# What is a formwork slab floor?
**A formwork slab floor is a type of concrete floor system in which prefabricated formwork panels or plates serve as both the mould for pouring concrete and, in many cases, a permanent structural component of the finished floor. Unlike traditional formwork that is stripped after the concrete cures, the formwork in this system typically remains in place, acting as the ceiling finish of the storey below or as part of the structural cross-section of the slab.**
## Application
Formwork slab floors are widely used in residential and commercial construction because they combine speed of installation with structural performance. The system works by placing prefabricated panels — usually made of prestressed concrete, fibre cement, or steel — across the supporting beams or walls. Reinforcement is then placed on top, and a layer of structural concrete (the topping) is poured over the panels.
Common types of formwork slab floors include:
– **Precast concrete plank floors** — thin, prestressed concrete planks span between supports. After placing the planks, a reinforced concrete topping is poured on-site. The planks remain in place permanently as the bottom of the slab.
– **Steel deck composite floors** — profiled steel sheets act as formwork and, once the concrete cures, as tensile reinforcement. This system is very popular in steel-framed buildings.
– **Fibre cement board floors** — lightweight boards used as permanent shuttering in smaller residential projects.
– **Expanded polystyrene (EPS) formwork floors** — lightweight EPS blocks placed between concrete ribs, reducing dead weight while maintaining structural capacity.
The advantages of formwork slab floors include reduced labour and construction time, since there is no need to strip formwork after the pour. They also provide a flat, finished soffit (underside) that requires minimal plastering. Additionally, the prefabricated elements ensure consistent quality and reduce on-site waste.
When designing a formwork slab floor, engineers must consider the span, the imposed loads, the thickness of the concrete topping, and the reinforcement requirements to meet structural and fire safety standards.
## Related terms
– Concrete slab
– Formwork
– Prestressed concrete
– Composite floor
– Reinforcement
– Dead load
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