Felt Flat Roof Costs UK — What to Charge to Install a Felt Roof in 2026

What to Charge for a Felt Flat Roof in 2026

For a modern torch-on (high-performance built-up felt) roof supplied and installed, you're typically looking at £70–£110 per m² across most of the UK, with London and the South East pushing toward the top of that band and beyond. Cheaper mineral felt sits at the low end; full three-layer SBS torch-on systems with proper trims and a guarantee sit at the higher end.

On a per-job basis, that works out roughly as follows for common flat-roof sizes:

• Small garage or single-storey extension (15–25m²): £1,200–£3,000
• Medium extension or larger garage (25–40m²): £2,500–£4,500
• Large flat roof (40–70m²): £4,000–£7,500+

Most felt roofs are a 1–3 day job for a two-person team. A straightforward garage strip-and-recover is often a single day; an extension with new deck, insulation, multiple upstands and trims runs to two or three. Day rates for a competent felt roofer and labourer sit around £350–£600 per day combined depending on region — build that into your per-m² figure rather than quoting it separately, or you'll look expensive against operators who hide it.

The Different Felt Systems — and Why Price Varies So Much

The single biggest driver of price on a felt roof is which system you're laying. Customers rarely understand the difference, so it's on you to explain why two quotes for "a new felt roof" can be hundreds of pounds apart.

Pour-and-Roll / Mineral Felt (Budget)

The cheapest option is traditional pour-and-roll, where hot bitumen is poured from a bucket and the felt rolled into it, or a basic mineral-surfaced felt bonded with cold adhesive. It's quick, it's cheap, and it's what a lot of older garage roofs were done in. The trade-off is lifespan: budget mineral felt typically lasts only 10–15 years before it cracks, blisters and lets water in, and it's far less tolerant of standing water and movement.

Materials for a basic mineral felt system are cheap, so you can land this at the bottom of the per-m² range. Be honest with the customer about the shorter life — quoting cheap felt and letting them assume they're getting torch-on is how you end up with a callback and a bad review.

Modern Torch-On Built-Up Felt (Standard)

The professional standard today is torch-on built-up felt: two or three layers of SBS- or APP-modified bitumen membrane, heat-welded together with a gas torch. A typical specification is an underlay/vapour layer, an intermediate layer and a mineral-surfaced cap sheet. The modified bitumen is far more flexible and UV-stable than old mineral felt, so a well-laid three-layer torch-on roof commonly lasts 20–25 years and carries a manufacturer-backed guarantee.

Torch-on costs more because the materials are more expensive, the labour is more skilled, and the job takes longer — every lap is heat-welded by hand and the detailing around upstands and trims is fiddly. SBS-modified felt suits the UK climate well (it stays flexible in the cold); APP is more heat-resistant. That extra cost buys roughly double the lifespan of budget felt, which is the argument you make to a customer weighing the two.

This is also where felt is distinct from the alternatives a customer may be comparing. GRP fibreglass is a wet-laid resin-and-matting system with no hot flame and a seamless finish; EPDM is a single-ply rubber membrane laid in one sheet and glued down. Felt is the cheapest of the three to buy in and the most forgiving to repair, which is why it still wins the most garage and extension work.

What Drives the Price of a Felt Roof

Two felt roofs of the same area can differ by 50% in price depending on what's underneath and around them. These are the factors that move your quote:

• Roof area: the headline number, but always measure the true deck area including the run up every upstand, not just the plan footprint.
• Stripping and disposal: removing the old covering and getting it to a skip is labour and tip fees. Old felt is heavy and bitumen-bonded — allow for a half-day strip on a typical garage and price the skip or waste-carrier charge in.
• Deck condition and replacement: the biggest hidden cost. If the existing deck is soft, delaminated or rotten you'll be re-boarding in 18mm OSB3 or exterior-grade ply. Always price a contingency for this — see below.
• Upstands, abutments and flashings: every wall the roof meets needs an upstand and a flashing or cover detail. A simple square garage has four straightforward edges; a roof tucked between two walls with an abutment to the house is far more labour.
• Drip trims and edge detail: proper aluminium or GRP drip trims at the eaves and gable edges are a material and labour line in their own right — don't leave them out of the quote.
• Insulation — warm vs cold roof: a warm roof (insulation above the deck) is the modern, Building-Regs-compliant approach for habitable spaces and adds the cost of PIR boards and a vapour control layer. A cold roof (insulation between joists) is cheaper but must be ventilated to avoid condensation.
• Penetrations: chimneys, soil pipes, rooflights and vents each need cutting, dressing and sealing — every penetration is extra detailing time and a potential leak point.
• Access: a ground-floor garage you can reach off a ladder is cheap; a first-floor flat roof needing scaffold or a tower adds access cost and time.
• Hot works and fire risk: torch-on means an open gas flame next to timber and, often, the customer's house. That carries real fire risk, needs the right insurance, fire extinguishers on site and a fire-watch period after you finish — and that responsibility is part of what your price covers.

