Flat Roofing in Plymouth

Standing water, or ponding, happens when the roof structure lacks the necessary 1:80 fall, usually because timber firrings were cut too shallow or have sagged over time. While modern waterproof membranes handle moisture well, prolonged standing water collects dirt, encourages moss growth, and accelerates surface wear during freezing winter spells. When we strip an old flat roof, we fix treated timber firrings directly across the existing joists to establish a continuous slope that sends rainwater straight into the gutter.

Both materials handle coastal gales and driving salt rain well, but the right choice depends on the size and shape of your roof. GRP fibreglass cures into a completely seamless, rigid shell finished with a marine-grade topcoat, making it virtually impossible for high winds to lift around parapet walls and complex roof corners. EPDM rubber is better suited to larger, unobstructed spans like double garages because it stays naturally flexible as the building moves and can be installed in continuous sheets without joint seams.

If the existing deck is made from old chipboard, plywood, or sagging floorboards that have absorbed damp from historic leaks, it must be removed. Laying a new membrane over soft or swollen timber leads to blistered seals, spongy spots underfoot, and early failure. We inspect the structure once stripped and fix 18mm tongue-and-groove OSB3 structural boards to the rafters to give the new rubber or fibreglass a solid, bone-dry base.

Water tracks the easiest physical path once it breaches the outer skin, which is rarely straight down into the room below. Rain gets past a failed seam or split upstand, hits the underlying timber deck or insulation, and flows along the top or bottom of a joist before finding a drywall screw or plasterboard joint to drip through. Finding the true source means checking the perimeter flashings, wall abutments, and deck falls above the ceiling rather than just patching directly over the damp patch.

Modern elastomeric torch-on felt is a durable, heavy-duty system that performs far better than the old pour-and-roll bitumen used decades ago. It consists of a nailed vent layer, a reinforced underlay, and a thick polyester cap sheet with a slate mineral finish melted into position with a gas torch. It remains one of the most reliable and hard-wearing options for basic garage roofs, workshops, and outbuildings where puncture resistance is essential and material costs need to stay sensible.