Formwork in construction - the ultimate guide for builders (2023)

Specificbuildis a common activity on most construction sites around the world, one of the crucial activities to ensure concrete gets where it needs to be.formwork.This manual provides information on the design, installation, use and dismantling of formwork.

What is the definition of formwork?

Formwork means the surface of formwork and reinforcement used to contain and shape wet concrete until it is self-supporting.

Formwork includes the formwork over or into which concrete is poured, and the structures and struts that provide stability. Although commonly referred to as part of the formwork structure, beams, girders, struts, footings, and foundations are technically referred to as formwork.

Construction formwork can involve high-risk activities such as operating powered mobile installations such as cranes, working at heights and digging foundations.

Safe Working Method Statements (SWMS)

If the work involves high-risk construction work, a SWMS should be developed in consultation with workers and their representatives who carry out high-risk construction work as defined in the Work Environment (WHS) Regulations.

A statement of safe work practices is a document that describes the steps in which a task must be performed and the risks and controls necessary to make the work safe.

Design formwork systems

The design of the final concrete structure can greatly affect the convenience of formwork construction and human health and safety during construction. In general, the simpler and simpler the final concrete construction is, the safer it will be to construct, erect and dismantle the formwork.

An experienced formwork designer should be consulted when designing cast-in-place concrete structures, so that health and safety risks during formwork construction and removal can be factored into the design.

The formwork designer must be proficient in formwork design, including documentation of temporary work platforms and specialized equipment needed to safely construct formwork on site.

A designer may apply a technical standard or a combination of standards and technical principles relevant to the design requirements, provided the result is a design that meets the legal requirements.

The formwork must be:

• rigid, watertight, reinforced and bonded to maintain position and shape during construction, and
• they can be removed easily and safely without damaging the formed concrete, or have components that remain part of the finished structure so that the rest can be removed without damaging the structure.

Formwork drawings must include details of:

• formwork and formwork joints
• sealing procedures
• tire
• frame size and spacing
• details of accessories or proprietary systems proposed to be used and
• circuit breakers, if used.

The formwork designer must determine vertical leakage rates for walls, columns, and other vertical concrete members before finalizing the formwork design.

Information on construction method and assembly sequence, if relevant, should be included in the formwork drawings. When dealing with special methods, such as external vibration, the formwork design must take into account any additional structural loads.

When the formwork is reused, the formwork design must ensure that it retains its shape after taking into account the deterioration of the materials during use, handling and storage.

All formwork designs must be certified according to current legislation. Components from different formwork systems must not be mixed unless a competent person, e.g. an engineer, has approved the use of the components. Variations in a system design must be checked and verified in writing by a designer, engineer or other competent person.

Slide, grab and fall

The design of the permanent structure affects the risk of injury from slips, trips and falls (and falling objects) during formwork construction and use. Although often not reasonably practicable, design measures for permanent structures that can mitigate these risks include:

• reduce variations in pattern depth so you have a uniform depth. Formwork decks with constant depth are easier to erect than decks with variable depth and minimize the risk of damage. Deeper joists introduce "drops" into the floor, creating trip and fall hazards and requiring more work to build and remove after a leak
• beams designed to provide easy access over the beam recess to prevent workers from entering the formwork during construction
• reducing the number of columns required and where columns exist, eliminating capitalization and dropdowns, and
• reduction of cantilevered floor sections.

The design of formwork systems can also reduce the risk of slipping, tripping and falling by providing adequate safe access and protection against falls and falling objects.

manual tasks

The design of formwork systems can reduce the amount of manual handling required for formwork operations. To reduce the risk of manual handling, use:

• prefabricated columns and beams to minimize the need for reinforcement, erection and dismantling of column formwork and casting on site – operations carried out in a factory environment are generally less risky
• table top or floating forms - a large pre-assembled shuttering and formwork unit, often forming a complete floating floor slab bay, and
• modular formwork systems that are generally lighter and eliminate the need for tasks such as repetitive hammering.

