Concrete construction is a common activity found on most jobsites throughout the world, one of the critical activities that goes into making sure that the concrete ends up where it needs to be is formwork. This Guide provides information on designing, erecting, using and dismantling formwork.
If you are looking for more details, kindly visit our website.
Formwork means the surface of the form and framing used to contain and shape wet concrete until it is self-supporting.
Formwork includes the forms on or within which the concrete is poured and the frames and bracing which provide stability. Although commonly referred to as part of the formwork assembly, the joists, bearers, bracing, foundations and footings are technically referred to as falsework.
Formwork construction may involve high risk activities like operating powered mobile plant like cranes, working at height and excavating foundations.
If the work involves high risk construction work, a SWMS must be developed in consultation with workers and their representatives who are carrying out the high risk construction work as defined under the Work Health and Safety (WHS) Regulations.
A safe work method statement is a document which outlines the steps in which a task needs to be performed and the hazards and controls necessary to help make the work safe.
The design of the final concrete structure can have a major effect on the ease of formwork construction and the health and safety of people during construction. Generally the more basic and simple the final concrete structure, the safer it is to construct, erect and dismantle the formwork.
An experienced formwork designer should be consulted during the design of in-situ concrete structures to enable the health and safety risks during formwork construction and dismantling to be considered in the design.
The formwork designer must be competent in formwork design including documenting temporary work platforms and special equipment needed for safe formwork construction on-site.
A designer may use a technical standard or a combination of standards and engineering principles relevant to the design requirements as long as the outcome is a design that meets regulatory requirements.
Formwork should be:
Formwork drawings should include details of:
The formwork designer should determine the vertical pour rates for walls, columns and other vertical concrete elements before completing the formwork design.
Details of the construction method and erection sequence should be included on the formwork drawings where appropriate. Where special methods like external vibration are involved the formwork design should allow for any resulting additional structural loads.
Where formwork is to be re-used, the formwork design should ensure form strength is retained after allowing for the deterioration of materials through use, handling and storage.
All formwork drawings should be certified as complying with applicable laws. Components from different formwork systems should not be mixed unless a competent person, for example an engineer, has authorised the component use. Variations to a design of a system should be checked and verified in writing by a designer, engineer or other competent person.
The design of the permanent structure affects the risk of injury from slips trips and falls (and from falling objects) during formwork construction and use. While often not reasonably practicable, permanent structure design measures that can reduce these risks include:
The design of formwork systems can also reduce the risk of slips trips and falls by providing adequate safe access and fall and falling object protection.
The design of formwork systems can reduce the amount of manual handling required in formwork activity. To reduce manual handling risks use:
The safety of workers erecting, using and dismantling the formwork should be considered when choosing a formwork system for a particular job. In particular consider stability, strength and the risk of falls, falling objects and manual tasks. The best proprietary systems have integrated safety features to help control the risk of falls and hazardous manual tasks.
Traditional formwork systems (plywood formwork) are typically constructed on-site from timber or plywood and supporting elements like scaffolding.
When using a traditional system, a standard formwork frame with a known tested loading capacity should be used wherever possible. Standard frames can minimise the risk to workers erecting and dismantling the formwork and handling and storing materials.
Modular formwork systems (aluminum formwork / steel formwork) are specially designed and manufactured off-site. Modular systems usually have proprietary formwork components and rated load calculations set out by the manufacturer and are often made from hardboard, plastics, steel and aluminium products. Most formwork systems use two or more materials, for example plywood facing to steel frames for wall panels.
Modular systems are often lighter weight and require less physical effort than traditional systems. This minimises the risk of injury resulting from manual tasks. However because of their lighter weight, modular systems may be more susceptible to falling over when erecting the system due to factors like wind loading. Generally this will only be an issue before placement of the formwork deck on the modular system. To effectively control this issue the modular formwork system should be progressively braced in accordance with the suppliers instructions during its erection.
Wall and column forms should be designed to withstand wind loading before, during and after the concrete pour. The bracing and forms should not be removed from the cast element until it can safely withstand potential impact loads and wind loads.
Lateral support can be provided to vertical elements in a variety of ways including horizontal and angled braces and structural connections to other parts of the building. A bracing element design should be completed by a competent person.
