Felt flat roof repair & replacement
In short
Old three-layer bitumen felt blisters, cracks and splits at the seams, and past a certain point patching it is money spent on a covering that has ended. Modern high-performance torch-on felt is a genuinely different product, but the honest question on most old felt roofs is repair or replace.
Also called: Felt roof · Bitumen roof · Torch on felt · Mineral felt roof
Signs you need this
- Blisters or bubbles across the surface of the felt
- Cracking, crazing or a chalky, dried-out look
- Splits along the seams or at the upstands
- Standing water that never drains away
- A deck that feels soft or springy underfoot
- Water staining on the ceiling below
The felt flat roofs that gave the whole idea a bad name went on in the 1960s and 70s: three layers of bitumen felt, bonded hot, with a mineral-surfaced cap sheet. A working life of ten to fifteen years was typical, and a great many of them were laid to no meaningful fall at all — so they ponded, and standing water on bitumen felt is what finishes it.
They fail in recognisable ways. Blisters, where moisture trapped between layers expands in the sun. Cracking and crazing of the cap sheet as the bitumen oxidises and loses its plasticisers. Splits along the seams where the layers were bonded. And at the perimeter, where the felt has been dressed over a timber edge that has since rotted underneath it.
Patch repair is legitimate on a roof with life left in it. A localised split, a blister, a failed detail around an outlet or an upstand — all can be cut out and re-bonded properly, and a roof that is otherwise sound will take that repair well. What does not work is patching a roof that has crazed all over, because the next split is already forming somewhere you have not looked.
The signal that patching has ended is usually the deck. Once water has been getting through for a season or two, the boards below go soft — and a spongy deck under a felt roof means the failure is no longer at the surface. Walking a flat roof and feeling it give underfoot is the practical test, and it is why any honest quote involves getting on the roof rather than looking from a ladder.
Modern torch-on felt deserves separating from its reputation. High-performance polyester-reinforced systems, properly laid in two or three layers with correctly formed details, are a serious covering with a service life measured in decades — and they are still specified widely, particularly on larger and commercial roofs. The stuff that failed in 1978 and the stuff a good roofer lays today are not the same product.
The other thing worth saying plainly is that hot work has a cost. Torching involves an open flame against a timber-decked roof attached to a building, and it carries a genuine fire risk that has burned down real houses. That is one of the reasons EPDM and GRP have taken so much domestic work — no flame at all. Where torch-on is the right answer, the fire precautions are part of the job.
What the job covers
- Honest assessment of whether repair or replacement is right
- Localised cuts, patches and re-bonding where the roof has life
- Deck condition checked by walking the roof, not from a ladder
- Full strip and re-cover where the covering has ended
- Falls formed properly rather than re-covering a ponding roof
- Fire precautions where hot work is genuinely needed
What it costs
We don't publish a price for this yet, because a number pulled out of the air is worse than no number at all — your roofer has to honour it. On roofing it would also be close to meaningless: access is often the biggest single factor, and it varies enormously house to house. You'll get a firm price for your actual job when they ring you back, before any work starts. The quote itself is free and there's no obligation either way.
Common questions
Can my felt roof be patched or does it need replacing?
It depends whether the failure is local or general. One split, one blister, one bad detail on an otherwise sound covering is a repair. Crazing across the whole surface, several splits, or a deck that gives underfoot means the covering has reached the end and patching is renting time at a poor rate.
Is modern felt any good?
Yes — high-performance polyester-reinforced torch-on systems are a long way from the 1970s product and will run for decades when laid properly. The bad reputation belongs to a specific era of material laid to poor falls, not to bitumen roofing as a category.
Why does water sit on my flat roof?
Because it was laid without adequate fall, which was extremely common on older domestic work. A flat roof should achieve a finished fall of at least 1:80, and the trade designs to 1:40 to actually get there. Correcting it means firrings or tapered insulation at re-cover — not simply putting a new covering over the same puddle.
Can a new covering go over the old felt?
It is sometimes done and it is rarely a good idea. It traps whatever moisture is in the old build-up, it bonds a new covering to a substrate that is already failing, and it hides the deck — which on a leaking felt roof is the thing most likely to have rotted. Stripping back is the only way to know what you are covering.
Need this doing in Macclesfield?
Tell us the job and it goes straight to our local roofer — one call back, usually the same day. Free quote, no obligation.