Can a Flat Roof Be Repaired Without Replacement?

Built-Up Felt

Layers of bitumen felt bonded together, usually three, and still the commonest covering on older extensions and outriggers across Birkenhead.

Repairable: a local split or tear; a lifted or failed edge detail; an upstand that has come away from a wall; a blister that has not burst; a failed joint at an outlet. All of those are patched with matching material, properly bonded and dressed, on a covering that still has flexibility in it.

Not repairable: widespread crazing where the surface has gone brittle and cracks when pressed; multiple existing patches; the top layer having weathered off across the area so the mineral finish is gone. At that stage the material has lost the plasticiser that made it flexible and it will crack next to wherever you patch it.

EPDM Rubber

A single sheet, so there are very few joints in the field of the roof.

Repairable: punctures and tears, which patch well with the same material and the correct primer and tape. Seam failures at a lap or a detail. Failed bonding at an upstand or a corner. Because EPDM stays flexible for a long time, these repairs generally take properly.

Not repairable: a sheet that has been repeatedly punctured, or one that has gone chalky and hard over a large area. And EPDM laid over a deck that moves will keep failing at the same point, which is a deck problem rather than a covering one.

GRP Fibreglass

Rigid, laid in situ, and it fails where things move.

Repairable: a crack, ground back and laminated over with matching material; a damaged edge trim; delamination at an isolated point.

Not repairable in the useful sense: cracks that keep reappearing along the same line. GRP is rigid and the deck below it is not; if the deck deflects at a joint, the laminate cracks there and will do it again after any repair. That needs the deck stiffening, which is a bigger job than the roof.

Widespread crazing across the surface is age and ultraviolet exposure, and it is terminal.

Single-Ply and Mastic Asphalt

Single-ply membranes are welded at their seams and are readily repairable by somebody with the right welding kit for that system - which is worth checking, because the systems are not interchangeable.

Mastic asphalt, found on some older and better-built flat roofs, is repaired by heating and reworking the material itself. It is a specialist trade and genuinely repairable, often for decades longer than people assume. Its usual failures are cracking at upstands and crazing at the surface, both of which can be dealt with.

What Is Repairable on Every Type

The four places flat roofs actually leak are all details rather than covering, and all four are repairable on almost any system with life left in it.

The upstand where the roof meets a wall - carried up high enough, tucked in or capped properly.

The edge trim or drip at the perimeter.

The outlet - clearing, or renewing the detail around it.

Penetrations - a soil vent, a flue, a rooflight kerb.

If your leak is at one of those, the answer is very likely yes regardless of what the covering is made of.

Birkenhead: Settle Who Instructs First

On a converted house, the flat roof over a back addition is frequently a shared or freeholder responsibility even where it is only reachable from one flat - and even where only one flat suffers when it leaks.

Check the lease rather than assuming. A leaseholder instructing repairs directly on a structure that is the freeholder's to maintain can create a bill nobody else agreed to, and can complicate recovering it through the service charge.

If you rent, the roof is your landlord's responsibility under section 11 of the Landlord and Tenant Act 1985. Report it in writing and keep a copy.

What we can do in either case is come and produce a written assessment naming the covering, the defect and its location, separately from any work. On a managed building that is frequently the most useful thing anybody can hand over, because it turns an argument into a decision.