Felt has a poor reputation, and most of that reputation was earned by single layer pour and roll work from decades ago. Modern high performance torch on felt is a different product: two or three layers of polyester reinforced bitumen bonded together, with a mineral cap sheet on top. Installed properly it is a genuine 15 to 20 year roof at the lowest cost of any system we fit.
Modern torch-on built up felt: the budget option done properly, plus repairs to existing felt roofs.
What modern felt actually is
A built up system starts with a vapour control layer or underlay bonded to the deck, then an intermediate layer, then a mineral finished cap sheet torched down so the layers fuse rather than sit on each other.
The mineral surface protects the bitumen below it from UV, which is what killed the old single layer roofs. The polyester reinforcement lets the sheet move without tearing.
Felt is the sensible choice when the budget is the deciding factor, when the roof is a detached garage or outbuilding rather than living space below, or when you are matching an existing felt system on a shared or adjoining structure.
Lowest upfront cost of the three main systems
Very good on complex shapes with many upstands and awkward junctions
Easy and cheap to repair locally when something does go wrong
Readily matched to existing felt on adjoining buildings
It has the shortest life of the three systems, typically 15 to 20 years against 25 to 30 for EPDM and GRP. It has seams, and seams are where roofs fail. It involves hot works, which we manage carefully but which is a genuine consideration next to timber or a fascia board.
Blistering happens where moisture is trapped underneath, usually because the deck was damp when the felt went on. That is an installation issue rather than a material issue, and it is one of the main reasons we insist on a dry deck.
Repairing an existing felt roof
Not every failed felt roof needs replacing. Where the deck is sound and the failure is localised, splits and lifted laps can be cut out and re-torched, and blisters can be cut, dried and patched.
Where the felt has gone brittle across the whole roof, water is trapped in the deck, or the roof holds standing water because the falls are wrong, a repair is throwing money at it. We will tell you which situation you are in.
How long does a felt roof last?
A modern three layer torch on system typically lasts 15 to 20 years. Old single layer pour and roll felt often failed inside ten, which is where the material's reputation came from.
Can my blistered felt roof be repaired?
Often yes. Isolated blisters can be cut, dried and patched. Widespread blistering usually means moisture is trapped in the deck, and then replacement is the honest answer.
Is felt cheaper than EPDM?
Yes, upfront, typically by a meaningful margin on a small roof. Over the life of the roof the gap narrows considerably because EPDM lasts longer.
Do you use a torch near timber?
We take hot works precautions, use heat shields at vulnerable junctions and switch to cold applied detailing where the risk is not worth taking. On some roofs we will recommend EPDM instead purely for that reason.
Can felt be laid over an old felt roof?
Only on a dry, sound, well bonded existing system. Overlaying a wet roof traps the moisture and guarantees blistering.
We probe for soft spots and trapped moisture, because felt over a wet deck blisters within a season or two.
Number of layers, cap sheet type and any insulation stated in the quote.
Old covering removed, deck repaired or replaced, and left dry before anything is torched.
Underlay, intermediate and cap sheet bonded, with hot works precautions around timber and fascias.
Upstands, drips and outlets finished, then flushed and checked before sign off.
Evans Roofing & Maintenance Ltd, Witney, Oxfordshire. Call 07960 482233 for a free written quote.