A garage roof is one of the most common flat roofing jobs in the UK — and one of the most straightforward, provided you choose the right material and the right contractor. Yet many homeowners end up spending money twice: once on a cheap felt replacement that fails within 5–8 years, and again on the proper system they should have installed the first time.
This guide gives you clear, realistic costs for every garage roof replacement option available in the UK in 2026, explains what drives the final price, and helps you decide which material is the smartest investment for your situation.
Garage Roof Replacement Costs at a Glance — 2026
All prices below cover a standard single garage (approximately 15–18m²). Costs include strip of old roof, disposal of waste, supply and installation of new membrane or tiles, and all associated labour. Double garage costs are typically 60–80% more than single garage prices for the same material.
Each Material Explained: Cost, Lifespan, and Verdict
Standard Roofing Felt (3-Layer System)
Traditional mineral-surface roofing felt is the most common garage roof material in the UK, and the cheapest to install. A proper installation uses three layers — a base layer, an intermediate layer, and a cap sheet — bonded with cold adhesive or bitumen. When installed correctly by an experienced roofer, a 3-layer felt system performs adequately for 10–15 years.
The problem is that felt is highly vulnerable to UV degradation, thermal cycling, and ponding water — all of which are typical conditions for a flat garage roof in the UK. Blistering, cracking, and lap joint failures are common from year 8–10 onwards. Most homeowners who chose felt last time are replacing it again when they read this guide. If budget is genuinely the only constraint, felt is a viable short-term solution — but it should be seen as a 10-year fix, not a permanent one.
Torch-On Modified Bitumen Felt (SBS)
Torch-on felt — also called modified bitumen or SBS felt — is a significantly upgraded version of standard felt. It uses a styrene-butadiene-styrene (SBS) polymer modifier that makes the bitumen more flexible and resilient. Sheets are heat-welded together using a gas torch rather than cold-bonded, creating fully-fused laps with no cold adhesive joints that can fail over time.
Torch-on systems perform noticeably better than standard felt in thermal cycling and UV resistance, and the heat-welded laps eliminate one of the primary failure points of conventional felt. It is a reasonable step up from standard felt for homeowners who want better longevity without the premium cost of EPDM or GRP, and it is widely installed by experienced roofers across the UK.
EPDM Rubber Roofing
EPDM (ethylene propylene diene monomer) is a synthetic rubber membrane that has become the go-to material for quality flat roof replacement in the UK over the past decade. It is laid as a single piece with no seams across the main deck — the biggest single advantage over any felt system — and bonded to the roof deck using a specialist adhesive. Upstands and trims are finished with compatible EPDM flashing tape or seam tape.
The single-sheet application means there are no lap joints to fail. EPDM is highly resistant to UV degradation, ozone, and thermal movement — it remains flexible from -45°C to +150°C, meaning the freeze-thaw cycling that cracks felt has no effect on it. It is also straightforward to repair if punctured: a simple patch kit and EPDM adhesive is all that is needed. The material is the same product used on commercial and industrial flat roofs worldwide, and its track record in the UK is now well established.
GRP Fibreglass Roofing
GRP (glass reinforced polyester) fibreglass roofing is a rigid, seamless system that cures to a hard, smooth surface. Installation involves laying chopped strand matting over the roof deck, saturating it with liquid polyester resin, allowing it to cure, and then applying a coloured topcoat (gelcoat) that provides UV protection and a finished appearance. The result is a monolithic, fully bonded, hard surface with no seams, laps, or joints anywhere on the main deck.
GRP is the hardest and most impact-resistant of the flat roof materials commonly used on garages — it can bear foot traffic, resists puncture from falling debris, and is unaffected by UV or thermal cycling. It is slightly less flexible than EPDM and in very rare cases can crack under significant structural movement, but on a stable garage structure this is very unlikely. Installation requires a trained GRP applicator working in appropriate temperature conditions — GRP cannot be laid in temperatures below around 5°C.
Liquid Waterproofing Membrane
Liquid-applied waterproofing systems — such as polyurethane (PU) or PMMA-based products — are cold-applied coatings that cure to form a seamless, fully-adhered membrane directly on the roof deck. They are applied by brush, roller, or squeegee in one or two coats, often with a reinforcement fleece embedded in the base coat at upstands and detail areas. Because they are applied as a liquid, they conform perfectly to any shape, detail, or penetration without the cutting and joining required for sheet membranes.
