Fabricating, installing and removing wooden formworks

WEB SCRIPT Construction
Sector:
Qualification: Carpentry NC II
Unit of Competency:
Module Title: Fabricate, Install and remove wooden formworks
Learning Outcomes:
Developer/s: Fabricating, Installing and removing wooden formworks

TITLE This module covers the knowledge, skills and attitudes to fabricate, install and remove
wooden formworks
OBJECTIVES Jeanelle A. Samson

INTRODUCTION Fabricating, Installing and removing wooden formworks
LESSON 1 At the end of this module you must be able to:
TOPIC 1
1. Prepare materials, tools and equipment
2. Lay-out and cut dimension of form sheating and stiffeners
3. Assemble and erect form panels and components
4. Erect wooden scaffolds
5. Strip form panels and dismantle scaffold
6. Clean and store reusable form panels and components

This includes Materials for fabricating formworks, Mechanical properties of
lumber and Economic use of materials
Prepare materials, tools and equipment

Materials for Fabricating Formworks

Formwork is a die or a mold including all supporting structures, used to shape and
support the concrete until it attains sufficient strength to carry its own weight. It should
be capable of carrying all imposed dead and live loads apart from its own weight.

Formwork is an ancillary construction, used as a mould for a structure. Into this
mould, fresh concrete is placed only to harden subsequently. The construction of
formwork takes time and involves expenditure up to 20 to 25% of the cost of the
structure or even more. Design of these temporary structures are made to economic
expenditure. The operation of removing the formwork is known as stripping. Stripped
formwork can be reused. Reusable forms are known as panel forms and non-usable are
called stationary forms.

A. Materials used for Formwork
Materials used for the construction of concrete formwork range from traditional
materials such as wood, steel, aluminum, and plywood to nontraditional materials such
as fiberglass. Wood products are the most widely used material for formwork.

1.Plywood are the material used most for formwork for the facing panel because it
is high in quantity whereby the material is easy to get. Besides that, plywood can be
handled better because it is easy to cut it and fix as a formwork. This includes the easy
handling of it.

2. Timber This is the most common material used for bracing members to the form
face. Like plywood, it can be easily cut to size on site. Formwork made from timber is
called traditional formwork. The construction methods using timer formwork have been
used on site for years, and all well understood by trained operators.

3. Metal Panel Metal formwork has a very
high reuse potential. So, it is more economical
than timber where repetitive work is necessary.
Steel forms become cost-efficient after about a
dozen uses, although they can be used up to 100
pours if they are carefully cleaned and stored.

4.Plastic (FRP) Another material used here is
the fiberglass-reinforced plastic as a formwork. Its
functions well because of its properties such as
Mold ability, Light weight, Strength and
Toughness.

B. Construction of Forms consist of:

1. Plywood- It is made in thickness of ¼, 3/8, ½, 5/8, and ¾ inch, and in widths up to
48 inches. The 8-foot lengths are most commonly used. The 6/8- and ¾-inch thickness
are most economical.

2. Supporters or studs- Vertical studs make the sheathing rigid. These studs are
generally made from 2x4 lumber. Studs also require reinforcing when they extend more
than 4 feet.

3. Braces- Braces give the forms stability. The most common brace uses a horizontal
member and a diagonal member nailed to a stake and to the stud or wale.

4. Spacer- Spreaders must be placed near each tie wire. Spreaders are cut to the
same length as the thickness of the wall and placed between the two sheathing surfaces
of the forms.

5. Tie wire- Tie wires hold the forms secure against the lateral pressures of
unhardened concrete. Double strands are always used. Ties keep wall forms together as

the concrete is positioned. The tie wire is made taut by twisting it with a smooth metal
rod or a spike.

6. Assorted CWN- refers to the different size of nail ranging from 1”-4” (25mm-
100mm) in length.

C. Formwork detail for different structural members
In concrete construction formwork is commonly provided for the following
structural members.

