Form Work

FORM WORK
By K.Shah
B.E.(Civil Engg) NIT Rourkela,India
M.Sc. (Environment), University of
Leeds,UK
Ex-GM(Civil & Environment) – MNC
Currently Guest faculty-College of
Technology & Engineering

“ Form work or shuttering is a temporary
construction used as a mould for
structure, in which concrete is placed &
in which it hardens and matures”.

 Construction of form work requires lot of time &
material.
 Cost of form work is 20-25 % of cost of building.
 When required strength of concrete is achieved, form
work is removed.
 operation of removal of form work is called ‘stripping’
• Removed component of form work is reused for
another construction.
• Such forms whose components are used many times
are called ‘Panel Forms’.
• Forms made for non standard structures which can not
be used again is called ‘Stationary Forms’.

Classification of formwork
1. Wooden
2. Plywood
3. Steel
4. Combined (wood & steel)

Wooden form work
 Most common form work
 Disadvantage : Possibility of warping, swelling,
shrinkage.
 Water impermeable coating on wood form work
is applied to reduce warping, swelling,
shrinking
 With impermeable coating shuttering can be
removed easily.

Steel form work
Steel shuttering is used for major work.
Advantages:
a) It can be put to use for high number of times.
b) It provides ease of stripping
c) It gives smooth & even concrete surface
d) It posses high rigidity
e) It is not liable to shrinkage or distortion
f) It is costly.

Requirements of form work
A good form work should satisfy following
requirements:
a) Material of formwork should be cheap & can be reused many time.
b) It should be water proof & should not absorb water from concrete.
Shrinkage & swelling should be minimum.
c) It should be strong enough to take all loads coming on it (dead load of
concrete,live load of labour during pouring, compaction & curing.
d) It should be stiff enough so that deflection is minimum.
e) It should be light as far as possible
f) Surface of form work should be smooth for easy stripping
g) All joints of form work should be stiff so that lateral deformation under
load is minimum. Joints should be leak proof.

Indian Standard of Form work
(IS :456-1964)
(1) General :
The form work :
 shall conform to the shape, lines & dimensions as shown on
the plans.
 Shall be rigid during placing & compacting of concrete.
 Water tight to prevent loss of water from concrete.
(2) Cleaning & treatment of forms
 All rubbish, chippings, saw dust shall be removed from the
interior of form work before placing of concrete.
 Shall be wetted.

(IS :456-1964)
(3) STRIPPING TIME
Form work should not removed until good strength has come.
Type of form work Time
Vertical wall, columns 16-24 hrs
Soffit of slab (Prop should be refixed immediately) 3 days
Soffit of beam (Prop should be refixed immediately) 7 days
Props to slab Span < 4.5 m 7 days
Props to slab Span > 4.5 m 14 days
Props of beam (Span < 6 m) 14 days
Props of beam (Span > 6 m) 21 days

(IS :456-1964)
(4) Procedure when removing form work
 All form work shall be removed without shock or vibration as it
will damage the concrete.
 Before the soffit (bottom surface ) & struts (pole) are removed, the
concrete shall be exposed, to check that the concrete has
sufficiently hardened.
 Proper precautions shall be taken to allow for decrease in the rate of
hardening in cold water.
(5) Camber
 It is desirable to give form an upward camber (slope) to ensure that
beams do not sag when they have taken up their deflection.
 This should be done only when allowed in the design calculation of
the beam.

(IS :456-1964)
(6) Tolerances
Form work shall be so constructed that the internal
dimen sions are within the permissible tolerance
specified by the designer.

LOADS ON FORM WORK
The form work has to take following loads:
a) Live load due to labour
b) Weight of wet concrete
c) Hydrostatic pressure of the fluid concrete acting against the
vertical or inclined faces of form
d) Impact due to pouring of concrete.
 Live loads of labour & equipment including impact may be taken
as 370 Kg/m2.

LOADS ON FORM WORK
HYDROSTATIC PRESSURE:
Hydro static pressure due to fluid of
concrete depends on :
a) Quantity of water in concrete
b) Size of aggregate
c) Rate of pouring
d) Temperature

HYDROSTATIC PRESSURE:
Hydrostatic pressure is maximum during pouring
and decreases when concrete becomes hard.
Setting time may be taken as ¾ to 1 hour.
Only height of concrete poured in ¾ to 1 hour is
taken into account for calculation of hydrostatic
pressure on form work.
For 1.5 m height of concrete, equivalent weight
of concrete may be taken as 2300 kg/m3.

