Flat Roofing in Royal Wootton Bassett

Most of the flat roofs being replaced in the town now are original pour-and-roll or single-layer felt from the extension boom of the seventies and eighties. That material had a realistic life of ten to fifteen years and many of them are on year forty, having been patched by successive owners.

The failure is almost always at a joint or an edge rather than in the middle. Felt laps open as the bitumen loses its plasticisers, water tracks under the sheet, and the chipboard deck below turns to porridge long before anything appears on the ceiling. By the time a stain shows inside, the deck usually needs replacing too — which is why an honest flat roof quote separates the covering from the deck rather than pretending the deck will be fine.

A flat roof is not flat. It should fall at a minimum of 1:80 after deflection, which in practice means designing to 1:40 so that the sag of the timber over time does not leave you with a level surface. Water that cannot run off sits, and standing water finds every weakness a covering has.

Ponding is the clearest sign a roof was built without thought. If puddles are still sitting on your extension roof forty-eight hours after rain, the falls are wrong, and re-covering it in a better material without correcting them simply buys a more expensive version of the same problem. Firring strips or a tapered insulation scheme fix it properly at the point of replacement.

Where a flat roof sits over living space — a kitchen extension, a dormer bedroom — the build-up matters as much as the covering. A warm roof puts rigid insulation above the deck and the waterproofing above that, keeping the entire structure at inside temperature so warm moist air never meets a cold surface. A cold roof, with insulation between the joists, needs ventilation above it, and the ventilation gap is precisely what gets blocked or omitted.

A significant share of the flat roof leaks we are called to over extensions in SN4 turn out not to be leaks at all. They are condensation forming inside a cold-roof build-up that was never adequately ventilated. Replacing the covering does nothing for that; converting to a warm roof does.

Deck condition is the unknown until the old covering is off. Quotes that include a deck allowance without having seen it are guessing in one direction or the other.