Leaking Flat Roof Repair in Canterbury

Why Flat Roofs Leak

Most leaking flat roofs in Canterbury are covered in built-up felt, and they leak because felt has a short life. Over 15 to 20 years, sun, frost and movement make felt brittle; it cracks, it blisters where trapped moisture expands, and its seams — always the weak point — open up. Once any of these lets water through, it soaks into the timber deck beneath and finds its way inside.

The other classic failure point is the detailing rather than the field of the roof. The upstand where a flat roof meets the house wall, the junction around a parapet, and the outlet where water should drain are where felt roofs most often fail first. Water also pools where a roof was laid without adequate falls — a flat roof should never be truly flat, and standing water accelerates every kind of failure.

BS 6229, the British Standard for flat roofing, requires adequate falls so water drains to the outlet rather than ponding — inadequate falls are a leading cause of recurring flat-roof failure.

Source: BS 6229 (flat roofs with continuously supported flexible coverings)

How a Flat Roof Leak Is Repaired

A genuine flat-roof repair starts by finding where water is getting in, which on a flat roof is easier said than done because water spreads across the deck before it drips through. Once the failure is located — a split, a blistered seam, a failed upstand — a localised repair patches or re-dresses that area with compatible materials.

Honest assessment matters here more than on most roofs. A small, isolated failure on an otherwise sound modern flat roof is worth patching. But patching one crack on a felt roof that's brittle all over just buys a few months before the next failure somewhere else — the classic false economy. A good roofer tells you which situation you're in rather than selling you a cheap patch that fails by winter.

We survey Canterbury flat roofs free, find the actual source, and tell you plainly whether a repair makes sense or whether the roof has reached the point where recovering it is the better value decision.

Repair or Replace? When Each Makes Sense

The repair-or-replace decision comes down to the age and overall condition of the covering. If a modern GRP or EPDM roof has a single, localised failure — a damaged trim, an isolated puncture — repair it. If a felt roof is under about ten years old and has failed at one clear point, a repair is reasonable.

But if the felt is 15 years or older, brittle across the whole surface, blistered in multiple places, or ponding badly, replacement is the sensible call. Recovering it in a modern system — GRP fibreglass or EPDM rubber — more than doubles the lifespan to 25–35 years for a modest increase over repeated repairs. We don't refit felt as a replacement, because replacing felt with felt just restarts the same short clock.

In Canterbury, flat roofs are overwhelmingly on rear extensions, garages and dormer conversions rather than main roofs. The Victorian and Edwardian terraces around St Dunstan's and Wincheap have decades-old rear kitchen and bathroom extensions whose original felt is well past its life — these are the recover jobs. The 1930s and post-war estates have garage roofs that suit cost-effective EPDM.

Getting It Right the Second Time

If your flat roof has leaked repeatedly despite repairs, the problem is usually one of two things: the falls are wrong so water ponds, or it's been patched instead of properly recovered. Both are fixable, but they mean addressing the whole roof rather than the latest crack.

A recovered flat roof, laid with proper falls to the outlet and finished in GRP or EPDM, carries a substantial guarantee and should be trouble-free for decades. If you're on your third patch, that's the signal to stop patching and recover it once, properly.