Formwork and Falsework
Definition of Falsework and Formwork
What is Falsework?
Falsework is a temporary support structure used to support elements of a building during construction. This will commonly be a framework of props beams and bracing to support concrete formwork.
What is Formwork?
Formwork is a temporary surface or mould to contain and support fresh concrete while it sets and hardens. It is commonly made from timber plywood sheeting or steel pans to form flat surfaces. Specialist suppliers can make many unusual shapes with polystyrene, fiberglass, steel, and timber. Falsework is to support formwork required at height.
Falsework and formwork are combined to make an engineered mould for wet concrete. It is essential that a qualified, experienced engineer calculates the pressures of the wet concrete and calculates a design that will withstand the pressures without movement. A steel reinforcement cage is installed behind the formwork to make reinforced concrete.
Falsework and formwork for basements
Falsework and formwork is required for all basements and underpinning made from concrete. Basement excavations will be formed by the groundworks contractor and supported by an engineered system of earthwork support. This system remains in place until the groundworks contractor completes the permanent basement structure.
Once the concrete basement slab is poured, the groundworks contractor will build a falsework and formwork system for the walls. The groundworks contractor must have an independent design to make sure it can carry loads of the wet concrete. The concrete must be checked for temperature and poured at an agreed flow rate to ensure the formwork is not overloaded. The rate could be 1.2m height per hour. Wall formwork is kept in place until cube crush testing of samples has shown sufficient design strength.
An Engineer will design a falsework and formwork system for the suspended soffit slab. The Groundworks Contractor will build the system exactly like the design to take the load of the wet concrete and the people and plant pouring the concrete. An allowance was made for the weight of some build-up of concrete during the pouring process.
Wall formwork for Basements
Wall formwork for basements is constructed in many different materials and systems. Timber plywood is fixed to a timber falsework system, but it is more common for groundwork contractors to use a proprietary system supplied with a design and drawings. Steel panels with bolted connections to steel soldier props and struts is a quick and reliable system.
Steel panels are made in many standard sizes and can be small enough to lift by hand and bolt together. Larger panels can be up to 3m square and lifted by a crane to speed the process up. Steel soldiers and props will make a falsework system is bolted to the formwork as per the design. Struts will be bolted to the concrete basement slab to support the loads and prevent movement.
The groundworks contractor will thoroughly check the system and then pour the concrete to an agreed height per hour specified by the design Engineer. Once the concrete is set and hardened to an agreed strength, the falsework and formwork is removed to expose the finished basement walls.
Soffit slab formwork and falsework.
A soffit slab is a common name for a suspended concrete slab formed by pouring wet concrete onto a formwork and falsework system. A soffit is the underside of an architectural or structural component. A groundworks contractor will commonly construct a soffit slab formwork from plywood built onto a system of structural timbers to form a grid.
Below the soffit slab formwork will be a falsework designed to take the weight of the wet concrete, reinforcement, and construction team. There are many proprietary systems for a soffit slab formwork. The best systems are steel tripod props or steel framing systems because they are quick and easy to install.
Once the new concrete slab has cured long enough to meet the required strength, the falsework and formwork is removed. Concrete cube testing by an independent company will show that strength is gained.