1. Formwork for sloping side column
It consists of:
• Side Support
• Side Planks
• Cleats

2. Wall foundations
It consists of:
• Plywood Sheeting
• Struts

3. Formwork for Wall

It consists of:

• Timber Sheeting

• Vertical Posts

• Horizontal

members

• Rackers

• Stakes

• Wedges

After completing one

side of formwork

reinforcement is

provided at the place

then the second side

formwork is

provided.

4. Formwork for Column
It consists of:
• Side & End Planks
• Yoke
• Nuts and Bolts
Two end & two side planks
are joined by the yokes and
bolts.

5. Formwork for Slabs & beams
It consists of:

• Sole plates
• Wedges
• Props
• Head tree
• Planks
• Batten
• Ledgers
- Beam formwork rests on head tree
- Slabs form work rests on battens and joists
- If prop height are more than 8’ provided horizontal braces

6. Formwork for Stairs
It consists of:
• Vertical and inclined posts
• Inclined members
• Wooden Planks or sheeting
• Stringer
• Riser Planks

TOPIC 2 Mechanical Properties of lumber

Basic understanding of mechanical properties of lumber is necessary for

concrete formwork design. Wood is different from any other structural material

in that allowable stresses of wood are different according to the orientation of

the wood.

A. Bending Stresses

The figure below

shows a simply supported

wood beam with a

concentrated load applied

at the midpoint. This

process results in bending.

The Lumber is stressed

internally to resist the

external loads. Bending in a

member causes tension

forces in the extreme fibers

along the side closest to the

applied load. The maximum

stress induced in the fibers

which occurs at the edges,

is referred to as the

“extreme fiber stress in

bending”. This stress is

highly dependent on the

parallel-to-grain strength of

the wood in both tension

and compression.

B. Modulus of Elasticity (MOE)

Modulus of

elasticity is a measure of

stiffness. This factor (MOE) is a relationship between the amount of

deflection in the member and the value of load applied that causes the

deflection. The amount of deflection depends on the size of the

member, the span between the supports, the load, and the particular

TOPIC 3 member specie of wood. The parallel-to-grain MOE (i.e., the stiffness
when wood is pushed or pulled parallel to the wood grain) is about 30
times greater than the perpendicular-to-grain MOE.
C. Tensile and Compressive Strengths

Tensile strength is a measure of the ability of wood to resist
pulling forces. On the other hand, compressive strength is a measure of
the ability of wood to resist pushing forces. For clear wood (wood
without defects), the tensile and compressive strengths for parallel-to-
grain loads are approximately 10 times greater than for loads applied
perpendicular to the wood grain.

Economic use of materials

Timber is an economical material of formworks construction but it has a short
life span. As the reusability of timber formwork is low and it can only be reused 8-15
times, several sets of timber formworks are needed for a high-rise building or a large
project. Hence, the cost of the formwork is high in long run.

Timber for formwork should satisfy the following requirement:
It should be
• well-seasoned
• light in weight
• easily workable with nails without splitting
• free from loose knots

Plywood Resin bonded plywood sheets are attached to timber frames to make
up panels of required sizes. The cost of plywood formwork compares favorably with that
of timber shuttering and it may even prove cheaper in certain cases in view of the
following considerations:

• It is possible to have smooth finish in which case on cost in surface
finishing is there.

• By use of large size panels it is possible to effect saving in the labor cost
of fixing and dismantling.

• Number of reuses are more as compared with timber shuttering. For
estimation purpose, number of reuses can be taken as 20 to 25.

Steel formworks might have the high cost at the beginning of the construction
but as steel formwork has a long lifespan and high reusability; it can save the cost in long
run. This is because less replacement of old formwork is needed. It can save concrete
volume needed because it can form a long span comparing to timber formwork.

This consist of panels fabricated out of thin steel plates stiffened along the edges
by small steel angles. The panel units can be held together through the use of suitable
clamps or bolts and nuts. The panels can be fabricated in large number in any desired
modular shape or size. Steel forms are largely used in large projects or in situation where
large number reuses of the shuttering is possible. This type of shuttering is considered
most suitable for circular or curved structures.