Building Regulations, Decks and Insulation

A re-covering that doesn't touch the structure or insulation is generally treated as repair and doesn't need a Building Regs application. But the moment you renew more than 25% of the roof, replace the deck, or change a roof over a habitable room, Building Regulations bite — and the key requirement is thermal performance.

For a flat roof over a heated space, you're expected to hit a U-value around 0.18 W/m²K on a renovation, which in practice means a warm-roof build-up with 100–150mm of PIR insulation above the deck, a vapour control layer below it and the felt on top. The deck itself should be 18mm OSB3 or exterior-grade plywood fixed to firrings that give a fall of at least 1:80 (aim for 1:40 in practice so water actually runs off).

Insulation and deck replacement are where a "cheap felt roof" quietly becomes an expensive one. A garage roof with no habitable space below it can be a simple cold deck and recover; an extension over a kitchen needs the full warm-roof build-up to comply. Always establish what's below the roof before you price it, and make clear in your quote whether you're providing a compliant insulated build-up or a like-for-like recover.

Lifespan and Guarantees

Lifespan is your strongest selling point for the more expensive system, so put real numbers in front of the customer:

• Budget mineral / pour-and-roll felt: 10–15 years, usually with little or no meaningful guarantee.
• Two-layer torch-on: 15–20 years, often a 10-year workmanship guarantee.
• Three-layer SBS torch-on: 20–25 years, with manufacturer-backed guarantees of 10–20 years available if you're an approved installer.

Frame it as cost-per-year, not headline price. A torch-on roof at £2,400 lasting 22 years is roughly £109 a year; a budget felt roof at £1,400 lasting 12 years is £117 a year — and that's before the disruption of doing it twice. That framing wins more torch-on jobs than any discount.

Quick Reference: Felt Roof Costs UK 2026

Worked Example: Pricing a Typical Garage Felt Roof

Take a detached single garage with a tired, blistered felt roof. You measure it at 4.5m × 4.0m = 18m² of deck. The customer wants a long-lasting job, so you quote a three-layer SBS torch-on system. There's no habitable space below, so a warm-roof build-up isn't needed, but on inspection two boards near the gutter are soft and will need replacing.

• Three-layer torch-on, 18m² at £85/m²: £1,530
• Strip and dispose of old felt + skip share: £250
• Replace 4 deck boards (18mm OSB3) plus labour: £180
• New aluminium drip trims to two gable edges and eaves: £160
• Dress around soil-vent pipe penetration: £80

That totals around £2,200 for a roughly 1.5-day job — comfortably inside the £1,200–£3,000 garage range and at a healthy margin. Note how the felt itself is only about two-thirds of the price: the strip, deck, trims and detailing make up the rest, and they're the lines an inexperienced quoter forgets.

Quoting Tips for Felt Roofs

Felt-roof quotes go wrong in two predictable places: the deck and the hot works. Cover both and you'll keep your margin and stay safe.

• Always price a deck contingency. You can't see the full state of the deck until the old covering is off. Either include a per-board allowance in your quote with a clear note that significant additional rot will be charged at a stated rate, or quote a provisional sum for deck repair. Walking the roof and feeling for soft spots before you price reduces surprises, but never assume a clean strip.
• Build hot-works safety into the price. Torch-on means an open flame near timber, fascias and the customer's home. Carry the right liability insurance, have extinguishers and a damp-down kit on site, keep the torch away from eaves and roof edges where flame can track into the void, and observe a fire-watch period of at least an hour after you down tools. This is a genuine cost and a genuine responsibility — don't cut it to win a job.
• Separate the spec from the price. State clearly whether you're quoting budget mineral felt, two-layer or three-layer torch-on, and what guarantee comes with it. A like-for-like comparison only works when both quotes describe the same system.
• Confirm what's below the roof. Habitable space pulls Building Regs and warm-roof insulation into scope. Establish this before you quote, not after.
• Quote falls and drainage. If the existing roof ponds water, firrings to create a proper fall are extra labour and timber — flag it rather than felting over a flat, water-holding deck.

A felt-roof quote that lists the system, the strip, the deck contingency, the trims and the guarantee — rather than one lump sum — wins more work and protects you when the deck turns out worse than the customer hoped. It shows you know the job, and it gives you a clear paper trail when extras come up.