• HYDROSTATIC PRESSURE:
For higher height, the equivalent weight of
concrete is reduced.
When height of concrete in one pour is 6 m, the
equivalent fluid weight may be 1200 kg/m3.
For intermediate heights between 1.5 to 6 m
poured within the setting time of ¾ hour linear
interpolation of unit weight between 1200 to
2300 kg/m3 may be taken.

SHUTTERING FOR COLUMN
It consists of :
a. Sheeting all round the column periphery
b. Side yokes & end yokes
c. Wedges
d. Bolts with washers

SHUTTERING FOR COLUMN
 The side yokes & end yokes consists of 2
numbers each
 They are suitably spaced along the height of
column
 Two side yokes are comparatively of heavier
section & are connected together by 2 long
bolts.
 Four wedges one at each corner are inserted
between bolts & end yokes
 The sheathing is nailed to yokes.

SHUTTERING FOR BEAM & SLAB FLOOR
 The slab is continuous over number of beams.
 The slab is supported on 2.5 cm thick sheathing laid parallel to
main beam.
 The sheathing is supported on wooden battens which are laid
between the beams, at suitable spacing.
 In order to reduce deflection, the battens may be propped at
middle of the span through joists.
 The side forms of the beam consists 3 mm thick sheathing.
 The bottom sheathing of the beam form may be 5 to 7 cm thick.

SHUTTERING FOR BEAM & SLAB FLOOR
 The end of the battens are supported on ledger which
is fixed to cleats throughout the length.
 Cleats 10 cm x 2 cm x 3 cm are fixed to the forms at
the same spacing as that of battens, so that battens
may be fixed to them.
 The beam forms is supported on a head tree.
 The shore or post is connected to head tree through
cleats.
 At the bottom of shore, two wedges of hard wood are
provided over a sole piece.

SHUTTERING FOR STAIRS
• The sheathing or decking for deck slab is carried on
cross joists
• Cross joists are supported on raking ledgers.
• Ledger is 7.5 cm x 10 cm size.
• Cross joists are 5 cm x 10 cm size
• Riser planks are 4 -5 cm thick
• Planks are bevelled at bottom to permit the whole of the
tread faced to be trovelled.

SHUTTERING FOR STAIRS
• Riser plank are fixed after reinforcement has been fixed
in position.
• Outer end of of risers are carried by a cut string made of
5 cm plank.
• The cut string is strutted to the cross joists by 5 cm x 10
cm struts.
• The wall ends of the riser planks are carried by 5 cm x
10 cm hangers secured to 5 cm thick board fixed to wall.
• Treads are left open for concreting & vibration.
• Stiffner joists of 5 cm x 10 cm is placed along the middle
of the riser planks.
• Stiffner is wired to cross joists through decking.

FORM WORK FOR WALLS
a) The boarding is 4 to 5 cm thick for walls of 3 to 4 mt
height.
b) Boards are fixed to 5 cm x 10 cm posts known as
studs or soldiers
c) Studs are paced at spacing of 0.8 m.
d) Horizontal wallings of size 7.5 cm x 10 cm are fixed to
the at suitable interval.

MOVING WALL FORM
a) In moving wall forms, panels are made of 0.6 x 1.8 m size so that
handling & stripping is easy.
b) 15 mm ply board is used instead of boarding
c) The panels are installed in such a way that the lower panel can
be removed when concrete is hard and used higher up wall.
d) Framing of size 5 cm x 10 cm is used to ply shutter.
e) The panels are fixed to a central and two end studs.
f) Each stud consists of two pieces of timbers, 5 cm x 15 cm apart.
g) The end strut of each panel secures adjucent panel.
h) Boards are reversed for 1st lift ; for succeeding lifts, bolts pass
through holes formed to previous lift.
i) For rapid construction of a constant thickness wall, continuously
rising form, commonly known as sliding shutter is used

Form Work

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to Form Work

Similar to Form Work (20)

More from Kezar Ali. Shah

More from Kezar Ali. Shah (6)

Recently uploaded

Recently uploaded (20)

Form Work