Formwork is an essential component to any type of concrete construction. Formwork refers to temporary or permanent moulds into which concrete is poured that subsequently hardens. Formwork has been used for thousands of years in the construction industry, with one of the earliest examples being the Pantheon in Rome which was built around 120AD.
Since concrete is relatively strong in resisting compressive loads, but has poor tensile strength, most of the earliest concrete structures using formwork consisted of arches, domes, and vaults. The earliest types of formwork were widely used in masonry since concrete was very complex and subsequently had a limited production capacity. It wasn’t until the mid-19th century when concrete became the favoured choice of building materials in construction.
Types of formwork
There are various types of formwork used depending on the formwork material and the type of structural element being built. For example, slab formwork is used to build concrete slabs, column formwork is used to build concrete columns and so forth.
When suspended concrete slabs are constructed that are not directly supported by the ground, slab formwork is required. Slab formwork includes formwork panels, stringers, joists, shores, and other supporting materials that enables the concrete to be poured and set above the ground. There are a variety of materials used in slab formwork, including plywood, timber, metal, aluminium, and sometimes even plastic components that are used to shape and give strength to the concrete.
What is slab formwork?
Slab formwork essentially supports the weight of the concrete during the curing process and when the concrete slab is positioned on permanent supports. Bases (also known as sills) are required that are made from wood or metal and these bases support the vertical stringers which in turn support the horizontal joists. The horizontal joists create a flat surface where timber, plywood, steel sheets, aluminium or fibreglass can be used as a base onto which the concrete is poured.
In most cases, formwork can be re-used and the method of removing the formwork once the concrete has been set is known as stripping. After the formwork has been stripped, it must be cleaned to ensure the faces of the panels remain straight and there is no built-up of concrete. Reusable forms are known as ‘panel forms’ while non-usable forms are known as ‘stationary forms’.
Formwork jobs – Big and small
For smaller jobs, timber or plywood formwork is most common, however these types of formwork can warp, swell, or shrink, even with the application of water impermeable laminate. Consequently, timber and plywood formwork both have a short lifespan. On the other hand, steel sheets are used for bigger jobs where the formwork needs to be re-used many times. While more expensive to manufacture, steel sheets have a much longer lifespan than timber or plywood, however other materials such as fibreglass and aluminium are used in cast-in-situ construction where concrete slabs needs to have a curved surface.
Customisable formwork for many projects
Not only is slab formwork used to create horizontal and curved surfaces, it can also be used to create diagonal and vertical concrete structures. Today, formwork is highly modular and customisable which allows architects to create an almost endless number of concrete shapes and designs. The falsework, which are the components that secures the forms in place, also add to the modular nature of formwork.
Due to the large number of slab formworks available, it’s important that the most suitable and economical type of slab formwork is used depending on the project’s budget and specifications. Getting the right advice is paramount considering that small miscalculations in formwork requirements can lead to very costly errors.
If you’re in need of any slab formwork for your next project, or simply need some general formwork advice, get in touch with Uni-Span on 1300 882 825, or visit our website for further information: https://uni-span.com.au/formwork/