The document provides information on formwork for concrete construction projects. It discusses health and safety considerations when working with concrete and formwork materials. It describes the importance of formwork for achieving a quality finished concrete surface. The document outlines design considerations and common materials used for formwork, including timber, plywood, steel, aluminum, plastics, and expanded metal and polystyrene. It provides guidance on properly erecting formwork, including ensuring proper support, bracing, and securing of all formwork components.

1. CONTENTS
Health awareness
The sign of a job well done
What’s needed for good formwork
Design
Materials
How to erect formwork
Using a release agent
Checks before concreting
Striking the formwork
Further reading
The downloadable booklets in the Concrete
on site series are a continuation of a series
originally issued in 1951 and have become
standard guides to site personnel.
3 Concrete
on site
!Safety on site
Many construction activities are
potentially dangerous so care is needed
at all times. Current legislation requires
all persons to consider the effects of
their actions, or lack of action, on the
health and safety of themselves and
others. Advice on safety legislation can
be obtained from any of the area offices
of the Health Safety Executive.
Concrete on site 3 - Formwork
OS003
© The Concrete Society
05/10
Formwork

2. Formwork
HEALTH Awareness
Dry cement powders in normal use
have no harmful effect on dry skin.
As with any dusty material there
may be ill effects from the inhala-
tion or ingestion of cement dust
and suitable precautions should be
taken.
When cement is mixed with water,
alkali is released. Precautions should
therefore be taken to prevent dry
cement entering the eyes, mouth or
nose, and to avoid skin contact with
wet concrete and mortar.
Repeated skin contact with wet
cement over a period of time may
cause irritant contact dermatitis.
The abrasiveness of the concrete or
mortar constituents can aggravate
the effect.
Some skins are sensitive to the small
amount of chromate that may be
present in cements and can develop
allergic contact dermatitis, but this
is rare.
Continued contact with the skin can
result in cement burns with ulceration.
Note that with alkali burns, pain is
not immediate.
Handling precautions
Protection for the eyes, mouth and
nose should be worn in circum-
stances when dry cement may
become airborne.
When working with wet concrete or
mortar, suitable protective clothing
should be worn, such as long-
sleeved shirts, full-length trousers,
waterproof gloves with cotton liners
and wellington boots. Clothing con-
taminated with wet cement, mortar
or concrete should be removed and
washed before further use. Should
concrete or mortar get into boots,
remove them IMMEDIATELY and
thoroughly wash the skin and the
inside of the boots before proceed-
ing with the job.
If cement enters the eye it should be
washed immediately and thorough-
ly with clean water and medical
advice sought.
Concrete or mortar elsewhere on
the skin should also be washed off
immediately.
Whenever there is persistent or
severe irritation or pain a doctor
should be consulted.
THE SIGN OF A JOBWELL DONE
There is an easy way to tell whether
a concreting project has been car-
ried out properly or not and that is
to check its appearance when the
job is finished. Good construction
will look attractive, whereas work
that has been carried out in a care-
less, slapdash manner will not.
Formwork is one of the two most
important factors that decide how
the concrete will look in the final
result (the other being the way the
concrete is placed and compacted).
This publication deals with the
formwork; for advice on placing and
compaction, refer to Concrete on
site 5: Placing and compacting.
Formwork is the mould for the wet
concrete. It shapes it, and holds it in
place until it has set and hardened.
Any defects in the formwork will
show on the as-struck concrete
!Formwork is made from many
materials including:
Timber
Aluminium
Plywood
Steel
Plastics
Polystyrene
Expanded metal sheet
Cardboard.
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3. Formwork
surface, so it is essential that all the
operations are carried out with great
care.
Formwork is made from expensive
materials and needs great skill in its
fabrication. Its importance can be
judged from the fact that fabricat-
ing, erecting and striking it often
cost more than the concrete it is
designed to shape and support.
Because of this, formwork usually
needs to be re-used over and over
again. This will be possible only if
it is handled, cleaned and stored
properly and responsibly.
A high standard of workmanship
is necessary to produce a high
standard of concrete work. Much
depends on the skill and expertise
of the workforce, although good
quality can be achieved in simple,
highly repetitive work with less
skilled labour.
There are specialised proprietary
formwork systems i.e. slip forms,
jump forms, and tunnel forms. These
are not covered in this booklet.
