Flat roofs on extensions, garages and outbuildings need the right material and a proper finish to last. We install and repair felt and EPDM rubber flat roofs across Ely and the surrounding fenland villages.
When a flat roof starts letting water in, the first question is always the same: do we patch it, or does it all come off? The honest answer is that it depends on the age of the roof, the condition of the deck beneath it, and how widespread the damage is. Getting that call wrong costs money. Replace a roof that could have been repaired, and you spend more than necessary. Repair a roof that should be replaced, and you will be back to the same problem within a couple of years.
We install and repair flat roofs across Ely and the surrounding area, including Waterbeach. The guidance below is intended to help you understand what a contractor should be looking at before giving you a recommendation.
A targeted repair is the right answer when the bulk of the existing membrane is still sound and the damage is localised. A blister in the felt, a lifted seam, a crack at a flashing junction, or a small split caused by foot traffic are all examples of problems that can be fixed without stripping the whole roof.
For a repair to hold, the deck beneath must be dry and solid. If a contractor lifts the damaged section and finds the timber is wet or soft, a patch will not give you a lasting result. The moisture has to be dealt with first, which often means the work grows beyond the original patch.
A repair also makes sense economically when the roof is relatively young. A felt system that is under ten years old and has failed at one specific point, perhaps a flashing that was not dressed correctly when the roof was built, can reasonably be patched rather than replaced. The rest of the membrane still has life in it.
Small repairs on flat roofs typically cost between £150 and £500 depending on the size of the affected area and the complexity of the flashing work involved. These are general UK figures and individual jobs vary.
Replacement makes sense when the membrane is old and failing across its full area, not just at one point. Felt that is extensively cracked, blistered throughout, or pulling away from the upstands at multiple points is telling you that the whole system has reached the end of its life. Patching individual failures on a roof in that condition is a short-term measure at best.
A critical factor is the condition of the deck. When old felt is stripped back and the timber decking beneath is wet, soft or rotten in several places, the roof must come apart anyway to replace those boards. At that point, the labour for a full replacement is not much more than the labour for a patch, and you get a new system rather than new felt over a questionable base.
Another trigger for replacement is repeated leaks. If a flat roof has been repaired two or three times in recent years and the leaks keep returning, the membrane as a whole has lost its integrity. Continuing to patch is paying good money for a temporary fix.
Full flat roof replacement on a typical garage or extension in this region costs broadly in the range of £800 to £2,500 or more, depending on size, system chosen and deck condition. EPDM rubber systems tend to have a higher material cost than felt but fewer seams, which reduces the number of potential failure points over time.
A contractor cannot tell you repair or replace without getting on the roof. The assessment should include checking the surface condition across the whole area, not just where the leak has appeared inside. Leaks often travel, so water entering at the wall junction above a bathroom may be dripping through a ceiling several metres away. The contractor needs to find where it is actually getting in, not just where it is coming out.
The deck should be walked carefully to identify soft spots. The outlet or gully should be checked for blockages and checked that it sits correctly within the membrane. Flashings at every wall junction and at any pipes or vents should be inspected individually.
When a contractor recommends replacement, ask them to show you why. They should be able to point to the condition of the membrane, the deck, or both. If they cannot give you a clear reason beyond "it's old", ask more questions. Equally, if they recommend only a repair on a roof that you know has been patched before, ask them what is different this time and why it will hold.
Ask specifically whether they are going to strip the existing covering before laying anything new. Overlaying a new membrane on top of an old, damp one is a common shortcut that shortens the life of the new system and hides problems that will resurface.
For replacement work, the two main systems we use are mineral felt, laid in multiple bonded layers, and EPDM rubber membrane. Felt is a well-understood system that has been used for decades. EPDM is increasingly common on extensions and garages because a single large sheet covers most surfaces with very few seams. Both are appropriate for flat roofs on domestic buildings.
No obligation · We usually respond within 2 hours
Storm damage, active leak, damaged ridge - we aim to be on-site within 24 hours.
