The short answer
Felt lifts because it has lost its grip on the deck. Wind gets under a loose edge and peels it back, old adhesive dries and lets go, moisture trapped below blisters the surface, and age makes the felt stiff and brittle. Where only a corner has lifted, a repair can work. Where the felt is lifting in several places, the roof is usually near the end of its life.
A corner of felt flapping in the wind is a warning. Fixing it early can save the deck underneath, and leaving it can let in a winter of rain.
Wind and the edges
Wind does most damage at the edges of a flat roof. Air rushes over the top, pressure drops and the felt is pulled upward. If the edge is only held with a few clout nails, or the adhesive has aged, the sheet starts to flap and then peels back, a little more with every gale.
Why do the corners go first?
Corners and edges take the biggest suction, so they are where the felt needs its best fixing. A properly laid felt roof is bonded along the edge, nailed and sealed under a trim, and the edge detail is dressed over a drip edge, the strip that sheds water into the gutter. When that detail is missing or has worn, the felt has nothing to resist the wind.
You may see the felt flutter, hear it slap in a gale or find a curled strip lying on the lawn. Sometimes the lift is slight, a raised lip along one side. Water runs under the lip, soaks the deck and starts rot in the edge board well ahead of any stain on the garage ceiling.
A tidy edge needs a firm board, a trim that sheds water cleanly and felt that is bonded right to the lip.
Adhesion, blisters and age
Torch-on felt is bonded to the deck by melting its underside with a gas torch. Cold-bonded felts use adhesive instead. Either method fails if the deck was damp, dusty or cold when the felt went on, because the bond never formed across the whole sheet.
What are the bubbles in my felt?
Blisters are pockets of trapped air or moisture between layers. In warm weather the trapped moisture turns to vapour, expands and pushes the felt upward. Small blisters that are intact can sit for years. Once one splits, water gets in and the area softens around it.
Age is the quiet cause. Less puts torch-on felt at 10 to 20 years, and notes that a well-laid roof can reach 20 while a badly laid one may fail inside 10 (Oct 2026). Sunlight dries out the surface, the felt shrinks, and the seams open. An older roof will lift again after any repair, because the material around the patch is tired.
Lifted seams on an ageing roof are a signal to compare repair and replacement. Our garage roof repair or replace guide sets out how we weigh that up.
When a repair holds
A repair holds when the felt is still flexible, the deck is dry and the lift is local. In that case we cut back the loose felt, dry the deck, bond a new patch that overlaps the old by a generous margin and seal the edges. A loose edge is refixed and covered with a trim.
Is brushing on a coating enough?
A coating can help a roof whose felt is still sound, and the page on garage roof paint explains its limits. A coating cannot glue a lifted sheet back down or dry out a wet deck. Laid over a loose edge, it masks the fault until the first hard frost, then peels away with the felt.
Before any patch goes on, we check the deck. Press a screwdriver into boards beside the lifted area. If they are soft, the felt has been letting water in for a while, and the timber needs attention before a new covering. A repair on a rotten deck simply fails again.
MyJobQuote gives an average felt roof price around £1,500, with a 15 m² garage in the range of £1,200 to £1,800 (Oct 2026). A small repair costs far less, and the survey shows which route suits your roof. The garage and asbestos roofs page lists every covering we handle.
When the felt should come off
Several signs point to replacement. The felt lifts in more than one place. Seams have opened along their length. Blisters have split. The surface is cracked in a pattern like dry mud, and a new patch will not bond to it. Water stains show on the ceiling inside. At that point repairs become a series of small bills with no end.
What does a new felt roof involve?
Old felt comes off, the deck is checked and mended, and new layers follow in the order the maker specifies, commonly a base layer and a cap sheet with the joints staggered. The edges are fixed under proper trims. The fall matters, because a flat roof that ponds ages quickly. BS 6229:2025 keeps a minimum finished fall of 1:80, and IKO advises designing for 1:40.
EPDM, a rubber membrane, and GRP, a glass-fibre reinforced plastic, are other options, and our best garage roof material page compares them. Should the survey show that a patch will do, a patch is what you are quoted. Otherwise the photos show why the felt has had its day.
More on lifting felt
Can I stick lifted felt down with roofing adhesive?
For a small corner on a dry deck, it can buy time. The felt must be clean, dry and flexible. On a cold or damp day, or on old brittle felt, the adhesive will not bond, and water gets in behind it.
Is a blister in garage felt serious?
An intact blister is not an emergency, but it is a place where the bond has failed. Once the skin splits, water enters and spreads. Watching it and booking a survey before winter is sensible.
The full picture: Garage and asbestos roof replacement in Taunton · More short answers