The concrete in the finished job will
provide a lasting commentary on
the skills of all those involved in the
construction.
WHAT’S NEEDED FOR GOOD
FORMWORK
As far as the operative on site is con-
cerned, there are four requirements
for good formwork:
1. It should be built to ensure
that the concrete is formed to the
required shape, size and position,
as well as providing the required
surface finish on the concrete.
2. The supporting system for the
formwork - the tie rods and align-
ment members of wall forms, or
the supports, lacing and bracing
of formwork for slabs - must be
installed in accordance with the
formwork drawing and the suppli-
er’s recommendations.
3. Formwork should be securely
fixed and all fixings needed for
erecting subsequent formwork
should be included.
4. It should be possible to strike
the formwork easily and safely and
without causing any damage to the
concrete.
Design
There are four main areas for form-
work; walls, columns, beams and
slabs. Formwork for the underside
of suspended slabs and beams
is known as soffit formwork. The
supporting structure of formwork is
known as falsework.
Wall formwork will be either double-
faced (in which tie rods keep the
two faces from spreading apart un-
der the pressure of the concrete) or
single-faced e.g. that for the edges
to small bases and pile caps.
Supporting single-faced formwork
calls for careful consideration and
for heights of 1m or more the form-
work should be specially designed
for the purpose.
Soffit formwork needs to be sup-
ported typically by steel or alumin-
Fig 1. Formwork construction

4. Formwork
ium vertical members. On smaller
contracts, adjustable metal props
are often used as falsework, but
proprietary deck support systems
are common for larger slabs. The
latter have replaced the traditional
tube-and-fitting supports, which
were labour intensive.
There are often many possible
solutions to the formwork problems
that could crop up on site. These
might involve the use of traditional
methods, or proprietary equipment-
sometimes a combination of both.
Wall formwork, for instance, is very
often made from plywood panels
supported by timber walings and
proprietary steel soldiers.
No matter what arrangement is
used, a drawing will be required.
This need not necessarily be a de-
sign drawing; a simple sketch will do
for small jobs. But it is vital that all
aspects of the problem have been
fully considered. This is especially
true for a large clear-span soffit
arrangement, or a cantilever section
of slab.
It is important to follow the arrange-
ment drawing as closely as possible,
because it will have been devised
by the formwork and falsework
designer to suit the job in hand, to
ensure that:
It is strong enough to take the
pressure or weight of the fresh
concrete during placing and com-
paction, as well as any other loads
it might have to face. Weak forms
will result in distortion, excessive
deflections, leaks or other failure.
These could mean that expensive
repairs to the hardened concrete
would be necessary.
It is easily and quickly erected
and struck, thus saving time and
money.
It is sufficiently stable in all
weathers.
It is easily and safely handled us-
ing available equipment- includ-
ing manhandling.
It provides suitable access for
handling, placing and compact-
ing the concrete.
It follows all the appropriate
safety regulations relating to
access, working areas, platforms,
toe boards and guardrails.
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It has joints between members
tight enough to prevent grout
leakage, honeycombing and
similar faults, which lead to a lack
of durability and can spoil the
appearance of the concrete in the
finished job.
Materials
A wide range of materials is used
for all parts of the formwork, from
backing members to the various
surface materials in contact with the
concrete.
Timber
Timber is the most common of the
various materials used for backing
members to the form face, because
it has the advantage of being easily
cut and assembled on site. It is used
as walings in wall forms and as bear-
ers in soffit forms.
Formwork made from timber is
known as‘traditional formwork’. This
is because the construction meth-
ods that are involved have been
used on sites for many years, and
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Fig 2. Traditional timber formwork,
walings (left) and bearers
Fig 3. Aluminium formwork is strong
and lightweight

5. Formwork
they are well understood by trained
operators.
Timber is graded by strength into
classes. It is important to use the
correct class of timber.
Aluminium
A range of proprietary beams and
smaller joists made from aluminium
may be used in formwork.
Aluminium is strong and light, and of-
ten you need fewer supports and ties.
The lighter sections will deflect
more than equivalent steel or timber
members, so always follow the
formwork design and the supplier’s
recommendations.
Plywood
Both traditional and proprietary
formwork use plywood for panels.