Types of formwork in construction

When choosing a formwork system for a particular task, consideration must be given to the safety of workers who assemble, use and dismantle the formwork. In particular, consider stability, strength and risk of falls, falling objects and manual tasks. The best proprietary systems have built-in safety features to manage the risk of falls and dangerous manual tasks.

Traditional formwork systems (multiplex formwork)they are usually made on site from wood or plywood and supporting elements such as scaffolding.

When using a traditional system, a standard formwork construction with a known tested load capacity should be used whenever possible. Standard structures can minimize the risk to workers who collect and separate forms and handle and store materials.

Modular form systems(aluminum formwork/steel formwork) is specially designed and manufactured off-site. Modular systems usually have their own formwork components and nominal load calculations prepared by the manufacturer and are usually made from hardboard, plastic, steel and aluminum products. Most formwork systems use two or more materials, for example plywood versus steel framing for wall panels.

Modular systems are generally lighter and require less physical effort than traditional systems. This minimizes the risk of injury from manual tasks. However, due to their lower weight, modular systems may be more prone to tipping over during system setup due to factors such as wind loads. This is usually only a problem before the formwork deck is placed in the modular system. To effectively control this problem, the modular formwork system must be reinforced gradually during assembly according to the supplier's instructions.

Formwork systems – Formwork for walls and columns

Wall and column forms must be designed to withstand wind loads before, during and after casting. Strings and forms cannot be removed from the casting element until it can safely withstand possible shocks and wind loads.

Vertical members can be laterally supported in a variety of ways, including horizontal and angle bracing and structural connections to other parts of the building. The design of a support element must be carried out by a competent person.

The reinforcement element must also be able to withstand tensile and compressive loads that can be exerted by wind. Anchors for hangers are preferably countersunk anchors or "through bolts" which extend on both sides of the anchoring means. Drill anchors of the following types may be used, provided they are installed in accordance with the manufacturer's instructions:

• Submersible anchors that do not rely on friction to function.
• Non-slip expansion anchors and guided by high load torque. These anchors have a working load of at least 60% of the initial sliding load and are generally suitable for structural tensile loads.
• Spiral Bolts - The proper functioning of spiral bolts is highly dependent on installing them according to the manufacturer's specifications, for example drilling the correct size hole and applying the correct torque to the concrete.

Observation:Some jurisdictions may not accept this type of installation, so check with your WHS regulator.

Drill anchors must be installed in accordance with the manufacturer's instructions.

They should be tightened with a torque wrench or some other reliable method of torque control, for example a calibrated 'ratchet gun'. Written records should be available at the jobsite confirming the setting time of drill anchors.

Access platforms for wall and column formwork

There must be adequate access to wall and column forms and may include:

• mobile scaffolding
• specifically constructed access platforms, or
• lifting work platforms.

Edge protection must be provided on access platforms. Preferred methods of access to platforms are ladder access or, if impractical, safe industrial ladders.

The access method must accommodate one person and be placed at a height and distance from the form to minimize effort and movement of the person. The concrete casting system must provide enough space for one person to stand with edge protection. Where a stair access goes through a formwork deck,preventor porters must not stick out over the stairs.

Platforms must also be designed to withstand loads that may be applied during concrete pouring to ensure that the platform does not collapse or tip over. They may need to be tied or weighted, especially aluminum scaffolding, which may not support its own weight to prevent it from tipping over.

Mobile work platforms must have their wheels locked, except when moving the mobile platform.

Access system on the right

The designer must ensure that a longitudinal access system can withstand the loads applied to it, including windy conditions and an emergency evacuation situation. Both the system itself and the formwork must withstand the loads exerted by the access system.

Lifting methods for wall and column formwork

Wall and column forms must be provided with designed lifting points. Design drawings must confirm this. Drilling holes in the formwork on site is not recommended as this may damage the formwork, provide insufficient lifting points and make it difficult to attach lifting equipment.

Wall and column forms can only be lifted with a form-locking lifting system, e.g. lifting eyes or by rotating the lifting straps around the formwork so that the formwork does not slip off the straps. Specially designed lifting eyes should be used instead of lifting the load, as there is less risk of the load accidentally being released from the crane hook.

