Flat roofs have a bad name because so many were done badly. Three layers of felt over damp chipboard was never going to last. Done properly, with a sound deck, a warm-roof build-up and a modern membrane, a flat roof is one of the most reliable roofs on the house.
GRP fibreglass
GRP is laid wet on site: resin and glass mat over a new OSB3 deck, with pre-formed trims at the edges and upstands, then a coloured topcoat. There are no joints and no seams, which is where every felt roof eventually fails. It is our usual choice for extensions, dormer tops, bay windows, porches and garages. Light grey is the standard finish; other colours are available.
Single-ply membrane
Single-ply is a factory-made sheet, hot-air welded at the laps and fixed to the deck. It is quick to lay on large or awkward roofs, it copes well with movement, and it comes in grey, anthracite and lead-grey finishes. We use it on bigger domestic roofs and on new-build and commercial work.
Warm-roof build-up
On any flat roof over a living space we build a warm roof: vapour control layer, rigid insulation board, new deck and then the waterproof layer. The roof structure stays on the warm side of the insulation, so there is no condensation in the timbers and the room below is noticeably warmer. We will advise on the insulation thickness building control expects.
Roof lanterns and rooflights
A flat roof is the ideal place for a roof lantern or a flat rooflight, and the right time to fit one is when the roof is being done. We build the kerbs and upstands into the roof, fit the unit and dress the waterproofing up and over, so the light and the roof are guaranteed together. See roof lanterns and Velux windows.
Flat roof repairs
If an existing GRP or single-ply roof has a localised problem we can usually repair it. Old felt roofs can sometimes be patched to buy time, but we will be honest when a repair is not worth paying for.