Ideally, the plywood should be
framed up in the largest-size panel
that can be handled on site. Ply-
wood often has a strong and a weak
way round, so make sure you always
follow the supplier’s recommenda-
tions on this point.
Take care not to damage the
faces and edges of the plywood,
especially when striking and during
storage
Seal cut edges and tie rod holes with
proprietary sealer or paint.
Steel
Steel is used in both proprietary and
purpose-made forms.
Proprietary systems usually consist
of panels with steel frames, clad
with either a plywood or steel fac-
ing. A range of adjustable props,
soldiers, light walings and a variety
of ties and accessories is available
for securing the formwork in place.
Purpose-made forms with steel
faces are often used when dimen-
sional tolerances are critical, or
when it is planned that the form will
be used over and over again. Such
re-use obviously results in great cost
saving, and it can be economical to
specify steel when it is intended that
the form will be re-used as little as,
say, a dozen times.
However, a steel form can be re-
used on many more occasions than
that - well over a hundred - provided
it is looked after and stored properly.
Plastics
Glass-reinforced plastics (grp) and
vacuum-formed plastics are used
when complicated concrete shapes
or surface features are to be cast
many times.
However, you need to consider very
carefully the type of release agent to
be used on plastics.
Vacuum-formed plastic will always
need support, but grp can be
fabricated with integral bearers
that make it unnecessary to provide
extra support for the face material.
Plastic formwork can be reused
many times, but you have to take
care when placing and vibrating the
concrete that you do not scour and
damage the face.
Proprietary waffle or trough form-
ers, used on voided slabs, can be
polypropylene.
Fig 4. Steel frames may be inlaid with
plywood or steel panels
Fig 5. Polypropylene and grp are
often used to form the voids in trough
and waffle floors

6. Formwork
Expanded Polystyrene
Expanded polystyrene can be sculp-
tured to give a single-use sheet form
liner. Its main advantage is the wide
variety of shapes to which it can be
formed. It is light and inexpensive,
but requires a support system to
withstand the concrete pressure.
When used on voided trough and
waffle slabs, it is coated with a
plastic sheet material to allow it to
be stripped cleanly.
Although expanded polystyrene is
used for forming openings and box-
outs, it can be used only once, and
is, therefore, wasteful. Also it can
leave a skin of plastic on the con-
crete surface. However, if you face it
with a rigid plastic sheeting, it can
be less expensive than framed-up
formers for openings and box-outs.
Expanded metal
Expanded metal can be used to
form inexpensive faces where the
finish is not important.
It is often used to form stop ends.
However, it is a material that cannot
be re-used, and does not necessarily
have to be removed.
Expanded metal’s main advantage
comes when it is used in tall struc-
tures, for here it reduces formwork
pressures.
Cardboard
Cardboard that has been coated
with a waterproof treatment is
sometimes used as formwork for
circular columns and for voids in
bridges and slabs.
Cardboard formers are generally
used only once. They need to be
well supported and braced to
prevent them from being distorted
and displaced by the concrete as it is
being placed and compacted.
Other
Formwork may be permanent,
remaining as part of the finished
structure for example steel concrete
composite decking. Form-face
materials may also have permeable
properties (controlled permeabil-
ity formwork) which improve the
surface characteristics.
Bolt-hole boxes
Bolt-hole boxes can be made from
many materials; timber, plywood,
expanded metal, expanded polysty-
rene or foamed polyurethane or be
obtained as ready-made proprietary
inserts.
Proprietary Formwork
A wide range of formwork panels,
soldiers, falsework and fast-track
systems is now available from vari-
ous suppliers.
Instruction manuals should be
supplied along with the equipment.
If you do not fully understand the
procedures, do not hesitate to ask
the supplier for advice.
It is most important to establish that
you are using the correct pieces of
equipment. Mixing items from differ-
ent suppliers can seriously affect the
structural strength of the completed
assembly, and must be avoided.
Fig 6. Expanded metal formwork
Fig 7. Proprietary formwork can save
time

7. Formwork
HOWTO ERECT FORMWORK
All construction projects are differ-
ent from one another, and have their
own particular problems. However,
this section covers the main points
you should watch in order to avoid
serious trouble when assembling
and erecting formwork.
