Underfloor Heating Photos

Underfloor heating on a structural concrete slab floor

Structural concrete slab floor construction showing underfloor heating pipes attached to reinforcing mesh. This technique is no longer used in domestic houses because the response time of the heating system is very sluggish in comparison to the slab plus screed technique. The main advantage of using a structural slab installation is that the concrete can be poured in one operation, in one visit. However, the thermal mass is much thicker than a screed, therefore the response to demands in changes in room temperature takes a lot longer to become evident, which is fine in large commercial buildings where the temperature is likely to remain constant all the time, but not suitable where frequent changes in temperature are required.

Rigid insulation boards are laid onto the consolidated hardcore or blinding, and the locations of wall partitions, fixtures and fittings, are marked on the insulation. Wire reinforcing mesh is then laid over the insulation, and the underfloor heating pipes are tied to the mesh using wire ties. This is particularly labour intensive and takes much longer to install than using the slab plus screed technique. The mesh is then propped up on 50mm blocks, the concrete is poured and the underfloor heating pipes end up in the middle of the concrete. The slab is structural so it needs to be thick enough to provide the strength of the floor, which is often 150mm. This much thermal mass means that the floor takes much longer to warm up, because you're heating the entire concrete slab. As a result, the efficiency of the heat source is reduced because it takes a greater amount of energy to get the slab up to temperature.

Structural concrete slab close-up

Structural concrete slab floor construction diagram

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