Steel forms compared with timber formwork:
• Steel forms are stronger, durable and have longer life than timber
formwork and their reuses are more in number.
• Steel forms can be installed and dismantled with greater ease and
speed.
• The quality of exposed concrete surface by using steel forms is good and
such surfaces need no further treatment.
• Steel formwork does not absorb moisture from concrete.
• Steel formwork does not shrink or warp.

A. Tips for avoiding waste construction materials
1. Study carefully the plan and detailed drawing.
2. From the given detailed drawing, you can study its different parts, including

sizes of these parts.
3. Cutting lumbers, always refer to the schedule of cutting.
4. Always determine the methods of measurement used in the plan for marking.
5. Always remember the principles for cutting “measure twice and cut once”

LESSON 2 6. In cutting lumber and plywood, always use effective tools.
TOPIC 1
Lay-out and cut dimension of form sheating and stiffeners

Form design

Form is a temporary boarding, sheathing or pan used to produce the desired
shape and size of concrete. The structural members of a building are built-up into its
desired shape and dimension through the use of forms which serve as mold for the
mixed concrete.

Concrete mixture is generally semi-fluid that produces the shape of anything
into which it is poured. Concrete form should be water tight, strong enough and rigid to
sustain the weight of the concrete. It should be simple and economically without
damaged to themselves or to the concrete.

A. Form Design
1. Importance of Formwork
• Protects the concrete
• Aids in the curing of the concrete
• Support any reinforcing bars or conduit embedded within it.
• Represents up to one-third of a concrete structure’s total cost
2. Factors influencing form design
• Nature of the structure
• Availability of equipment and form materials
• Anticipated reuse of the forms
• Familiarity with construction methods that influence the formwork
design
• Strength of the forming materials and the loads they must support
• Concrete’s final shape, dimensions, and surface finish.

B. Form Characteristics
1. Ensure that the forms are tight, rigid, and strong. Loose forms permit loss of
cement which can result in-

• Honeycombing. Honeycombing is when the concrete is not
satisfactorily consolidated or vibrated air pockets form within the

concrete and present a pocked appearance.

• Sand streaking. Sand streaking occurs when concrete loses too
much water due to loosen forms; the water carries sand with it
through the gaps in the formwork and causes streaking.

Topic 2 2. Ensure that the forms are braced enough to align them and strong enough
to hold the concrete.

3. Take special care in bracing and tying down forms used for configurations,
such as retaining walls. Ensure that the forms are wide at the bottom and
taper toward the top.

4. Ensure that wall forms are braced properly. The concrete in wall forms, such
as the first pour, tends to lift the form above its proper elevation.

5. Reuse forms by constructing them in a manner that allows easy removal and
replacement with minimal damage.

Prefabrication of formwork panels

Prefabricated formwork panels are indispensable for beam and column formworks.
Prefabricated formwork panels, however, are also recommended for series production
of foundation and ceiling formworks.

In that case the construction of the panels differs from that of panels for beam and
column formworks, but the technology of prefabrication is the same.

A good formwork should satisfy the following requirements.
• It should be strong enough to withstand all types of dead and live loads
• It should be rigidly constructed and efficiently propped and braced both horizontally
and vertically, so as to retain its shape
• The joints in the formwork should be tight against leakage of cement grout.
• Construction formwork should permit removal removal of various parts in desired
sequences without damage to the concrete.
• The materials of the formwork should be cheap, easily available and should be
suitable for reuse.
• The formwork should be set accurately to the desired line and levels should have
plane surface.
• It should be as light as possible.
• The material of the formwork should not warp or get distorted when exposed to the
element.