The bracing element should also be able to resist both tensile and compressive loads that may be applied by the wind. Anchors for braces should preferably be cast-in type anchors or ‘through-bolts’ extending through both sides of the anchoring medium. Drill-in anchors of the following type may be used provided they are installed in accordance with the manufacturer’s instructions:
Note: Some jurisdictions may not accept these types of installations, so check with your WHS regulator.
Drill-in anchors should be installed in accordance with the manufacturer’s instructions.
They should have their torque set using a torque wrench or other reliable method to verify the torque, for example a calibrated ‘rattle gun’. Written records verifying the setting torque for drill-in type anchors should be available at the workplace.
Suitable access should be provided for wall and column forms and may include:
Edge protection should be provided on the access platforms. Preferred methods of entry to platforms include stair access systems or if this is not practicable secured industrial ladders.
The entry method should allow room for a person and be positioned at a height and distance from the form to minimise a person’s effort and movement. The concrete pouring system should permit enough space for a person to stand with edge protection provided. Where stair access passes a formwork deck, joist or bearers should not protrude over the stairs.
Platforms should also be designed to resist loading that may be applied during a concrete pour to ensure the platform does not collapse or overturn. They may need to be tied in or counter weighted, particularly aluminium scaffolding which may not have the self-weight to prevent overturning.
Mobile work platforms should have their castors locked, except when relocating the mobile platform.
The designer should ensure a trailing access system can support the loads that will be applied to it including wind conditions and an emergency evacuation situation. Both the system itself and the form should be able to withstand applied loads from the access system.
Wall and column forms should be provided with designed lifting points. Design drawings should confirm this. Cutting holes in the form in-situ is not recommended as this can damage the form, be inadequate lifting points and make it difficult to safely attach lifting gear.
Wall and column forms should only be lifted with a positive lifting system, for example lifting lugs or by slinging the lifting slings around the form so the form cannot slip out of the slings. Purpose designed lifting lugs should be used instead of slinging the load because there is less risk of the load becoming inadvertently disconnected from the crane hook.
Where lifting lugs are attached to the form they should be attached in accordance with the design.
Formwork frames should be erected progressively to ensure the installers’ safety and the stability of the overall structure.
Braces should be attached to the frames as soon as practicable and designated access ways should be indicated by using bunting or by other means.
If side bracing or other edge protection is installed progressively on formwork frames other control measures to prevent a fall occurring may not be required.
Many conventional formwork frames consist of diagonal braces that cross in the middle. While these braces are not considered to be suitable edge protection for a completed formwork deck, they may provide reasonable fall protection during frame erection. This is only the case where braces are installed in a progressive manner as soon as the frames are installed.
As the height of formwork frames increase there is a greater need to provide lateral stability to the frames. Ensure framing, including bracing, is carried out in accordance with on-site design documentation and manufacturers’ instructions. People erecting formwork must be trained to erect formwork using safe methods.
The risk of internal falls while erecting frames can be controlled by fully decking each lift of the formwork decks and false decks. This involves:
During dismantling of a lift, decking should be removed while standing on a fully decked platform immediately below.
Where the next formwork deck would require people to stand at heights of 2 metres or more above the finished formwork deck to install bearers and joists for the next formwork deck, a continuous ‘false’ deck, which is a full deck the same area as the floor being formed, should be provided.
This deck should be provided both inside and between formwork frames and typically consist of formply, scaffold planks or modular platform sections.
A protected entry opening can be left in the deck to enable materials to be lifted. Using a captive platform system is preferable to lapped planks because a captive system cannot be accidentally dislodged. Lapped planks may only be used if secured against uplift and slipping.
The false deck should be constructed so there are no large gaps and gaps only exist where a vertical member of a frame passes through the deck (see Figure 1). Gaps should not exceed 225 mm in width.
A false deck should be able to support the expected load of workers and materials during construction and people or objects that could fall onto the deck. Access should be provided to each of the false decks.
When considering the design of the deck for erecting, altering or dismantling formwork, the weight of the false deck and live load should be applied to the formwork support structure.
The height between the false deck and the pouring deck should allow entry for a person during stripping. Workers must take reasonable care for their own safety by not climbing the framework.
