Types of flat roofs

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The three most popular flat roof coverings are: EPDM rubber, torch-on felt and GRP.

EPDM is a continuous sheet of special rubber membrane especially formulated to withstand harsh weather conditions: bright sunlight, freezing, snow and rain. It is bonded to the roof surface by a rubber adhesive compound. EPDM has been around for many years now and is proving a robust and reliable roof covering.

Torch on felts have now replaced the old style poured hot bitumen. Typically these felts are applied in a two or three layer process where the joints are staggered. The base layer is a waterproof yet vapour permeable layer and the top surface layer incorporates mineral to improve long term weathering.

GRP stands for Glass Reinforced Polyester. Mats of woven glass strands are impregnated with polyester resin which is poured and rollered into the mat. Polyester is a two-part mixture of resin and catalyst. When mixed together the resin hardens to form an extremenly durable cross linked composite layer. Costing a little more than the other two options GRP is usually reserved for roofs with protruding service ducts, upstands and steps. This is because GRP can be draped and contoured when wet into complex shapes that are then completely waterproof when set.