Flat roofs have a reputation — and unfortunately, it's often deserved. Built badly, a flat roof will leak within a decade. But built correctly, modern flat roofing systems are durable, energy-efficient and capable of lasting half a century. The difference lies entirely in specification and workmanship.
Here we explore the most common flat roof problems we encounter across South West London, and the modern solutions that resolve them permanently.
Pooling water. The most prevalent flat-roof fault. Water should never stand on a flat roof for more than 48 hours after rain. Pooling indicates incorrect falls (the gradient that sheds water) or blocked outlets. The solution is to re-deck with engineered falls or install tapered insulation boards, and ensure outlets are correctly sized and located.
Blistering and bubbling felt. Blisters form when moisture or air is trapped beneath felt during installation, then expands in sunlight. A blistered felt roof has a limited remaining life and will eventually split. Modern EPDM and GRP systems are seamless and immune to blistering, making them the recommended replacement.
Failed seams and joints. Traditional felt roofs rely on lapped joints that degrade over time. Every joint is a potential leak. EPDM rubber and GRP fibreglass roofs can be installed in a single seamless membrane, eliminating joints entirely.
Inadequate upstands. Where a flat roof meets a wall or parapet, the membrane must turn up by at least 150mm to prevent water running back under. Many older flat roofs have inadequate upstands — a common and easily missed leak source.
No insulation. Cold flat roofs suffer condensation that rots the deck and timbers. Converting to a warm-roof specification, with insulation above the deck, dramatically improves thermal performance and eliminates condensation.
If your flat roof is showing any of these signs, it may be time to consider replacement rather than repeated repairs. A modern EPDM or GRP system, correctly installed with proper falls and detailing, will protect your home for 30–50 years.
Contact Stay Dry Roofing for a free flat-roof assessment and a fixed quotation for a system engineered to perform.