Formwork in construction is a key part of the building process. It helps shape concrete into structures that can be removed and reused after the project is complete. It can be created from a number of different materials, and the way it is erected depends on the project’s needs.
The most common formwork material is timber. This is used to create a framework for concrete sections and is inexpensive, flexible, and reusable. However, it is susceptible to termites and can easily warp or swell.
Another popular formwork material is steel. It is lightweight and can resist more fresh concrete pressure than plastic or wooden formwork. It is also more durable and can be re-used more than 100 times.
Aluminum formwork is also a common option. It is light, crane-independent and less expensive than steel formwork. It is re-usable and can be fixed and removed without trouble.
Plywood forms are also commonly used to make concrete forms. They are generally cheaper than steel or aluminum, but they have a shorter lifespan and are rarely re-usable.
Formwork can be assembled by hand or prefabricated in a factory. It may arrive in a stack of panels with hardware like ties, wedges, clamps, braces and brackets that can be bolted together or screwed to the frame. On some projects, the architect-engineer and concrete contractor will collaborate to determine the best method for assembling and using the formwork.
Insulating Formwork
This type of formwork is constructed on-site and remains in place after the concrete is poured. It can offer a number of benefits, including superior thermal and acoustic insulation, space for utilities and an integrated furring strip to allow cladding finishes to be applied over it.
Plastic formwork is a light weighted and interlocking system that can be used more than 100 times. It can be adapted to suit large concrete sections and is particularly economical for lost-cost, repetitive constructions such as mass housing schemes.
Typical examples of plastic formwork include column formwork, beam formwork and slab formwork. It is important to ensure that the structure is strong enough for its intended use, and the formwork system is designed properly.
Beam and Slab Formwork
For beams, conventional formwork is made up of joists, stringers and boards. Each section of the beam is supported on one or two joists, depending on its size. Beams are usually supported at both ends and the middle, to keep them straight. Beam forms can be angled to reduce the deflection of the beam and prevent buckling.
In contrast, slab forms are typically made up of a single slab, which is anchored to the joists by a series of wedges. This keeps the slab from buckling, but it can be a challenge to maintain a stable structure when the slab is rolled or pressed into place.
Other types of formwork include the traditional wall formwork system, which is constructed with a series of sleeved formwork ties. The ties are usually placed on both sides of the wall and take up most of the fresh concrete pressure. Push-pull props or heavy-duty braces are sometimes also attached to the formwork system for stability during operation.