If lifting eyes are fitted to the formwork, they must be fitted in accordance with the design.

Placement of formwork frames

Formwork structures should be built gradually to ensure the safety of the installers and the stability of the overall structure.

Brackets should be attached to frames as soon as possible and designated access routes should be marked with flag lines or other means.

If side braces or other edge protection are gradually installed in formwork structures, other control measures to prevent falls may not be necessary.

Many conventional formwork structures consist of diagonal braces that intersect in the middle. Although these brackets are not considered sufficient edge protection for a complete formwork deck, they can provide reasonable fall protection during frame erection. This is only the case when the brackets are installed gradually when the frames are installed.

As the height of formwork frames increases, there is a greater need for lateral stability in the frames. Ensure that the construction, including support, is carried out in accordance with the manufacturer's design documentation and site instructions. Formwork installers must be trained to install the formwork safely.

The risk of internal falls during gantry assembly can be controlled by completely covering each elevation of the formwork decks and false decks. This involves:

• install a full deck of scaffold planks or other suitable deck on each elevator
• set the deck on the next lift while on a full-deck platform and
• leaving each elevator fully in place until removed.

When disassembling an elevator, the deck must be removed while on a full-deck platform directly below it.

Formwork systems – Suspended boards

Where the next formwork deck requires people to stand at a height of 2 meters or more above the finished formwork deck to install beams and joists for the next formwork deck, a continuous 'false' deck which is a complete deck of the same area if the floor is formed, must be provided.

This cover must be fitted both inside and between the formwork frames and is usually made ofsteigershelves or modular platform sections.

A protected entry opening can be left in the deck to allow lifting of materials. Using a fixed platform system is preferable to overlapping planks because a fixed system cannot accidentally detach. Overlapping planks can only be used if they are secured against lifting and sliding.

The false deck should be constructed so that there are no large gaps and only gaps where a vertical section of a frame passes through the deck (see Figure 1). Openings must not be larger than 225 mm.

A dummy deck must be able to withstand the expected load of workers and materials during construction and persons or objects that may fall onto the deck. Access must be granted to each of the dummy tires.

When considering deck design for erecting, altering, or dismantling the formwork, the dummy deck weight and live load must be applied to the formwork support.

The height between the dummy platform and the pouring platform must allow access for one person during stripping. Workers must reasonably ensure their own safety by not climbing the structure.

intermediate platforms

With a possible drop distance of less than 2 metres, an intermediate work platform with a minimum width of 450 mm can be supplied (see figure 2).

install conveyors

Beams are the main horizontal support elements for a formwork deck placed on top of formwork frames. They are usually made of wood, but sometimes they are also made of metal. They must be placed by people on a safe platform no more than 2 meters below them.

Carriers must be positioned so that they do not fall off the top of the frames. The usual method of doing this is to place the supports in U-heads on top of the frames and minimize overhangs. U-heads should be used where two brackets abut each other. Where only a few beams are placed at the U-head, the beam should be placed centrally at the U-head unless directed otherwise by a formwork designer, engineer or other competent person. This can be achieved by turning the head into a U shape or using wooden wedges.

When the upper part of the support element is a flat board, the bracket must be nailed to the board or secured in some other effective way. Flat boards should only be used if specified by a formwork designer, engineer or other competent person.

Installation of beams to support formwork

Where a dummy deck is placed 2 meters or less below a worker, the joists may be spread across the joists with the worker on top at joist level.

If the height of the formwork deck to be built is more than 2m above a continuous deck or a surface below it, the beams must be spread from a platform 2m from that surface, below the deck to be built (See figure two ). This work platform must be a false deck, but an intermediate platform can also be used.

A person must have a working platform with a width of at least 450 mm (two planks) when the possible fall distance is less than 2 meters. It is not acceptable for one person to work on a single shelf or conveyor.

An example of a work system that can be used for this is the following:

• The beams are lifted from below by workers and spread on top of the beams to their estimated final positions while on a lower work platform.
• The below-deck platform must be located at a height suitable for handling beams without presenting risks from manual tasks and not exceeding 2 meters above the continuous deck or surface below.