LESSON 3 • It should rest on firm base.
Topic 1
A. Hand tools and machines
• Circular saw
•Hand saw
•Hammer
•Wrecking bar
•Folding rule
•Try square
•Measuring rods

Beams and column
You must enter all sizes required from the working drawing. Derive the sizes

from the dimensions of the column for which the formwork is to be made. Prepare the
size distribution of the stiffeners. Then Cut up the boards. Locate the sizes of the forms
to the plywood at both ends then using your chalk line, mark the boundaries to be cut.
Do not place the rough edge of the board to the inside of the formwork. Always
consider the economy use of materials. After that cut the stiffeners straps to length.
Use 2”x2” lumber for the stiffeners. Butt joint is commonly used in this construction.
Adopt the schedule for cutting. After cutting, arrange and classify cut members ready
for assembling. Remember if you use circular saw for cutting plywood ask the
Permission of your teacher

Assemble and erect form panels and components

Assembling form panels and stiffeners

Constructs built-in-place or prefabricated wooden forms, according to
specifications, for molding concrete structures: Studies blueprints and diagrams to
determine type and dimension of forms to be constructed. Saws lumber to blueprint
dimensions, using handsaw or power saw, and nails lumber together to make form
panels. Erects built-in-place forms or assembles and installs prefabricated forms on
construction site according to blueprint specifications, using hand tools, plumb rule, and
level. Inserts spreaders and tie rods between opposite faces of form to maintain
specified dimensions. Anchors and braces forms to fixed objects, using nails, bolts,
anchor rods, steel cables, planks, and timbers.

One of the oldest tricks in the woodworking book, so to speak, is a simple method
for determining when any assembly or item is square. This basic trick really isn't a trick
at all; it is based on Pythagorean's Theorem, which states "the sum of the squares of
two sides of a right triangle is equal to the square of the third side, or hypotenuse."
Now, while you can always use the 3-4-5 Rule to determine square on any scale when
we are laying out a project, there is a more precise way to determine whether your
nearly- completed assembly is square.

Measure the diagonals with a tape measure and check to see if the two
distances match. If they are equal, your assembly is square.

Case in point: take a look at the drawing of a raised-panel exterior door on this page. If
we measure from one corner to the opposite corner diagonally (as shown by the red
line), and then compare that distance to the opposite diagonal measurement (as
depicted by the blue line), the two distances should match exactly. If they are equal, the
assembly is square.

Now, what do you do if the two diagonal measurements don't match? Adjust
the assembly. In the image above, if the red line's length is longer than the blue line's
length, push inward on the two red corners. If the blue line's length is longer, push
inward on the two corners of the assembly at the ends the blue line. After adjusting,
cross-measure both diagonals to check for square again. Keep adjusting and cross-
measuring both diagonals until the distances match, and your assembly will be square.

It goes without saying (that's why I'm going to say it) that the item you're
measuring should be designed to have four right-angle (90-degree) corners. In other
words, if the two long sides or the two short sides of the assembly aren't equal in length,
this rule cannot be applied properly. However, any parallelogram can be squared by
making the a forementioned measurements and adjustments.
Finding Square Using the 3-4-5 Rule

Understand the 3-4-5 method. If a triangle has sides measuring 3, 4, and 5 feet
(or any other unit), it must be a right triangle with a 90º angle between the short sides.
If you can "find" this triangle in your corner, you know the corner is square. This is based
on the Pythagorean Theorem from geometry: A2 + B2 = C2 for a right triangle. C is the
longest side (hypotenuse) and A and B are the two shorter "legs."

Methods for Squaring-up Stock
Some woodworking plans call for lengthy pieces of stock with four square edges.

Let's assume, for a moment, that your current woodworking project requires four 36-
inch table legs made out of two-inch square stock. You glue up three pieces of 3/4-inch
thick material, but three sides will need to be trimmed in order to obtain the 2x2 finished
size.