Where the potential fall distance is less than 2 metres, an intermediate work platform can be provided that is at least 450 mm wide (see Figure 2).
Bearers are the primary horizontal support members for a formwork deck that are placed on top of formwork frames. They are usually timber but are sometimes metal. They should be placed in position by people located on a secure platform no more than 2 metres below them.
Bearers should be positioned so they will not fall off the top of the frames. The usual method to do this is by placing the bearers in U-heads on top of the frames and by minimising cantilevers. U-heads should be used where two bearers abut. Where only single bearers are placed in the U-head, the bearer should be placed centrally in the U-head unless a formwork designer, engineer or other competent person states otherwise. This can be achieved by rotating the U-head or by using timber wedges.
Where the top of the supporting member consists of a flat plate, the bearer should be nailed or otherwise effectively secured to the plate. Flat plates should only be used where specified by a formwork designer, engineer or other competent person.
Where a false deck is provided at 2 metres or less below a worker, joists may be spread on the bearers with the worker standing on top at bearer level.
If the height of the formwork deck being constructed is more than 2 metres above a continuous deck or surface below it, joists should be spread from a platform located within 2 metres of that surface, underneath the deck being constructed (see Figure 2). This work platform should be a false deck but an intermediate platform may be used.
A person should be provided with a working platform at least 450 mm wide (two planks) when the potential fall distance is less than 2 metres. It is not acceptable for a person to work from a single plank or bearer.
One example of a work system that may be used to do this is as follows:
A formwork deck should be laid in a progressive way so people will be provided with a method to prevent them from falling below the deck.
This control measure is particularly important in situations where a false deck has not been provided within 2 metres below the level of the deck to be laid. In this situation formply may only be spread on the joists provided:
1.8 metres (see Figure 3). Therefore, if a person falls they will fall onto the joists and should be prevented from falling further. In some situations, there may be a possibility of a person falling through the joists if the joists spread as the person’s body makes contact. This
is more likely to be a potential hazard when the person falls onto the joists in the same direction as the joists. Implementing controls to minimise sideways movement of joists will minimise this possibility.
Where a leading edge is involved and the distance below the deck being constructed is greater than 2 metres the SWMS must detail how work will be completed to control the risk.
Cantilevered bearers, joists and ply sheets can be hazardous when left unsecured. The weight of material or a person standing on the cantilever may make the timber see-saw and cause the person or material to fall. When designing the formwork system, the use of cantilevers should be kept to
a minimum. In some situations using cantilevered sections is unavoidable. In these cases, a formwork designer should consider the potential for people and stored materials to cause cantilevers to pivot.
Wherever the weight of a person will cause a cantilever to pivot, the formwork design should include
measures to secure the cantilevers so this will not occur. This may include temporary propping, nailing, bolting or another effective method. If nailing is used the formwork design should specify the nailing detail and this should be followed. This may include the use of purpose designed or proprietary brackets. Materials should not be stacked or stored on a cantilever section unless the section has been designed to carry the load. Temporary working platforms cantilevered from shoring frames are a form of cantilevered scaffold. Where a person or object could fall more than 4 metres from a scaffold, workers involved in erecting, altering or dismantling them must hold a scaffolding licence. The minimum licence class for this type of work is Intermediate Scaffolding.
Open penetrations like stairwells or penetrations to allow for services create hazards for people on the deck, for example a fall through a larger penetration, stepping into a smaller penetration or an object falling through the opening onto people below. A penetration where there is a risk a person or an object could fall through should be guarded.
Protect open penetrations with edge protection like handrails or by securely covering them so no one can fall through them. Penetrations in concrete slabs may include cast-in-mesh as a back-up system. The mesh should be of a small aperture, for example 50 x 50 mm mesh size or smaller and made of material capable of withstanding the potential imposed loads. Where mesh or other physical fall protection material is to be provided for larger penetrations this should be included in the slab design specifications to ensure it can withstand potential loads including those applied by people, equipment and material.
Where holes are cut in the mesh for services to pass through the hole should be cut to the profile of the service so the mesh remains in the penetration and the load carrying capacity of the mesh is not reduced below design specifications.