Lie formally on the deck

A formwork board should be placed gradually so that people have a method to prevent falling under the board.

This control measure is particularly important in situations where a false roof is not installed less than 2 meters below the level of the roof to be laid. Formally, in this situation it is only allowed to spread on the accompanying support beams:

• People start placing the perimeter scaffold formwork boards or other supplied edge protection on the perimeter of the formwork.
• At least four beams with a distance of 450 mm - 400 mm apart, a total of 1.8 m - are in beams close to the person, and in the other direction the beams extend for at least

1.8 meters (see figure 3). Therefore, if a person falls, he falls into the rafters and must be prevented from falling further. In some situations, there is a possibility that a person could fall through the rafters if the rafters spread when the person's body made contact. To

it is more likely to be a potential hazard if the person falls into the rafters in the same direction as the rafters. Implementing controls to minimize lateral movement of the beams will minimize this possibility.

• People place the form in front of their body, so if they trip, there's a good chance they'll land on top of the sheets being placed.

If there is a leading edge and the distance below the deck to be built is greater than 2 metres, the SWMS must indicate how the work will be completed to manage the risk.

cantilevers

Cantilevered beams, joists and laminated slabs can be dangerous if not secured. The weight of the material or a person standing on the cantilever can cause the tree to sway and the person or material to fall. The use of cantilevers should be limited in the design of formwork systems

a minimum. In some situations, the use of cantilevered sections is unavoidable. In these cases, a formwork designer must consider the potential for people and stored materials to rotate cantilevers.

When a person's weight causes a cantilever arm to rotate, the formwork design must accommodate this.

measures to protect the cantilevers so that this does not happen. This can be temporary support, nailing, screwing or another effective method. If nailing is used, the formwork design must specify the nailing detail and this must be followed. This may include the use of specially designed or unique fittings. Materials should not be stacked or stored in an overhanging section unless the section is designed to support the load. Temporary cantilever work platformsclampFrames are a form of cantilevered scaffolding. When a person or object can fall more than 4 meters from a scaffold, personnel involved in erecting, altering or dismantling must have a scaffold permit. The minimum license class for this type of work is Intermediate Scaffolding.

penetrationer

Open transits such as stairs or transits to allow services to create hazards to persons on deck, for example a fall into major traffic, into minor traffic or an object falling through the opening onto persons below. An extension must be protected where there is a risk of a person or object falling.

Protect open penetrations with edge protection such as railings or by covering them tightly so that no one can fall. Concrete slab penetrations can include cast mesh as a backup system. The mask must have a small opening, e.g. a mask of 50 x 50 mm or less and be made of material that can withstand the possible applied loads. Where mesh or other physical fall protection material is to be installed for larger penetrations, this should be included in the slab design specifications to ensure that the slab can withstand potential loads, including people, equipment and materials.

Where holes are drilled in the mesh to allow supplies to pass through, the hole must be cut in the mesh profile so that the mesh remains in penetration and the mesh load capacity is not reduced below design specifications.

The isolated use of plywood roofing is not satisfactory risk management because:

• cover is indistinguishable from other plywood pieces
• cannot be reverted without major changes once the first service is installed
• it can be difficult to determine whether plywood is properly secured and
• secure plywood covers can be removed for access and not re-tightened.

Plywood cladding must be structurally graded, painted in a light color and marked with text, e.g. "Danger of Penetration below". The roof must be solidly attached to the concrete and designed for possible loads that may occur, for example workers, materials or installations that may pass over the roof.

Before stripping the formwork, cover the penetration that will be exposed when the formwork is stripped, or protect the penetration before stripping.

Feedthroughs are also dangerous before deck placement. Beams placed to the edge of the transit must be secured so that the tree does not spread if someone falls on it.

Workstations for steel fasteners and others

Steel fixers, plumbers and electricians usually follow close behind the formwork. The formwork area must be large enough to ensure that these persons are clearly separated from the formwork workers.

A formwork zone should be maintained behind the leading edge. This zone must be clearly marked with signs and a chain link fence. Figure 4 shows the 'other work' zone, the 'formwork' zone and the area retained for edge protection - four beams spaced 1800mm from the laid deck.