Use all panels in their correct
positions. Paint numbers on them
so that you can see at a glance
which is which, and which way up
they go.
Make sure that props, shores,
walings, bearers, clamps and tie
rods are the right size and at the
correct spacing.
Check that the falsework is
securely braced, and is on a firm
foundation.
The correct washer plates should
be used with all ties, and set
square on frame members. This is
especially important with sloping
formwork. Do not overtighten
ties, for this might cause distor-
tion, and could result in failure of
the tie when it is fully loaded.
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Forms fastened to previously cast
concrete must be tightly fixed to
prevent grout loss. Cellular foam
plastic strips can be used to make
a seal. Or, for very high-qual-
ity visual concrete, you can first
gun a one-part, moisture curing,
synthetic rubber sealant on to the
old concrete.
Arrange the sequence of opera-
tions so that the formwork, and
any opening formers or box-outs,
provide a template from which
the reinforcing steel can be
properly spaced. This will ensure
that the correct concrete cover is
maintained in the finished work.
Any infill or closure panels, such
as those needed to make up non-
standard lengths, should marry
with the main formwork. Use a
fixing method that allows you
to fix and strip the infills without
causing damage. Avoid cutting, or
drilling holes in standard panels.
Holes that you have to make in
the formwork should be neat,
so that they can be patched or
plugged later on. Drill timber
from the face to avoid splintering.
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For high-quality work, the cut
edge of the hole should be sealed
in order to reduce water penetra-
tion.
Lightly tack all battens and block-
ing-out pieces so that they stay in
the concrete during the striking
of the formwork. Oil all boxes and
block-out formers before placing
any concrete, to ensure that they
can be easily removed after the
main forms have been struck.
Satisfy yourself before concreting
that all inserts and boxes are se-
curely fixed, and check that they
are slightly chamfered to make
them easy to remove.
Be certain you understand which
items are to be placed during
concreting, and how they are to
be fixed.
Pay particular attention to the
rigidity and line of stop ends and
joint formers, since these will be
seen on the face of the finished
work.
Remove all tie-wire clippings
and nails, which will stain both
the formwork and the concrete,
and get rid, too, of any dirt and
shavings.
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Fig 8. Check formwork is erected
correctly
Fig 9. Drill timber from the face

8. Formwork
Make sure that adequate access
and working platforms are in
place for concreting gang, and
that toe boards and guard rails
(including end rails) are provided.
Sloping or horizontal top forms
are subject to upward pressures,
and steps should be taken to stop
them from lifting.
The weight of large prefabricated
sections of formwork should be
marked on them so that you can
easily see what it is. Check that
the capacity of the crane at the
working radius is equal to lifting
them. Lifting points are usually
provided on the sections.
If necessary, a spreader or lifting
beam should be used to prevent
distortion. Make sure that inclined
slings are long enough. The flat-
ter they become, the less they
can lift. If you plan to lift by the
vertical soldiers, check that they
are adequately connected to the
walings.
When using proprietary systems,
make sure you understand the
manufacturer’s instructions. Any
special tools needed should be
obtained before work starts.
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Stop ends and day joints
Holes are often needed in stop ends
to ensure that projecting starter
bars for subsequent work are cor-
rectly positioned. Stop end forms
are easily made from expanded
metal, but if you use other materials
special care is needed to ensure that
the forms are grout-tight, and can
be withdrawn from the hardened
concrete- see Concrete on site No 7:
Construction joints.
Propping to soffit formwork
To support the soffit and prevent
excess deflect while it is gaining
strength, propping must be carried
out correctly. The props must be
in good condition and erected
properly, otherwise you risk having
a dangerous collapse.
The largest number of recorded
accidents involving formwork have
occurred because props, lacing,
bracing and ties were left out of the
falsework or taken away, often to
provide access, then not put back.
So, if it is necessary, make sure
that only the minimum number of
items is removed, that the details
are recorded and the parts always
replaced.
The load-carrying capacity of adjust-
able steel props is considerably
reduced if they are erected out of
plumb, and is further lessened if the
load is applied off-centre.
Bearers that are supported by props
should be no more than 25mm off
the centre of the prop head, and no
prop should be more than 1 in 40
out of plumb i.e. 25mm in 1m.
Check the props by using a 1m spirit
level to ensure that the end props
in each row are vertical, and eyeing
through the remainder. Check in
both directions.
