Design and specification of watertight flat roofs

Designing and constructing flat roofs to be watertight depends on good workmanship, careful detailing of the waterproofing membrane, and achieving the correct drainage falls.

Should a leak occur in the roof covering due to damage or poor installation, water can enter the roof build-up. It passes through and along the layers of the construction, potentially tracking a long way from the leak and causing widespread damage. If water is seen inside the building, the location often does not correspond with the location of the leak, making it hard to find where water has entered the building.

Specifying FOAMGLAS® insulation provides a flat roof with a watertight insulation layer. The water cannot track through the roof construction away from the leak, and the insulation does not become sodden. FOAMGLAS® cellular glass remains watertight for the life of the building, and a further benefit is that a separate vapour control layer (VCL) is not required.

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