Liquid systems are particularly well-suited to garages with complex details — multiple penetrations, irregular shapes, or awkward upstands — where sheet membranes are harder to terminate neatly. Quality is highly dependent on the skill of the applicator and the specific product used — premium PMMA systems (such as Sika Trocal or Kemperol) significantly outperform cheaper polyurethane coatings.
Side-by-Side Comparison
| Material | Single Garage Cost | Lifespan | Maintenance | Best For |
|---|---|---|---|---|
| Standard felt | £600–£1,200 | 10–15 yrs | Annual check | Tight budget, short-term |
| Torch-on felt (SBS) | £750–£1,400 | 15–25 yrs | Every 3–5 yrs | Budget with better longevity |
| EPDM rubber | £800–£1,600 | 25–50 yrs | Very low | Best all-round value |
| GRP fibreglass | £1,000–£2,000 | 25–40 yrs | Very low | Hard, durable, premium finish |
| Liquid waterproofing | £700–£1,400 | 15–25 yrs | Low | Complex shapes and details |
| Pitched tile | £2,500–£5,000 | 40–60 yrs | Very low | Matching house roof, aesthetics |
What Affects the Final Cost?
Garage Size
A single garage is typically 15–18m². A double garage is 28–35m². Material costs scale almost linearly with area, while some labour costs (call-out, setup, waste disposal) are fixed regardless of size — meaning larger garages have a lower cost per m².
Decking Condition
The OSB or timber boards beneath the membrane must be solid and dry. Rotten, soft, or delaminated boards must be replaced before the new membrane is installed — adding £300–£700 for a single garage depending on how much decking needs replacing. This is the most common additional cost.
Fascia and Trim Condition
Rotten fascia boards or deteriorated drip trims need replacing before the new roof is laid. Fascia replacement typically adds £100–£300 depending on the extent, and is often recommended when the roofer strips the old roof and can see the underlying timber condition clearly.
UK Region
Labour costs vary by 20–40% across the UK. London and the South East command the highest rates. Yorkshire, the Midlands, and the North typically run lower. Scottish islands and remote areas may carry additional travel costs for specialist contractors.
Upstand and Detail Complexity
A simple rectangular garage roof with a single outlet is the most straightforward. Skylights, roof lights, soil vent pipe penetrations, internal gutters, or complex parapet details all increase installation time and material use — typically adding £100–£400 per complex detail.
Access and Height
A standard detached single garage is easily accessible from a standard ladder. An integral or attached garage where the roof is at first-floor height may require tower scaffold for safe access — adding £150–£300 to the job cost.
Time of Year
GRP fibreglass cannot be installed below approximately 5°C — meaning winter installations may not be possible without a heated workspace. EPDM is more tolerant of cold conditions. Spring and summer installations typically have shorter waiting times and avoid cold-weather restrictions.
Waste Disposal
Stripping the old roof produces significant waste — old felt, insulation, and sometimes decking boards. Skip hire or trade waste removal costs are typically included in quotes from established contractors, but worth confirming. Budget £100–£200 if managing waste separately.
Repair vs Full Replacement: How to Decide
Not every leaking garage roof needs a full replacement. A repair is viable in specific circumstances — but it is also frequently the wrong choice when a full replacement would be more cost-effective over any reasonable time horizon. Here's how to think through it:
✅ Repair is viable if…
- Existing membrane is less than 10 years old
- Damage is isolated to one specific area — a single split or blister
- Roof decking beneath is solid — no bounce or softness underfoot
- The system type is compatible with patch repair (EPDM patches easily; old felt is more difficult)
- No previous repairs have already been attempted and failed
❌ Full replacement is the right choice if…
- Existing felt is 15+ years old with widespread cracking or blistering
- Leaks have occurred in multiple areas at different times
- Decking boards are soft, bouncy, or visibly rotten
- Previous repairs haven't held for more than a few years
- Ponding water is present — indicating falls have failed
- Upgrading the material to avoid the cycle of repeated repairs
What the Replacement Process Involves
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1Strip of existing roof covering
All old felt, insulation, and any loose or rotten decking boards are stripped back. The roofer assesses the condition of the deck and fascias at this point and reports any additional work required before quoting for it — not assuming it in the original price.