Using plywood covers alone is not a satisfactory risk control because:
Plywood covers should be structurally graded, painted in a bright colour and marked with wording, for example ’Danger penetration below’. The cover should be firmly secured to the concrete and designed for potential loads that may be applied, for example workers, materials or plant that may travel over the cover.
Before stripping formwork, cover the penetration that will be exposed as the formwork is stripped or protect the penetration before starting the stripping operation.
Zolo Product Page
Penetrations are also hazardous before the deck is laid. Joists placed up to the edge of the penetration should be secured so the timbers cannot spread if a person falls on them.
Steel fixers, plumbers and electricians often follow closely behind the formwork erection. The formwork zone should be large enough to ensure these people are clearly separated from the form workers.
A ‘formwork only’ zone should be maintained behind the leading edge. This zone should be clearly marked by signs and a mesh barrier. Figure 4 shows the ‘other work’ zone, the ‘formwork’ zone and the area retained as edge protection—four joists spaced 1800 mm beyond the laid deck.
Temporary walkways laid across reinforcement mesh can be used to control the risk of slips and trips when multiple trades are entering large areas where reinforcement mesh has been laid behind formworkers.
A physical barrier should be provided and maintained to separate the formwork work zone from other workers. This barrier should be rigid, capable of maintaining its integrity in an upright position and capable of supporting signage if required.
Formwork decks are rarely flat across the entire floor, generally due to deep beams or ‘drop downs’ sometimes called ‘capitals’ around columns. Uneven floors introduce fall hazards.
These hazards are most effectively managed by ensuring formwork supports and the deck are progressively constructed for the lower parts of the deck before work starts on the higher- level areas of the deck.
During formwork construction the structure is constantly changing so continual modification of fall protection measures is also necessary.
When there is only one leading edge where the other edges are provided with scaffold edge protection or safety screens, providing fall protection on the leading edge is relatively straightforward. However, where there are multiple leading edges or the deck is not at one consistent level, fall protection may be difficult to implement.
Where the design of the formwork is complex, it may be impractical to provide edge protection on leading edges because the profile of the deck is constantly changing and constructing leading edge protection would create more hazards than it would control. For example, the people installing the edge protection could be exposed to risks when installing the edge protection.
In some situations it may be necessary to provide perimeter edge protection on edges of the formwork deck.
Examples where edge protection should be installed are:
Perimeter containment screens or a scaffold are effective means of edge protection on a completed formwork deck. Scaffolding should be erected before the formwork and prevents workers falling off the completed deck. The main advantage of these systems is people
are not required to install edge protection on the perimeter of the formwork deck and are therefore not exposed to a risk of falling. The other advantage is edge protection for people installing the final perimeter formply sheets is already in place.
Where suspended, cantilevered, spur or hung scaffold, or any scaffold from which a person or object could fall more than 4 metres from the platform or the structure is used, any erection, alteration or dismantling of the scaffold must be carried out by licensed scaffolders. Cover gaps between a completed floor and scaffold after the formwork is stripped if there is a risk of a person or materials falling through the gap.
In some situations it may be impractical to provide perimeter containment screens or scaffolding. Use a work system to install perimeter edge protection on the deck which eliminates or minimises the risk of a fall.
Harness systems should not be used because they do not provide a practical control for the risk of a fall from height from the perimeter of formwork.
If required, edge protection can be substituted with an alternative measure provided this measure prevents a person falling from the edge. One alternative is providing a barricade
1.8 metres back from the edge with clearly visible warning signs.
Perimeter containment screens are protective structures fixed to the perimeter structure or working platform to prevent objects and people falling outside the work area. This significantly minimises the risk of injury to other workers and the public.
Screens should be used throughout the whole construction process especially while erecting or stripping formwork. They are usually sheeted with timber, plywood, metal or synthetic mesh.
Screens may be supported by the building or structure or by a specifically designed scaffold. The screens can also act as perimeter fall protection on a top working platform and should extend at least 2 metres above the working surface to provide protection for the public and workers outside the contained work area.
When selecting containment screens consider:
Containment screens should remain in position from the start of the formwork being erected until soffit stripping is complete to prevent objects falling throughout the process.
To prevent material from falling below, gaps between perimeter screens and the formwork deck or floor should not exceed 25 mm.