Temporary walkways placed over the reinforcing mesh can be used to manage the risk of slips and trips when multiple vessels enter large areas where the reinforcing mesh is placed behind the formwork.

A physical barrier must be installed and maintained to separate the formwork work area from other workers. This barrier must be rigid, able to maintain its integrity in the upright position and support signage when necessary.

changing floors

Formwork decks are rarely flat across the entire floor, usually due to deep or "overhanging" beams, sometimes called "capitals" around the columns. Uneven floors present a trip hazard.

These risks are most effectively managed by ensuring that formwork and deck supports are gradually built up to the lower deck areas before work begins on the upper deck areas.

Fall protection of formwork decks

During the construction of formwork, the construction is constantly changing, so the constant change offall protection measuresit is also necessary.

If there is only one front edge, the other edges are equipped with scaffolding edge protection or safety screens, so the fall protection of the front edge is relatively simple. However, when there are multiple leading edges or the tire is not at a uniform level, fall protection can be difficult to implement.

Edge protection on formwork decks

When formwork design is complex, it may be impractical to provide edge protection on the leading edges because the deck profile is constantly changing and building edge protection would create more risk than it would control. For example, people installing edge protection may take risks when installing edge protection.

In some situations it may be necessary to protect the edges of the formwork deck.

Examples where edge protection must be placed are:

• where there is a change in deck height along the side of the deck to be built, i.e. an overhang beam and no beam or framing at the different height
• when a leading edge must be left unattended and access to the deck is required by someone other than the formwork, i.e. the formwork deck is not sealed and marked with 'keep out' signs, and
• in openings in stairwells or elevator shafts.

Perimeter screens or scaffolding are an effective means of edge protection on a finished formwork platform. Scaffolding should be placed in front of the formwork and prevent workers from falling off the finished board. The biggest advantage of these systems is people

they do not need to install edge protection around the formwork deck and are therefore not at risk of falling. The other benefit is edge protection for people installing the final perimeter after the boards are already in place.

When suspended, cantilevered, cantilevered or suspended scaffolding is used, or any scaffold from which a person or object can fall more than 4 meters from the platform or structure, any assembly, alteration or disassembly of the scaffold must be carried out by qualified scaffolders. Cover gaps between finished floor and scaffolding after formwork is removed if there is a risk of people or materials falling through the gap.

In some situations it may be impractical to provide perimeter screens or scaffolding. Use a work system to install deck edge protection that eliminates or minimizes the risk of falls.

Harness systems should not be used as they do not provide practical control of the risk of falling from a height from the perimeter of the formwork.

If necessary, the edge guard can be replaced with an alternative measure, provided that this measure prevents a person from falling over the edge. An alternative is to build a barricade

6 feet behind the rim with clearly visible warning signs.

Perimeter containment screens

Perimeter guards are protective structures attached to the perimeter structure or work platform to prevent objects and people from falling outside the work area. This greatly minimizes the risk of injury to other workers and the public.

Screens should be used throughout the construction process, especially when placing or removing formwork. They are usually covered with wood, plywood, metal or synthetic mesh.

Screens can be supported by the building or structure or by specially designed scaffolding. Screens can tooat handleas a perimeter lifeline on an upper work platform and must extend at least 2 meters above the work surface to provide protection to the public and workers outside the contained work area.

When choosing embedded monitors, consider:

• the ability to withstand or contain applied shock loads, including construction materials, equipment and debris
• resistance to wind loads on the supporting structure
• inspection frequency
• chemical reactivity including flammability
• ventilation requirements
• requirements for light transmission
• degree of protection against rain or washing
• pattern and frequency of attachment points, and
• openings created by a fixation method.

Containment screens should be left in place from the beginning of the formwork being placed until the removal of the bottom piece is completed to prevent objects from falling into the process.

To prevent the material from falling, the gaps between the perimeter screens and the formwork deck or floor must not exceed 25 mm.

Removal of formwork systems

Preload inspection and certification of formwork systems

Inspection and certification processes contribute to risk management during formwork and formwork construction.

