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The difference between formwork and falsework
The pouring of concrete, like many construction processes, has its own set of jargon. An often-asked question about poured in-situ concrete is, what is the difference between formwork and falsework? However, in some regions – such as the USA – falsework is referred to as shoring instead. Whilst it can be easy to confuse these terms, they both have a different role to play during the installation of a concrete structure.
What is concrete formwork?
Although the term “concrete buildings” conjures images of blocky and stark structures, concrete is an adaptable material that can be moulded into almost any form. As concrete is semi-liquid when it is poured, it needs to be moulded and contained in the desired shape until the concrete cures and becomes hard – this is the job of the formwork.
Formwork – or concrete forms – are often panels that can be attached together to form a mould in the desired location on site. The inside face of the formwork that will be in contact with the concrete is smooth to create a flat surface once the concrete has cured. The outer side is made up of a frame that the inner surface is attached to, which provides structural integrity and strength as well as a way to carry panels and join them together.
Formwork is not just limited to square or rectangular panels, however. For a circular mould, curved panels can be joined together to create a specific radius. In some cases, special formwork is created for unique or unusual shapes – such as the organic and free-flowing curves of some of Zaha Hadid Architects’ concrete buildings, or the parabolic arches of Felix Candela’s famous Los Manantiales restaurant in Mexico City.
So how does it work?
To create a poured in-situ concrete wall, two formwork panels are placed with the smooth interior facing each other. The distance between them will be the specified depth of the wall. Opposite panels are held in place using tie rods, which are steel rods that pass through the panel and hold the panels in place to create the mould.
After the concrete has cured, the tie rods are removed. Adjacent formwork panels are joined together with clamps, such as the innovative MEVA assembly lock, which provides a structurally continuous connection between the panels. To cope with the pressure that is exerted by the wet concrete, horizontal supports or shoring systems may be needed to stop the vertical panels from tipping over.
How sustainable is plastic-faced formwork?
Plastic-faced formwork includes a smooth polypropylene face that is attached to a steel frame. It is one of the most commonly used types of formwork, next to plywood. It offers better longevity, but is still a petroleum-derived plastic.
In terms of advantages, plastic facing is both durable and sustainable. Not only do the panels last longer than plywood, but they can also be easily repaired without affecting the performance should they get scratched or perforated – unlike plywood, which has a finite lifespan. For example, our alkus® all-plastic facing can be used up to 1,500 times – a considerable increase in comparison to plywood and up to six times more than many other plastic panels. Not having to continually re-order and replace formwork by being able to re-use or repair existing stock saves time and money, as well as raw materials. This increased longevity is a significant contributor to sustainability efforts.
Is plastic formwork easy to install?
A common concern is whether plastic formwork can be installed as easily as wooden formwork, which provides a high degree of flexibility. However, plastic formwork is just as adaptable. Just like plywood, plastic-faced formwork can be nailed and screwed together, and then repaired if needed for the next application. Cleaning the panels for re-use is simple – they can withstand high-pressure washing of up to 1000 bar (14,000psi), and because they are impervious to moisture, they will not warp or rot whilst in storage.
That said, there is a drive to reduce the amount of plastic we use, as plastics take a long time to biodegrade, can create microplastics which harm wildlife, and are derived from unsustainable sources such as crude oil and natural gas. In addition, there is also a low recycling rate of plastic in some countries, and plastic pollution and litter can be a further problem.
The polypropylene that is used in plastic-faced formwork, such as our alkus® all-plastic facing, is easy to repair and recycle without releasing any toxic chemicals during the recycling process. Polypropylene also consumes the least amount of energy during production, therefore producing the lowest carbon dioxide emissions when compared to other plastics. Our alkus® panels are also fully polypropylene with a smooth polypropylene face and polypropylene foam core, unlike other products which are simply plywood sheets with a plastic facing.
What is falsework or ‘shoring’?
Falsework – or shoring, in some regions – is a temporary structure that is used to support formwork in a horizontal position, using elements such as props and scaffolding. The concrete is then cast onto the formwork, and the falsework holds the formwork in place until the concrete has cured – for example, if casting a floor slab for a second storey building. In this case, the falsework would support formwork panels so the slab can be cast above ground. Another use for falsework would be to support the formwork for concrete arches or other unusual shapes.
However, falsework generally uses vertical elements, unlike the supports or shoring systems that are used to provide horizontal support to formwork panels. These are not falsework; instead, they are designed to help the formwork panels cope with the pressure that is exerted by the wet concrete until it cures.
Why are formwork and falsework important?
Besides providing a mould for wet concrete, good quality formwork and falsework systems help keep site staff safe and contribute to the quality of the concrete finish. Formwork and falsework that is heavy or difficult to install increases the risk of manual handling injuries, as well as increasing the time required for installation. Even more importantly, if a formwork or falsework system collapses because it cannot handle the concrete pressure, site staff will be put at risk of serious injury.
Hence, it is vitally important to choose the right system for the loads that will be applied during service. The type of concrete used, the temperature and rate of the pour, as well as the volume being poured are all contributing factors when determining the concrete pressure and selecting an appropriate system.
The formwork chosen will also affect the final appearance of the concrete. For some applications, such as where the concrete will be covered by cladding, this may not be an important consideration. However, if the concrete will be on show, often a smooth, seamless finish is desired. Poured in-situ concrete is expensive to repair and replace, so achieving the specified finish the first time is preferable to spending time and money rectifying a surface that is marred from poor formwork.
Choosing the right solution
Formwork and falsework (or shoring) work together to provide a safe method of installing concrete in-situ yet are two distinct elements. MEVA has a wide range of high-quality formwork products for every application and can help advise regarding any requirements for falsework.