A prop should not be used if it has
any of these defects:
a bend or crease in the tube
corrosion other than slight
rusting on the surface
a bent head or base plate
an incorrect or damaged pin.
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Fig 10. Working platforms must be
safe
Fig 11. Use the correct banksman’s
signals for the crane driver

9. Formwork
Above all, make sure that the
props have a firm bearing and that
they have sole plates. There are
several good guides to the safe use
of props. If in doubt, always seek
advice.
USING A RELEASE AGENT
The form-face in contact with the
concrete needs to be treated with a
release agent so that it can eventu-
ally be removed without adhering
to, and damaging, the surface finish
of the concrete.
Release agents are prepared by the
manufacturer to suit various require-
ments, and you must always follow
the instructions. Never dilute a
release agent, or mix different ones
together.
The agent is applied, before concret-
ing starts and before the reinforce-
ment is fixed, each time that the
form is used. The various materials,
such as timber, steel and grp, might
each require a different type of
release agent. Not all boards will
need a release agent so check the
manufactures product data sheets.
New timber and plywood are
absorbent, so it may be necessary to
apply a first coat of the appropriate
agent in advance, then a second
coat before they are used. Alterna-
tively, any absorbent surfaces may
be sealed with a suitable varnish,
barrier paint or wax. A single ap-
plication of release agent is all that is
necessary when the forms are then
used.
Care should be taken to apply the
correct amount of release agent.
The most common fault is to apply
too much. This can cause staining or
retardation of the concrete surface.
The right amount is a thin film ap-
plied uniformly by brush, roller or,
preferably, spray.
There is a simple check; touch the
surface of the formwork when you
have finished applying the agent;
it should seem only slightly greasy.
If you can feel or see that there is
excess, wipe it off with a clean rag.
Remember that the agents are
chemicals, and misuse can affect
your health. If it is not possible to
read the instructions on the con-
tainer because they have become
obliterated on site, see the COSHH
regulations to find out whether
any special precautions need to be
taken. Never use oil from a container
that is not clearly labeled, unless you
are sure it is a release agent.
CHECKS BEFORE CONCRETING
Sound formwork, properly erected
in accordance with the design
requirements, is an essential prereq-
uisite of a successful casting. It is im-
portant that the supervisor should
make a careful and thorough safety
and accuracy inspection of the form-
work before concreting starts.
This inspection should provide,
where applicable, satisfactory an-
swers to the following questions:
Is the formwork erected in ac-
cordance with the approved
drawings?
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!Common types of release agent:
Neat oils with surfactants. Used
mainly on steel faces, but also suit-
able for timber and plywood.
Mould cream emulsions. Good
general-purpose release agents for
use on timber and plywood.
Chemical release agents. Recom-
mended for high-quality work,
applied by spray to all types of form
face.
VERA’s - vegetable, oil-based release
agents are more environmentally
friendly, being biodegradable water
based products.
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10. 10
Formwork
Is the formwork restrained against
movement in all directions?
Is it correctly aligned and lev-
elled?
Are all the props plumb, and at
the right spacing?
Are bolts and wedges secure
against any possible loosening?
Has the correct number of ties
been used? Are they all in the
right places, and properly tight-
ened?
Are the proprietary items compat-
ible? Make sure that different
components do not get mixed up
Are all the inserts and cast-in
fixings in the right position, and
secure? Check that void formers
are firmly fixed, or tied down, so
that they do not float up.
Can any further inserts or box-
outs be fixed during concreting if
required?
Have all the stop ends been prop-
erly secured?
Have all the joints been sealed to
stop grout loss - especially where
the formwork is against a kicker?
Can the formwork be struck with-
out damaging the concrete?
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Are the forms clean and free from
rubbish such as tie-wire cuttings
and odd bits of timber or metal?
Has a release agent been applied,
and is it the correct one?
Is the reinforcement correct? Are
there enough spacers, and is the
depth of cover correct?
Are all projecting bars straight
and correctly positioned?
Is there proper access for placing
the concrete and compacting it?
Have all the toe-boards and guard
rails been provided?
How will you know when to strike
the formwork?
Has the curing been organized?
Once the initial checks have been
carried out by the supervisor, the
work will normally be inspected by
the clerk of works, or resident engi-
neer, before concreting proceeds.
