A flat roof isn’t perfectly flat, it’s built with a slight fall so rainwater drains off effectively rather than pooling. UK Building Regulations require a minimum finished fall of 1:80, and roofs are typically designed with a fall of 1:40 to allow for construction tolerances, meaning the roof still achieves proper drainage once built.
A flat roof is defined as any roof with a slope of 10 degrees or less from the horizontal. They’re often seen as a cheaper, quicker alternative to a pitched roof, and while that’s true upfront, lifespan varies hugely depending on the material used. Older felt roofing can last as little as 6 to 20 years, while a modern EPDM rubber system, like the Firestone RubberCover we install, is built to last far longer, with a 50-year life expectancy backed by a 20-year warranty.

Flat roofs generally need more maintenance than a pitched roof, particularly if the surface is regularly walked on, which can disturb or damage the covering over time. Drainage is historically the weak point of flat roofing, since water only has one direction to go, downwards, so standing water (ponding) can become a problem if the roof’s fall isn’t adequate.
The most common issues you may encounter are:

• Alligatoring — the clearest sign that a flat roof needs replacing. This happens when the roofing material loses its elasticity and starts to crack and bubble, much like the skin of an alligator, usually a sign of an ageing asphalt or felt covering reaching the end of its life.
• Leaks and moisture — the most common flat roof problem, but one that’s manageable if caught early. Because a flat roof only drains downwards, any moisture that gets in has nowhere else to go, which can quickly lead to mould and fungus if left unchecked.
• Pooling water — over time a flat roof can shift slightly, creating dips where water collects rather than draining away. Left unaddressed, pooling accelerates wear on the roof’s surface and shortens its overall lifespan.

A properly installed EPDM rubber roof, like the systems we fit at Storm Right, is far more resistant to these issues than older felt or asphalt coverings, thanks to its flexibility, seamless single-sheet application and long-term durability.