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2Decking inspection and replacement where needed
Any soft, rotten, or delaminated OSB or timber board sections are replaced with new pressure-treated timber or OSB3. This is critical — a new membrane laid over poor decking will fail early at the soft points.
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3Check and correct the fall
A flat roof must have sufficient fall — typically 1:40 or steeper — to drain water toward the outlet. Where falls are insufficient and ponding is occurring, tapered insulation can be installed to correct drainage without structural alteration.
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4Installation of new membrane or covering
The new material is installed according to manufacturer specifications. For EPDM this means priming, bonding adhesive, rolling out the sheet, and trimming. For GRP this means laminating the glassfibre, curing, and applying the gelcoat topcoat. Upstands, trims, and outlets are all detailed at this stage.
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5Gutters, downpipes, and fascias checked and cleaned
A complete job includes clearing the gutters of any debris from the old roof stripping, checking the outlet is clear, and ensuring downpipes are flowing freely. Any rotten fascia sections identified during the strip are replaced.
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6Final inspection and guarantee documentation
A reputable roofer provides a written guarantee on completion — typically 10 years for EPDM or GRP systems — along with photos of the completed work. Keep this documentation safe; it may be needed for insurance purposes or when selling the property.
Getting the Best Price: What to Look For in Quotes
- ✓ Get at least three written quotes specifying the material, thickness/specification, and guarantee period
- ✓ Check whether decking replacement is included or treated as a variable extra — and if variable, ask the roofer's assessment of how much may be needed
- ✓ Confirm waste disposal is included — some quotes exclude skip hire
- ✓ Ask for photos from previous comparable jobs (flat garage roofs, same material)
- ✓ Check the roofer has public liability insurance — ask for the certificate
- ✓ For EPDM: ask whether they use a full-bond or partially-bonded system and which EPDM brand (Firestone and Carlisle are market leaders)
- ✓ For GRP: ask whether they are a trained applicator for the system they're using — GRP quality is highly installer-dependent
- ✓ Confirm the guarantee is from the contractor, not just the material manufacturer — and what the process is if a problem arises
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Frequently Asked Questions
How much does garage roof replacement cost in the UK?
Garage roof replacement costs in the UK typically range from £600 to £4,000 depending on the garage size, roofing material, and whether any decking repairs are needed. A standard single garage with a new felt roof costs £600–£1,200. EPDM rubber on the same garage costs £800–£1,600. GRP fibreglass costs £1,000–£2,000. A double garage increases costs by 60–80%. Pitched tile replacement starts from £2,500.
What is the best material for a garage roof replacement?
EPDM rubber and GRP fibreglass are the two best materials for a flat garage roof replacement in the UK. Both significantly outperform traditional felt in durability — EPDM lasts 25–50 years and GRP 25–40 years, compared to 10–15 years for standard felt. GRP provides the hardest and most impact-resistant surface; EPDM is slightly more flexible and easier to repair if punctured. Both are considerably better long-term investments than replacing felt with felt.
How long does a garage roof replacement take?
A standard single garage roof replacement typically takes one to two days. Felt replacement is often a single day job. EPDM installation takes one to two days including adhesive curing time. GRP fibreglass typically takes two days — one day for the glassfibre laminate and a second day for the topcoat once the base has cured. Additional time is needed if decking boards require replacement.
Do I need planning permission to replace a garage roof?
In most cases, replacing a garage roof with the same or similar material does not require planning permission in England and Wales under permitted development rights. However, changing the pitch or height of the roof, using a materially different appearance in a conservation area, or work on a listed building will require consent. Always check with your local planning authority if you are in any doubt, particularly if considering a significant change to the roof design or structure.
Can I repair my garage roof instead of replacing it?
Repair is viable when the existing roof membrane has isolated damage — a single split or blister in otherwise sound felt or EPDM — and the roof decking beneath is structurally sound with no rot or softness. If the felt is over 15 years old with widespread cracking or blistering, decking boards are soft or bouncy underfoot, or there have been recurring leaks in multiple areas, full replacement is almost always more cost-effective than repeated patching.
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