Seamless GRP Fibreglass Flat Roof on Kitchen Extension

The existing torch-on felt flat roof over a 42m² open-plan kitchen extension had developed deep blisters and cracked perimeter seams after 12 years. Rainwater ponded heavily in the centre, creating visible water stains on the recessed ceiling spotlights inside.

The original deck had zero fall (slope) and insufficient thermal insulation, creating heavy condensation during winter. The chipboard decking was moisture-damaged and needed full replacement, though the primary timber joists remained sound.

We stripped the failed felt and wet decking. We installed new treated timber firring strips to establish a correct 1:40 drainage fall towards the gutter. We laid 120mm foil-faced rigid PIR warm-roof insulation boards, covered with 18mm tongue-and-groove OSB3 decking. Two layers of high-tensile glass matting and Lloyd's-approved polyester resin were applied, finished with a hard-wearing Dark Slate Grey UV-stable topcoat and preformed drip trims.