Inspections and stress releases should be carried out at key stages of the formwork construction, including when the formwork is under load, for example with prestressed formwork components, equipment or cables, and before completion.

A separate certification process must take place when the formwork is complete and before pouring concrete.

A competent person, such as an engineer experienced in structural design (certifying engineer), should inspect and certify that the completed formwork meets the construction specifications and is structurally sound prior to loading. In general, certification is not required for formwork and panels in residential construction.

The certifying engineer must complete and provide a formwork construction certificate

to whoever manages or controls the formwork, often the main contractor. An example is in Appendix A.

Where scaffolding is used, there are specific requirements for control of access to the scaffold and for inspection and certification prior to use.

Load formwork systems

The formwork should not be loaded until it is confirmed that it meets the construction specifications, for example by carrying out a precast inspection prior to placing the concrete.

Loads must not exceed the structural load specified by the designer.

To maintain the stability of the formwork, the placement of the concrete must not exceed the calculated maximum flow rate and the inner part of the formwork must be placed before proceeding with a cantilever section.

Lifting, pumping and other equipment must not be attached to the formwork unless specifically permitted by the formwork construction.

The formwork shall be checked while under load for signs of possible failure or collapse and to verify that vertical and horizontal movements do not exceed specifications.

Monitoring and inspection of formwork systems

A designated competent observer must continuously monitor the form during concrete placement and must have an appropriate communication system in place to alert others in an emergency.

Except for a designated observer, no one should be under a formwork platform while concrete is being placed. An observer should not be directly under an area where wet concrete is placed in the mold.

During casting, competent persons must be available to carry out adjustments or emergency repairs. Concrete pouring must be stopped during adjustments and repairs.

formwork certifications

After the concrete has hardened and before blasting begins, a competent person, for example an engineer experienced in structural design, should confirm in writing that the permanent structure is self-supporting and that the formwork can be removed. The certification shall be based on the structural design specifications, the verification of the strength of the concrete mix and the time elapsed since execution.

Documentation from the concrete supplier confirming the specific specification must be available upon request. There must be a concrete sampling and testing procedure to verify that the concrete meets the design specifications.

A competent person should also provide information to the SWMS about stripping to ensure that the permanent concrete member does not fail and result in structural collapse.

strip formwork

As with the installation of formwork, dismantling must be carried out in a clear, systematic and progressive manner, taking into account the risks of falls, falling objects and hazards associated with manual tasks in the now closed space.

When assessing the risk of stripping, consider:

• the number of people on the strip crew
• the sequence of stripping activities - must describe how to remove the frames and other supports, i.e. how far the U-heads must be lowered
• whether the support system is completely removed in an area before the formwork deck is removed, or whether the supports are lowered slightly but remain under the formwork while it is being removed
• remove sharp nails and fasteners before stacking components
• minimize damage to components
• stack formwork components – do not block access routes or work areas
• formwork components do not fall from a building or structure
• flat heads do not support carrier ends
• when a rear stowage is required or only part of the support system needs to be removed, how the structural elements will be held in place and the type and layout of elements to replace the formwork system
• other special requirements in connection with blasting and/or construction, e.g. control of chip removal after post-tensioning
• provide lighting for the workplace and the surrounding area, and
• house maintenance, removing nails and scrap, stacking stripped forms and removing tripping hazards, for example concrete nails and floor support anchor posts.

Removal of formwork must be carried out systematically, so that the deck is gradually removed as a support system. Mold can be removed by partially lowering the support system and then dropping the deck segment (sail) onto the support system. This eliminates the need to manually lift leaves from the ground.

Reduction of liabilities

Formwork removal is easier when the strength of the bond between the formwork material and the concrete is reduced. Adhesion depends on material properties and the softness of the impression material. Liquid joint breaker can be used on wall and column forms to reduce joint strength, but use on floor forms is not recommended as it can create a slip hazard.

licorice pickle

Drop stripping describes the method used when the entire support system is removed from the formwork and the formwork is then lowered to a lower level by its own weight or by people lifting it.

Drip staining should not be used. It can be very dangerous as the mold can get out of control and reach people close to work.