The inspection, combined with a
general check on the security and
tightness of the forms, can save ac-
cidents and injuries, even loss of life.
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Once concreting starts
The work of placing and vibrating
can cause displacement of the forms
as work proceeds, so an eye should
be kept open for anything untoward
happening.
Tell-tale devices and stringlines
should be fixed so that a continuous
check can be made on alignment
and plumb during the placing and
vibrating operations.
Grout loss is an indication that some
movement has occurred (or that the
joints were not fixed properly in the
first place).
Before a wall or column pour starts,
the permitted rate of rise (in metres
per hour) must be known because
the formwork will have been
designed to withstand a specific
concrete pressure. The permitted
rate of rise will be affected by the
concrete, its consistence, the type
of cement used and whether it
contains any plasticizers or retarders
and the temperature.
To keep the concrete pressures
acceptable on a cold day, you might
have to slow down the rate of rise.
Fig 12. Look out for signs of
movement especially with external
vibrators

11. 11
Formwork
If the design pressure is exceeded,
formwork will be overloaded, pos-
sibly with disastrous results.
Someone experienced in the con-
struction of formwork should always
be standing by when concrete is
being placed, to keep an eye open
for any faults that might develop,
to cope with any emergency and
to carry out any necessary remedial
work. A supply of suitable equip-
ment, such as spare props and bolts,
should be held on site.
Any spilt concrete or grout leak-
age should be cleaned from the
formwork as soon as concreting is
completed. This is more easily done
at this stage than when the forms
are being put away for storage. It
also makes striking easier.
Early cleaning is particularly impor-
tant with large formwork panels,
for concrete stuck to them will add
considerably to their weight.
A light coating of oil on the back of
any steel formwork at the start of
operations will make cleaning easier.
A couple of other points to watch
during concreting:
Where unsleeved tie bars are
being used, ease them slightly
before the concrete sets, and re-
move them as soon as it is safe to
do so. If the bar is left unmoved, it
will be difficult to avoid damage
to the form or the concrete dur-
ing striking.
If a non-spacing tie system is used
and you have timber spreaders
holding wall formwork apart, the
spreaders should be removed
as soon as the concrete reaches
their level.
STRIKINGTHE FORMWORK
Formwork can be struck once
the concrete has gained enough
strength to be self-supporting, and
to carry any other loads that may be
put on it. Always obtain approval
before striking; the job specification
will normally give guidance on this,
but it might be overcautious.
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Faster striking times might be
authorized by an engineer. The size
and shape of the member, the char-
acteristics of the concrete and the
weather will all affect the decision
on when to strike, e.g during cold
weather, concrete does not harden
so quickly and formwork will usually
need to be left in place longer.
Before you start to strike, make sure
that a place has been allocated for
cleaning the formwork, and carrying
out any necessary repairs.
Site personnel not involved in the
operation should be kept well clear
to avoid any possibility of their be-
ing involved in an accident.
Begin by loosening ties and clamps
gradually, a little at a time, to pre-
vent the last tie from binding.
As you remove bolts, ties and
screws, do not just throw them to
the ground in the hope that you will
find them later. Put them instead in
boxes. Simple plywood boxes fixed
to the back of the panels are a good
idea, for then the bolts and ties will
travel with the forms.
Fig 13. Systematic removal of the
forms
Fig 14. Take care not to damage the
concrete or formwork when striking

12. 12
Formwork
Should the forms not immediately
come away once the ties have been
removed, carefully prise them loose
with hardwood wedges. Do not use
nail bars, they invariably damage
both the concrete and the forms.
If the striking is carried out within 12
to 18 hours of placing, the concrete
will still be weak and thus easily
damaged. Care must be taken.
Leave blocking-out pieces in the
concrete as long as possible, since
they protect the edges. Also, they
eventually shrink, and then it is
easier to remove them.
Larger sections of formwork above
ground will be lowered by crane.
The craneage will be controlled by
the nominated banksman using the
correct code of signals to guide the
crane driver.
Take care that the sections do not
bump into scaffolding or other
projections, and so get damaged,
as they are lowered. Ensure too,
that they come to rest on a level
surface so that they are not twisted
or forced out of shape - a common
cause of damage to formwork on
site.