Temporary Fixing and/or Permanent Assembly Techniques
Metal-plate-connected wood roof trusses are common components in the

construction of light-framed building structures. They are most commonly used in short

span (<50') residential structures but are also used in long span (up to 80') commercial
applications. The precise manufacturing and pre-engineered aspects of wood trusses
allow for quick and easy erection upon their arrival on site. With this ease of assembly
comes a variety of important guidelines and instructions for the installer to follow. The
failure to follow or observe these guidelines has led to the collapse of many wood roof
truss systems. Truss failures are often attributed to improper or lack of temporary and
permanent bracing, incorrect loading or overloading during construction, high winds
during erection, and weak members or bad joint connections. Many of these problems
grow out of the difference between how trusses work and how the builders using them
understand them.

Opportunities for Failure

Storage, Handling, and Erection Errors
The improper handling of wood roof trusses prior to erection can create

opportunities for failure before the truss is even placed. Upon delivery, trusses should
be stored in a dry, flat location, close to the structure to limit movement from storage
to erection.

Temporary Bracing
Temporary bracing is required to hold wood trusses true to line and dimensions,

plumb, and in a stable condition until permanent truss bracing and other permanent
components necessary for the overall stability of the structure are completed.

Permanent Bracing
Permanent bracing is required after the erection of the trusses is complete.

Bracing such as the roof sheathing, fascia board, connection to the top plate, and ceiling
drywall all function as a form of permanent bracing along with their original intended
use. While this fully braces the entire perimeter or diaphragm of the truss, the internal
webs and members may require additional lateral bracing. This is typically accomplished
by installing long 2"x4" members to the internal webs as required by the truss engineer
and is shown on the truss profile shop drawings and represented by the cross section of
a 2"x4"on a member. Lateral bracing must lap at least two trusses at a bracing break (at
the ends of the 2"x4"s) to maintain continuity within the bracing. The most common
failure type for trusses missing permanent bracing is compression members buckling
due to lack of lateral stability
Overloading Daring Construction

This can occur when placing heavy concentrated loads on the trusses during
construction. Some possible sources of these loads are stacks of plywood/OSB for the
roof sheathing, gypsum wall board, roof gravel or ballast, HVAC equipment, and roofing
shingles. No construction load should ever be placed on trusses without proper bracing
and when placed, they should be broken down into smaller units and placed over panel
points or main supporting members.

Material Failures
Wood is a natural material which has inherent flaws and weaknesses. Typical wood

truss construction uses #2 grade lumber or better for the top and bottom chords as well
as the internal webs. Wood's strength is reduced by high moisture content and
increased temperature, often seen in the attic space of a structure. Truss engineers
account for this in their design butt here are circumstances beyond this which are not
typically considered. Exposure to prolonged wetting from rain during construction can
reduce the load carrying capacity at the connection by 40%. After drying, the joint

LESSON 4 connections still have a strength loss of about 10% and it' stiffness loss can range from
TOPIC 1 12%-37%

A. Assembling Form Panels using Forming Boards
1. Prepare the work. Make available the tools and materials. A work table is
to be manufactured
2. Enter all sizes required into the working drawing. Derive the sizes from the
dimensions of the beam for which the formwork is to be made. Prepare the
size distribution of the cover straps in particular.
3. Cut up the boards. The board width should not be exceeded 140 mm. Do
not place the rough edge of the board to the inside of the formwork.
4. Cut the stiffening cover straps to length. Cover straps to have a width of
approx. 55 mm with 25 mm projection for comer joints.
5. Put the cover straps on the arranged boards according to the size
distribution made. Use measuring rod, if necessary.
6. Nail the cover straps on the board-panel. It is provisional nailing with short
nails (40mm). Use as many nails as necessary to make the panel stable in
itself.
7. Nail the cover straps on the boards from the opposite side. Turn over the
provisionally nailed board-panel and nail it with 70 mm long nails. Two nails
per board are to be diagonally arranged at the cover strap joint.
8. Clinch the nail tips. Turn over the panel again and clinch the penetrated nail
tips.