Inspection and certification processes each contribute to controlling risks during the construction of formwork and falsework.
Inspections and clearance to load should occur at key stages during the construction of formwork including when formwork is being loaded, for example with formwork components, equipment or pre stressed tendons and prior to its completion.
A separate certification process should occur when the formwork is complete and prior to concrete being poured.
A competent person such as an engineer with experience in structural design (certifying engineer) should inspect and certify that completed formwork meets the design specifications and is structurally sound before it is loaded. Generally certification will not be required for formwork and falsework in housing construction work.
The certifying engineer should complete and provide a Formwork Structural Certificate
to the person with management or control of the formwork, often the principal contractor. An example is at Appendix A.
Where a scaffold is being used there are specific requirements to control entry to the scaffold and for inspection and certification prior to use.
The formwork should not be subjected to a load until it is confirmed as meeting the design specification, for example by completing a pre-pour inspection before placing concrete.
Loads should not exceed the design loading specified by the designer.
To maintain stability of the forms the placement of concrete should not exceed the maximum calculated pour rate and the inboard part of formwork should be placed before proceeding to any cantilever section.
Hoisting, pumping and other equipment should not be attached to the formwork unless specifically allowed for in the formwork design.
Formwork should be monitored as it is loaded to check for indications of potential failure or collapse and that vertical and horizontal movements do not exceed specifications.
A competent designated observer should continuously monitor the formwork assembly during concrete placing operations and be provided with an appropriate communication system to alert others in case an emergency arises.
Other than a designated observer, no person should be underneath a formwork deck during concrete placement. An observer should not stand directly underneath an area where wet concrete is being placed into the forms.
Competent persons should be available during concrete placement to carry out any emergency adjustments or repairs. The concrete placement should cease during adjustments and repairs.
Once the concrete is cured and before starting the stripping operation a competent person, for example an engineer with experience in structural design should provide written confirmation the permanent structure is self-supporting and the formwork can be removed. The certification should be based on the design specifications for the structure, the verification of the strength of the concrete mix and the time period elapsed since the pour.
Documentation from the concrete supplier verifying the concrete specification should be available on request. A concrete sampling and testing procedure should be in place to verify the concrete meets its design specification.
A competent person should also provide input into the SWMS on formwork stripping to ensure the permanent concrete element will not fail and result in structural collapse.
As with formwork erection, the stripping operation should be carried out in an orderly, systematic and progressive manner, considering the risks of falls, falling objects and manual task hazards in the now enclosed space.
When assessing the risks from stripping formwork consider:
Formwork removal should be carried out in a systematic way so the deck is gradually removed as the support system. Formply may be removed by partially lowering the support system and then dropping the segment of the deck (sheet) onto the support system. This eliminates the need to manually lift sheets of ply from ground level.
Stripping formwork is easier when the strength of the bond between the form material and the concrete is reduced. The bond will be dependent on the material characteristics and the smoothness of the form material. A liquid bond breaker can be used on wall and column forms to reduce the strength of the bond but use on floor forms is not encouraged because it can cause a slip hazard.
‘Drop stripping’ describes the method used when all of the formwork support system is removed and the formply is then allowed to drop to the level below either by its own weight or by people levering it off.
Drop stripping should not be used. It can be very hazardous because the formply is likely to fall uncontrolled and can hit people in the vicinity of the work.
Reading Time:
4
minutes
A Comprehensive Guide
Formwork is an essential element of any construction project that involves concrete. It is a temporary structure that supports the weight of freshly poured concrete until it hardens and gains enough strength to support itself. The process of formwork at Alumlight involves the use of a variety of materials, including timber, steel, plywood, aluminum, and plastic, depending on the specific requirements of the project.
Different types of formwork are used in construction, each with its unique advantages and disadvantages. For instance, timber formwork is easy to work with and is a cost-effective option for small to medium-sized projects. Steel formwork, on the other hand, is highly durable and can be reused multiple times, making it a better option for larger projects.
Similarly, plywood formwork is lightweight, easy to handle, and can be used for curved surfaces, while aluminum formwork is lightweight, durable, and can be easily assembled and disassembled. Plastic formwork is a relatively new addition to the market and is gaining popularity due to its lightweight and reusable nature. Understanding the different types of formwork and their suitability for different projects is essential for any construction professional.
