 to 50 mm thickStrings are inclined wooden members 32 to 50 mm thick
and 25 to 38 cm deep. They are supported on newels,
trimming joists or pitching pieces.g j p g p
The thickness of strings may be 3to5 cm and depth may
b b 2 0be between 25 to 40 cm.
St i b f f tStringers may be of four types:
– Cut string
Housed string– Housed string
– Rough string
– Wreathed stringWreathed string

13. 1) Cut String:) 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-string, but it has the disadvantage of weakening
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 theparallel 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, glued and
wedged to the stringer.

15. Cut String Housed or closed stringg Housed or closed string
3) Rough String:
R h t i i t d d i id t i f th fRough stringers are introduced in wider stairs for the purpose of
rendering intermediate support to the steps.
4) Wreathed string:
It is curved or geometrical stair string It may be of cut or closedIt is curved or geometrical stair string. It may be of cut or closed
type.

17. Open Balustrade:
Traditional balustrade consists of
newel post, handrail and timberp ,
balusters.
Handrail
the top of the handrail is usuallyp y
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 stairshouse and 900 for all other stairs.
Balusters
they may be 25 or 19 square or
moulded They are either tenonedmoulded. They are either tenoned
or housed in the underside of the
handrail and tenoned in to the top
of closed strings or set intoo c osed s gs o se 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 timberclose string can be enclosed with timber
panels, plywood, hardboard, glass or
any sheet material fixed to a light
framework.
Spandrel:
the triangular space between the
underside of the lower flight of a stairunderside of the lower flight of a stair
and the floor is the spandrel.
Carriage:
A sawn softwood carriage is fixed belowA 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 orfixing 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 strings 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 fixing for the handrail.

23. METAL STAIRS
They are usually fabricated from steel and
cast iron and their use is generallyg y
restricted to factories, godowns etc. In its
simplest form a metal stair consists ofsimplest form, a metal stair consists of
steel stringer to which steel angles are
riveted or welded and metal treads areriveted or welded and metal treads are
provided over them. Sometimes concrete
is filled in steel grating to form the treads.

24. Th h th t d fi i t thThough they are strong and fire resistance, they
make sound when used by the users.
Th l d f i l t iThey are commonly used for spiral stairs.
Properly welded iron is one of the materials used
f b ildi t i Wh b ilt ith thfor building stairways. When built with these
materials, stairways present light appearance
and their construction is carried out in aand their construction is carried out in a
relatively fast manner, for which reason they are
built mainly for factories workshopsbuilt mainly for factories, workshops,
warehouses and emergency exits.

25. Resting places are usually made of non-
skid metal sheets or metallic gratesg
allowing the passage of water and light.
The railings of these stairways are alsoThe railings of these stairways are also
made of metallic grates allowing the
passage of water and lightpassage of water and light.
The railings of these stairways are alsog y
made of metallic materials.

33. Thank You