Erect wooden scaffolds

Scaffolds safety rules

These safety rules cover generalized situations only and should not be used to replace
ant other additional safety and precautionary measures that may be necessary to cover
the many usual or unusual conditions encountered during installation or dismantling.

1. Follow safe practice of the safety rules and comply with OH&S laws and other
federal, state and local rules, codes and regulations pertaining to scaffolding
during any use of the equipment.

2. The potentially hazardous nature of scaffolding assembly makes it important
that all personnel assigned to this work be instructed in theses safety rules, safe
practices and procedures and be under the supervision of an experienced person.
Ensure that these Safety rules are posted and that all assemblers and users of the
scaffold are aware of and follow them.

3. Report any unsafe conditions to supervisors. Do not work or allow persons to
work on scaffolds when sick or suffering from dizziness, unsteadiness or any other
physical symptom which could affect their ability to work safe.

4. Inspect all equipment before use. Never use any equipment which is damaged,
defective, or deteriorated in any way.

5. Inspect assembled scaffold frequently and be sure that it is maintained in a safe
condition, ensure that the scaffold connection have not become loosened and
that components have not been improperly released or removed.

6. Maintain all equipment in good repair. Never use corroded or excessively rusted
equipment; the strength of such equipment is not known.

7. Consult your scaffolding supplier when in doubt. Never take chances.
8. Always read these safety rules in conjunction with all safety regulations.

LESSON 5 9. Always place scaffolds on a sound, stable surface and assure that it is adequate
TOPIC 1 to support the intended scaffold loads. Never place scaffolds on unstable where
loose objects could tip, break or become dislodged.

10. Lift and lower components carefully and safety. Use tag lines where appropriate
to the handling method. Never allow excessive quantities of components
consistent with the progress of the work. Lower dismantled components as soon
as possible. Never drop components deliberately.

11. The tieing of the scaffold to the structure is of great importance to the stability
and safety of the scaffold. Assure that the structure to which the scaffold is tied
or anchored is capable of safety supporting all loads imposed by the scaffold.

12. Free standing scaffolds other than wall scaffolds must be restrained from tipping
by guying or other means or otherwise stabilized as appropriate, recognizing that
stability is essential to the safety of the scaffold.

13. Install guardrails, mid-rails, and toe-boards at all openings, open sides, and ends
of every work platform.

14. Never use ladders or makeshift devices on tops of scaffold to increase the height.
Never place plank on or stand on guardrails and mid-rails.

15. Power lines near scaffolds are dangerous. Use extreme caution and consult the
electrical company to have the lines de-energized, insulated, or otherwise
rendered safe. Never allow any installation or use of scaffolds until this is
completed.

16. Proper care and precautions must be taken when using cantilevers to prevent
tripping of the scaffold

17. For mobile scaffolds following these additional safety rules
a) Never ride mobile scaffolds.
b) Remove all materials and equipment from the scaffold before moving.
c) Lock castor and outrigger brakes when scaffold is not being moved.

d) Do not attempt to move mobile scaffold without sufficient help and
roll on even surfaces only.
e) The maximum platform height of a mobile scaffold must not be
exceeded. All OH &S laws must comply when using mobile scaffold.
f) Move the scaffold using the bottom frame. Never attempt to move the
scaffold when on top.
g) If mobile scaffolds are used outdoors, care must be taken to assure
that they cannot become unstable due to wind or other conditions.
18. Do not overload scaffolds. Refer to and do not exceed the scaffold load
capacities.

Strip form panels and dismantle scaffold

Removing Formwork

Stripping is the operation of removing the forms. Formwork can either be partially
stripped by removing small areas to prevent the slab from deflecting or completely
stripped to allow the slab to deflect.
As a general rule, formwork supporting members should not be removed before the
strength of concrete has reached at least 70 percent of its design value.

A. Order and Method of Removing Formwork

1. Shuttering forming vertical faces of walls, beams & column sides should be
removed first. Shuttering forming sofit to slab should be removed next.

