When building concrete walls for buildings or other structures, it is important to first create a stable mold in which the concrete can be poured and held in position as it sets. Such a mold is usually created using wall formwork, which includes straight, flat panels that are held together with couplers, bars, and braces known as falsework. The wall formwork may be temporary or permanent, depending on the design of the structure and the type of forms being used. Common materials for formwork include certain types of plywood, steel, and even plastic.
Before any concrete is poured, wall formwork carpenters will enter a job site to erect the temporary mold structures. This process usually involves reading a blueprint and placing the forms in the appropriate places, then securing the forms to each other so no gaps exist and no excess play is present. The wall formwork structure can be exceptionally simple if the wall is straight, or it may be more complex if the wall features turns, curves, or angles. Formwork carpenters are usually specially trained to know how to set these forms in place, which types of forms to use, and which falsework components are most appropriate.
For smaller walls, plywood wall formwork is likely to be used because this type of plywood is generally inexpensive, lightweight, easy to use, easy to store and transport, and reusable. A specific type of plywood must be used; other types may be susceptible to water damage such as warping, splitting, or cracking, making them inappropriate choices for formwork. All sizes of projects, except for very large ones, may benefit from plastic forms, which are also lightweight and easy to transport, but more susceptible to cracking and warping. In some cases, plastic molds are permanent and will be left installed as part of the permanent structure.
Steel wall formwork is usually reserved for larger projects and projects that require exceptionally straight and flat walls. Steel will not bend or warp, and it will provide the flattest surface, but these forms can be expensive, not to mention difficult to transport and store. Installing steel wall formwork generally takes more effort and may require the use of heavy machinery such as forklifts, telehandlers, or even excavators, since the panels are very heavy and may need to be lifted high off the ground. Most professional construction companies prefer to use steel formwork because of its reliability.