Flat Roofs
Flat roofs on garages, extensions and dormers, laid on a deck that has been checked first.
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Felt flat roofs in Windsor, Berkshire and South West London, built up in three torch-on layers with a mineral cap sheet on a properly prepared deck. Book a free roof inspection and you get photos of your roof and a fixed written quote before any work starts.
Say "felt roof" and most people picture a single sheet of black felt nailed onto a shed, blistered and split after a few summers. That is not what a built-up felt flat roof is.
A modern felt roof is three layers of reinforced, polymer-modified bitumen membrane, each one heated with a torch and bonded fully to the one below:
Because the layers are bonded and their joints are staggered, there is no single seam running through the roof for water to follow. It is a proven, cost-effective system that suits garages, extensions, dormers and large flat roofs alike.
Torching is skilled work. Done properly, every layer is fully bonded with no dry spots and no scorched timber.
Old covering off, joists checked and a new deck laid to falls wherever the old one has failed.
The first two layers torched on and fully bonded, with laps staggered so no joint lines up with another.
The top layer torched down, with the mineral finish facing up to protect the roof from the sun.
Felt dressed up the upstands and abutments and flashed in, then drip trims and edge trims fixed all round.
The flat part of a felt roof rarely fails first. The edges do: the upstand where the roof meets the house wall, the drip edge over the gutter, the outlet and the corners. Cheap felt roofs skimp there, with the felt stopped short of the wall or a strip of mastic doing the job lead and proper dressing should do.
On every felt roof we lay, the felt is carried up the upstands and abutments and flashed in, so water is turned away from the junction instead of finding its way behind it. Drip trims are fixed at the gutter edge so water drops clear into the gutter, and edge trims finish the other sides. Door thresholds that open onto the roof are dressed so the roof and the door work together.
On our Hampton job the felt was finished with a grey mineral cap sheet, new edge trim and the upstand dressed in against the parapet.
Felt is the most affordable of the three flat roof systems we fit. Our flat roof cost guide puts a single garage roof in torch-on felt at £1,000 to £1,800 for 2026, including the strip, deck check, three-layer felt system and trims. An extension roof of 15 to 25 square metres in felt is £1,500 to £2,800, including upstands, drip trims and flashing into the house wall.
A dormer flat roof re-cover is £600 to £1,500: small areas but fiddly details, with access driving the price. If the deck has failed and has to be replaced, that is part of the quote and you see it before you agree anything.
Felt costs less than EPDM and GRP, and it is a sound choice on a tight budget or a large roof. If you want the longest life or a roof with no naked flame near timber, we will show you the EPDM and GRP prices alongside, in writing.
One of the largest flat roofs we have covered this year, running across several wings of a house in Fleet at different levels. Re-covered in a felt system with a grey mineral cap sheet and new black edge trims, under the same scaffold as the pitched re-roof. Every photo is from the job.
Tell us about the roof, garage, extension or dormer, and we will book a free inspection and give you a fixed written quote. Prefer to talk first? Call us any time.
Tell us about the job, we usually reply within the hour.
Prefer to talk? Speak to Cornelius on 01753 330566 or
Expert Roofer Verified member“Seal Pro Roofing did a superb job on our roof replacement. They were punctual, tidy and kept us informed throughout. The workmanship was excellent and the price was fair. Very impressed with their customer service and would happily use them again in future.”
“Seal Pro Roofing delivered a great service. The team were knowledgeable and worked carefully to ensure everything was done properly. The roof looks solid and well finished. Very happy with the professionalism shown.”
Flat roofs on garages, extensions and dormers, laid on a deck that has been checked first.
Flat roofs →
A single rubber membrane with no seams across the main roof, laid with no naked flame.
EPDM Rubber Flat Roofs →
One hard, jointless fibreglass skin on a new deck, ideal for roofs you walk on.
GRP Fibreglass Flat Roofs →
Splits, blisters, ponding and failed upstands repaired, with an honest answer on repair or replace.
Flat Roof Repair →Free written quotes. 24hr emergency callout. A local team rated 5.0 by 150+ homeowners on Bark.