12/06/2026
Mythbusting ✅
Flat roofs used to have a bad reputation.
Years ago they were often finished with layered felt systems, which could deteriorate over time, particularly where joints failed or installation was not perfect. This is where the old stereotype of “flat roofs always leaking” and ""water pooling"" really used to come from.
Modern flat roof construction is very different.
Today, many extensions use GRP fibreglass roofing. This creates a seamless, fully bonded waterproof layer with no exposed joints where water can work its way in. The result is a tough, durable surface that performs far better than older felt systems and requires very little maintenance.
That is one of the reasons flat roofs have become such a popular feature in modern extensions. They allow for clean architectural lines, generous ceiling heights and features like rooflights or glazed lanterns, while still providing a reliable roofing solution.
So if you are considering a flat roof as part of your design, rest assured that modern systems have moved well beyond the problems of the past.