What is a composite floor?
What is a composite floor?
A composite floor is a type of floor built from materials of different kinds so that it is both light and strong. Unlike conventional solid-slab floors, which are made solely of concrete poured into formwork, composite floors are thinner because a large share of the floor load is carried by the structure beneath the reinforced concrete. Concrete is very strong and withstands extreme compressive forces, but it is less resistant to tensile forces. The underside of solid concrete slabs is regularly subjected to such forces, leading to tiny cracks in the structure.
To overcome this problem, other materials capable of resisting the tensile forces generated by the floor load would have to be combined with the concrete. For composite floors, steel plates, steel joists or timber structures are used so that the installation is both strong and light. Materials such as timber or steel withstand high tensile forces, which makes them well suited to the lower parts of composite floors.
Why choose composite floors?
Composite floors are easy to install and suit any type of setting (attic, upper floor, mezzanine, etc.), whether in new builds or renovation projects. The installation is also less expensive and, above all, does not require a large-scale building site.
Whether timber-concrete or steel-concrete composite floors, they are an excellent choice for reducing the load on load-bearing walls, thanks to the lightness of the structure relative to the load it can carry.
How is a timber-concrete composite floor installed?
Installing a timber-concrete composite floor is relatively simple. The structure rests on joists and transverse beams that bear firmly on the building's load-bearing masonry (concrete piers, load-bearing walls, etc.). To improve the acoustic quality of the concrete, and above all to give the floor more rigidity, permanent formwork made of OSB panels or plywood can be added. Make sure that anchor studs of a suitable size are correctly installed so that the concrete is firmly fixed to the underlying structure. In this way, tensile and compressive loads will be perfectly distributed between the concrete and the timber, so you get the full benefit of composite floors.
How are steel-concrete composite floors installed?
Besides timber, steel is also an extremely strong material that withstands heavy tensile forces. Some composite floors therefore take advantage of the properties of this metal to be robust while remaining light. In addition, steel, being a metal alloy, allows the floor to carry more load, which is particularly suitable for warehouses and storage areas.
There are currently two ways of combining steel structures with the concrete layer.
– floors on steel beams
– floors on steel decking
Composite concrete floor on steel beams
In this type of installation, the floor structure rests entirely on a set of steel beams (mainly IPE or HEA beams). The characteristic shapes of these steel beams (I or H) give the structure its strength and robustness, which is ideal for building steel-concrete composite floors. Once the joists, reinforcement and anchor studs are correctly in place, the concrete slab can finally be poured. Depending on the load carried by the floor and the required span, the concrete layer can vary from 10 to 30 cm in thickness.
Composite concrete floor on steel decking
Another type of steel-concrete composite floor is the floor on steel decking. The tensile forces carried by the floor are transmitted to the steel decking attached to the underside of the concrete. The corrugated metal sheets also act as permanent formwork when the slab is cast. With a thickness of between 0.5 and 1 mm, steel decking is not only light and easy to handle but also gives the installation outstanding strength and robustness. These materials are also inexpensive, durable, and easy to cut and handle, which makes steel-decking floors increasingly popular with DIYers.
For the reinforcement, the principle is the same as for solid-slab floors. Make sure in particular that the wire meshes overlap properly and are tied (or possibly welded) together. While the poured concrete is drying, safety standards require a supporting prop to be added every two metres. The structure should only be put into service after 3 to 5 weeks of drying.
Finishing the underside and installing the ceiling
Once the concrete has fully set during these few weeks of drying, it may be time to move on to finishing the underside. This is the visible face of the lower part of the floor, so it is an excellent way to personalise the room. Suspended ceilings can be installed beneath these composite floors to hide the joists and the steel decking that support the concrete.
As with ceilings beneath conventional floors, ventilation ducts and various electrical conduits can be discreetly concealed there. Insulating materials such as glass wool can also be added to the installation to improve the thermal and sound insulation of the floor.
We are here to help. If you have any questions, do not hesitate to contact us.