Projecting nails left in the formwork
cause untold injuries on construc-
tion sites, so check whether there
are any, and remove or hammer
them down.
The method and sequence for strik-
ing soffit formwork should always
be approved before you start - then
strictly adhered to. It is all too easy
to overload the floors of multi-storey
buildings under construction if the
agreed sequence is not followed.
The usual sequence is to begin by
easing the supports by one turn
on the prop, then start striking at
midspan, working towards the walls
or columns, which will progressively
take the load.
On a cantilever, start at the end and
work towards the supports. If you
have a tee-beam supporting slabs
on both sides, first release the slabs
as already described, then strike the
tee-beam, starting from the centre.
As soon as the formwork is struck,
there can be a rapid loss of moisture
from the concrete surface. To
make sure there is no reduction in
surface strength and minimise the
occurrence of a dusty surface, cur-
ing should start immediately - see
Concrete onsite No 6: Curing.
Cleaning
Cleaning the face of forms should
start as soon as they have been
struck. A stiff brush will rid timber
and uncoated plywood of dust and
grout. Stubborn bits can be cleaned
off with a timber or plastic scraper,
rather than a steel one.
On grp, other plastics and quality
film-faced plywood, a brush and wet
cloth are all that should be needed.
If the forms are not going to be used
for some time, lightly oil steel ones
to stop rust from forming and coat
timber and unsealed plywood with
a release agent for protection. At the
same time, any depressions, splits
or holes should be treated with a
suitable filler such as plastic wood,
applied slightly proud then sanded
smooth.
Fig 15. Concrete must be cured after
striking

13. 13
Formwork
Storage
Good storage is essential to ensure
that formwork can be used again.
A tidy storage area reduces the risk
of damage, loss and wastage (all of
which can be very expensive) and
makes it easier to find the compo-
nents when they are next required,
thus saving time and labour.
Put the forms into storage as soon
as the cleaning and oiling are
finished, unless they are wanted
for immediate re-use. If you leave
formwork lying around, it will only
be damaged, or used for some other
purpose. More damage happens to
formwork when it is not in use than
when it is being erected and struck.
So take great care.
Panels and plywood sheets are best
stored horizontally on a flat base
so that they lie without twisting.
Stack them face to face to protect
the faces.
Paint code numbers on them so
that you can readily identify them
when they are next needed. Loose
walings and soldiers should also be
numbered, and stored with their
respective panels.
Small components such as bolts,
ties, wedges and keys are, as already
mentioned, best stored in boxes.
Larger ones e.g. clamps and props-
should be stacked off the ground.
The whole of the formwork should
be covered with tarpaulins or
plastic sheets to protect it from the
weather, with a dead air space left to
ensure ventilation.
Finally, fire extinguishers should be
kept nearby. Check them regularly
to make sure they are always in
working order.
!USEFUL CONTACTS
British Precast Concrete Federation
www.britishprecast.org
BSI Quality Assurance
www.bsi-global.com
Cement Admixture Association
www.admixtures.org.uk
Cementitious Slag Makers Association
www.ukcsma.co.uk
Construction Plant Association
www.cpa.uk.net
Meteorological office
www.metoffice.gov.uk.
Mineral Products Association
www.mineralproducts.org
Quality Scheme for Ready Mixed Concrete
www.qsrmc.co.uk
Sprayed Concrete Association
www.sca.org.uk
The Concrete Centre
www.concretecentre.com
The Concrete Society
www.concrete.org.uk
UK Cares (reinforcement)
www.ukcares.co.uk
UK Quality Ash Association
www.ukqaa.org.uk

14. 14
Formwork
FURTHER READING
For information on Standards and other publications, refer to the Concrete
Book Shop, www.concretebookshop.com
British Standards
BS 1881: Testing Concrete.
Part 113: Method for making and curing no-fines test cubes.
Part 130: Methodfortemperature-matchedcuringofconcretespecimens.
BS 4449: Steel for the reinforcement of concrete. Weldable reinforcing steel. Bar,
coil and decoiled product. Specification.
BS 4482: Steel wire for the reinforcement of concrete products. Specification.
BS 4483: Steel fabric for the reinforcement of concrete. Specification.
BS 5975: Code of practice for temporary works procedures and the permissible
stress design of falsework.