Formwork is an essential component in the construction process, and it is used to support and shape the concrete as it sets. It is a temporary structure that is removed once the concrete has hardened. Formwork is used to create a specific shape or design, and it is crucial to ensure that the formwork is strong enough to support the weight of the concrete.
There are several types of formwork used in construction, including timber, steel, plywood, aluminum, plastic, and fabric. Each type of formwork has its advantages and disadvantages, and the choice of formwork depends on several factors, including the type of project, the strength and surface quality required, and the durability of the formwork.
The choice of material for formwork is critical since it affects the strength, surface quality, and durability of the finished product. Steel formwork is the most durable and can be used for multiple projects. Wood and plywood are cheaper and easier to use but have a shorter lifespan. Plastic and fabric formwork are lightweight and easy to handle but are not as durable as steel, wood, or plywood.
A formwork system consists of several components, including panels, ties, and hardware. The panels are the most crucial component and are used to create the shape and size of the concrete. Ties are used to hold the panels together and provide support. The hardware includes clamps, brackets, and other components used to secure the formwork in place.
Formwork is an integral part of the construction process. It is designed to provide support and shape to wet concrete until it sets and becomes self-supporting. There are various types of formwork systems available, and each is designed to suit specific construction requirements. In this section, we will discuss the design and application of formwork systems.
When designing formwork, it is essential to consider the loads that the formwork system will be subjected to. The weight of the wet concrete, the weight of the formwork, and the weight of the workers and equipment must be taken into account. The formwork must be designed to withstand these loads without buckling or collapsing.
Different structural elements require different types of formwork systems. For example, columns require column formwork, beams require beam formwork, and slabs require slab formwork. The formwork system must be designed to provide adequate support and shape to the concrete until it sets.
Safety and stability are critical considerations when designing a formwork system. The formwork must be stable and secure to prevent collapse or any other form of failure. The formwork system must be designed to provide adequate support and shape to the concrete while ensuring the safety of workers.
To ensure safety and stability, the formwork system must be properly braced and anchored. The formwork must be designed to withstand the wind and other environmental factors that may cause it to collapse. The formwork system must also be designed to allow for easy access and egress for workers.
One of the most significant factors that affect the choice of formwork is the cost. The cost of formwork is influenced by various factors such as the type of material used, the design of the formwork, and the labor costs involved in its installation and removal.
Reusable formwork is cost-efficient as it can be used multiple times, reducing the total cost of the project. Permanent formwork can also be cost-effective in the long run as it eliminates the need for repeated formwork installation and removal.
Formwork has a significant impact on the environment due to the resources used in its construction and the waste generated during its installation and removal.
The use of reusable formwork reduces the amount of waste generated during construction, making it an environmentally friendly option. In addition, permanent formwork can reduce the environmental impact as it eliminates the need for repeated formwork installation and removal.
Recycling of formwork materials is also an essential aspect of sustainability. Materials such as timber and plywood can be recycled and reused, reducing the environmental impact of construction.
In conclusion, formwork is a crucial component in the construction industry as it provides the necessary support for concrete structures to take shape. The different types of formwork used in construction have their advantages and disadvantages, and the choice of formwork depends on the specific requirements of the project.
Timber formwork is one of the most commonly used formwork types due to its availability, strength, weight, and cost factor. Steel formwork is durable and can be used for a longer time, but it is more expensive than timber formwork. Plywood formwork is easy to handle and can be used for curved structures. Aluminium formwork is lightweight and can be reused for multiple projects. Plastic formwork is cost-effective and can be used for small projects. Fabric formwork is flexible and can be used for complex shapes, while tunnel formwork is suitable for repetitive structures.
It is important to choose the right formwork type for a project to ensure that the structure is strong, durable, and cost-effective. The use of formwork has a long history, and various formwork systems have been used in different projects. The design and selection of formwork system depend on the project requirements, budget, and timeline.
Overall, the proper selection and use of formwork can significantly reduce construction time and costs while ensuring the safety and quality of the structure.
For more information, please visit concrete slab formwork systems.