TOPIC 2 2. Shuttering forming soffit to beams, girders or other heavily loaded member
should be removed in the end.
LESSON 6 B. Striking
TOPIC 1 • The specification will normally give guidance on when forms can be struck and
these times may be governed by the size and shape of the member, the concrete
mix, and the weather.
• To strike the wall form, ties and clamps should be loosened gradually, a little at
a time.
• To remove the props, release the props evenly in small stages starting at the
middle of the span and working out towards the supports. This can avoid
overloading of the props at the center of the span due to large deflection at the
center.
• Always withdraw or hammer down projecting nails as the formwork is struck
from the concrete.
• Make sure that other trades are kept away from areas below those where
striking is being done.

Maintenance and Storage of Formwork

Provision must be made for the removal and storage large sections of formwork.
A level storage area is required to store formwork after striking.
They should be well cleaned before storing because the grout remaining on the forms
will become hard and stubborn making it difficult to reuse. Metal panels need a light
coating of oil before storage to prevent rust. All forms need to be carefully stacked and
stored. Panels of forms should be kept horizontal and face to face. The forms and
components should be clearly marked and kept together for easy identification on
reuse. A tidy store reduces wastage, damage and losses.

Cleaning
• As soon as the formwork has been struck, it should be cleaned, not left until it
is wanted again.
• Timber and plywood forms should be cleaned with a stiff brush to
remove any grout; a timber scraper should be used for stubborn bits of grout.
• With glass reinforced plastics, a brush and wet cloth are all that should be
needed.
• When steel forms are to be put in store or are not going to be used for some
time, they should be lightly oiled to prevent rusting.
• Timber and untreated plywood should also have a coat of release agent applied
for protection if they are not going to be re-used immediately.
• Any depressions, splits and nail holes should be repaired with plastic wood or
similar material, followed by a light rubbing down.
• Before concreting, the insides of the forms should be cleaned. Where the forms
are deep, temporary openings should be provided for inspection.

Clean and store reusable form panels and components

Company Rules and Regulations

Stripping formwork can be one of the most hazardous phases of concrete
construction. While falling objects are the primary hazard, there may also be fall hazards
as a result of floor collapse and manual tasks hazards from a person working in awkward
postures, repetitive handling of materials and limited task variety. As with formwork
erection, the stripping operation must be carried out in an orderly, progressive manner.

B. Exclusion zone

Only persons involved in the stripping operation should be permitted in
the area to be stripped. Stripping are as should be cordoned off and signs should be
displayed. The signs should require persons to keep out of the area.

Danger

FORMWORK STRIPPING IN PROGRESS
AUTHORISED PERSONS ONLY

It is preferable to restrict access to the whole floor where soffit is taking place
and this should reduce the quantity of signage and barricades required. Where other
trades are required to work on the same floor during stripping of walls, columns or small
sections of soffit, the principal contractor or employer should ensure that stringent
controls are applied that prevent other persons from entering the stripping area.

C. Removal of the formwork
The period for which forms should be left in place depends upon the

temperature of air, the shape and position of structural member (i.e. horizontal vertical
or inclined), the nature of the loads likely to come and the character of the cement and
cement paste. Generally, the use of rapid hardening cement, higher temperatures, low
water cement ratio and lighter loads, will permit early removal of formwork. Under
normal conditions where temperature is above 20ºC and ordinary cement is use, forms
may be removed after the expiry of the period given below:

Particulars of the structural Period of removing of member formwork
24 to 48 hours
a) Vertical sides of slabs, beams
columns and wall 3 days

b) Slabs (props or vertical
supporting member left
under)

c) Beams soffits (props left 7 days
under)

7 days

d) Bottom of slabs up to a span
of 4.5 m.

e) Bottom of slabs above 4.5 m 14 days
span, bottom of the beams up
to 6 m span, and bottom of
arch ribs up to 6 m span

f) Bottom of beams over 6 m span and 21 days
bottom of arch ribs

over 6 m span