This technique is used when it is necessary to install the pipes before the structure of the building goes up, e.g., if access later would make pouring concrete difficult. Insulation should be a minimum of 75mm flooring grade rigid insulation, or to satisfy building regulations. The underfloor heating pipes are attached to the reinforcing mesh using wire ties. The mesh is then propped up on 50mm blocks and the concrete is poured in one operation with the pipes suspended midway. Since the concrete forms a structural slab the thickness should be 150mm (subject to local planning regulations). Response from the underfloor heating pipes is slower than with the screed method, but because the thermal mass is greater it will hold more heat energy for longer.

Photo - Structural concrete slab with underfloor heating pipes installed

Close-up Photo - Structural concrete slab with underfloor heating pipes installed

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