BS 7542: Method of test for curing compounds for concrete.
BS 7973: Spacers and chairs for steel reinforcement and their specification.
BS 8443: Specification for establishing the suitability of special purpose concrete
admixtures.
BS 8500: Concrete – complementary British Standard to BS EN 206–1: 2000,
Part 1: Method of specification and guidance for the specifier.
Part 2: Specification for constituent materials and concrete.
BS 8666: Scheduling, dimensioning, bending and cutting of steel reinforcement
for concrete. Specification.
BS EN 206-1: Concrete.
Part 1: Specification, performance, production and conformity.
BS EN 12350: Testing fresh concrete.
Part 1: Sampling.
Part 2: Slump test .
Part 4: Degree of compactability.
Part 5: Flow table test.
Part 7: Air content. Pressure methods.
BS EN 12390: Testing hardened concrete.
Part 2: Making and curing specimens for strength tests.
Part 3: Compressive strength of test specimens.
BS EN 13670: Execution of concrete structures.
BS EN 13286-41 Unbound and hydraulically bound mixtures: Part 41: Test
method for determination of the compressive strength of hydraulically bound
mixtures.
BS EN 14227-1 Unbound and Hydraulically bound mixtures – Specifications
– Part 1 Cement bound granular mixtures.

15. 15
Formwork
Further reading continued.
Building Research Establishment
Design of normal concrete mixes, 2nd ed, 1997
Formwork for modern, efficient concrete construction, BR495, 2007
The Concrete Society
Technical Report 52, Plain formed concrete finishes, 1999
Technical Report 62, Self-compacting concrete, 2005
Formwork – a guide to good practice, 2nd edition, 1995
Good Concrete Guide 2: Pumping concrete, 2005
Good Concrete Guide 6: Slipforming of vertical structures, 2008
Good Concrete Guide 7: Foamed concrete, application and specification, 2009
Good Concrete Guide 8: Concrete practice, Guidance on the practical aspects of
concreting, 2008
Checklist for erecting and dismantling falsework, 1999
Checklist for assembly, use and striking of formwork, 2003
Concrete Advice no 16, Assessing as struck in situ concrete surfaces, 2003
Concrete Advice no 20, Curing concrete, 2005
Concrete Advice no 30, Identity testing for strength in accordance with
BS EN 206-1 and BS 8500-1, 2007
Concrete Advice no 31, Identity testing of fresh concrete for properties other
than strength, 2007
Concrete Advice no 37, Mould release agents, 2008
Construction Industry Research and Information Association (CIRIA)
Concrete pressure on formwork, Report 108, 1985
Formwork striking times – criteria, prediction and methods of assessment,
Report 136, 1995
Action in the case of non-conformity of concrete structures, Report C519, 1999
Construct
Guide to flat slab formwork and falsework, 2003
A guide to the safe transportation of formwork and falsework equipment, 2005
A guide to the safe use of formwork and falsework, 2008
Health and Safety Executive (HSE)
Hand-vibration – The control of vibration at work regulations, 2005
The work at height regulations, 2005
The Control of Substances Hazardous to Health Regulations, 2002
Management of Health and Safety at Work Regulations, 1999
Managing Health and Safety in Construction, 2007
The Personal Protective Equipment at Work Regulations, 1992
The Manual Handling Operations Regulations, 1992
Highways Agency, Her Majesty’s Stationary Office (HMSO)
Manual of contract documents for highway works, vol 1, Specification for High-
way Works

16. 16
Other titles in the Concreteonsiteseries
Published by The Concrete Society
OS003
Published May 2010
© The Concrete Society
The Concrete Society
Riverside House, 4 Meadows Business Park
Station Approach, Blackwater, Camberley
Surrey GU17 9AB
Tel: +44(0)1276 607140 FAX: +44(0)1276 607140
www.concrete.org.uk
Other publications in this series are available from the
Concrete Bookshop at www.concretebookshop.com
Tel: +44(0)7004 607777
Formwork
1. Ready-mixed concrete
2. Reinforcement
3. Formwork
4. Moving fresh concrete
5. Placing and compacting
6. Curing
7. Construction joints
8. Making-good and finishing
9. Sampling testing fresh concrete
10. Making test cubes
11.Winter working