If your garage, extension or outbuilding has a flat roof that is more than fifteen years old, the chances are it is either leaking already or quietly heading that way. Traditional mineral felt flat roofs were the standard for decades across High Wycombe, from the post-war garages of Booker and Loudwater to the extension roofs of Hazlemere and Holmer Green, but they have a finite lifespan and they do not age gracefully.
At Kingsway Roofing we replace old felt flat roofs with modern, high-performance systems engineered to last twenty-five years and more. We install EPDM rubber membrane and GRP fibreglass flat roofing across High Wycombe and the Chilterns, using our own employed team, never subcontractors. Every installation comes with a free survey, a fixed written quote and a workmanship guarantee of up to 25 years.
The difference between a modern flat roof and an old felt one is not just the material. It is the quality of the deck preparation, the detailing at the edges and upstands, and the standard of the installation. A badly fitted EPDM membrane will fail just as surely as a badly laid felt roof. That is why we take the time to prepare the substrate properly before any membrane goes down.
Why Choose Kingsway in High Wycombe
What We Deliver
Modern EPDM rubber and GRP fibreglass systems with 25-30+ year lifespans
Full timber deck inspection and replacement where required. No covering over rot.
Free no-obligation survey with drone photography and honest assessment
Written workmanship guarantee of up to 25 years on every flat roof installation
No subcontractors. Our own High Wycombe team surveys and fits every roof.
No deposit required. You pay only when the work is complete and you are satisfied.
Insurance-backed guarantees available on request
Modern GRP Fibreglass & EPDM Rubber vs Outdated Mineral Felt
The flat roofing industry has moved on significantly from the days of pour-and-roll bitumen felt. If you are weighing up your options for a High Wycombe property, here is a straightforward comparison of the three main approaches we work with.
Traditional mineral felt
The old standard. Cheaper upfront but susceptible to blistering, cracking and ponding. Typical lifespan of 10-15 years before problems begin. We will repair sound felt roofs, but for full replacements we recommend modern systems.
EPDM rubber membrane
A single-ply synthetic rubber membrane that is fully bonded to the deck. Exceptionally UV-stable, flexible in all temperatures and resistant to ponding water. Lifespan of 30+ years. Ideal for domestic extensions and garages across High Wycombe.
GRP fibreglass (Glass Reinforced Plastic)
A cold-laid laminate that cures into a single, seamless, rigid shell. Completely waterproof, impact-resistant and ideal for flat roofs with complex shapes or foot traffic. Lifespan of 25-30+ years with zero maintenance.
Tackling Common Flat Roof Faults
Most of the flat roof replacements we carry out across High Wycombe are prompted by the same handful of warning signs. Ignoring them does not save money. It usually means a more expensive repair later, once timber decay has set in.
Ponding water on the surface
Water that sits on a flat roof for more than 48 hours after rain is a sign that the fall (slope) has been lost or was never adequate. Standing water degrades the surface, adds weight and eventually finds its way through. Common on older garage roofs across HP11 and HP12.
Torn and blistering felt
Blisters form when trapped moisture or air expands beneath the felt on hot days. Once the surface cracks, water enters the substrate. If you can see blistering or tearing from the ground, the roof is nearing the end of its life.
Timber rot in the deck
Once water penetrates the felt, the timber deck beneath begins to rot. A spongy or springy flat roof is a sign of structural decay. Replacing the membrane without addressing rotten timber is a waste of money. We always inspect and replace deck boards as part of a proper replacement.
Poor insulation and condensation
Older flat roofs across High Wycombe often lack adequate insulation, leading to condensation forming on the underside of the deck in winter. Modern replacement systems include insulation upgrades that bring the roof in line with current Building Regulations and eliminate condensation.
Free Site Survey & Roof Assessment
Up to 25-Year Workmanship Guarantee
Fully Insured Local Roofing Specialists
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What High Wycombe Customers Say
Trusted by Homeowners Across High Wycombe
Genuine reviews from homeowners across High Wycombe and the surrounding Chiltern Hills villages.
James W.
Downley, High Wycombe
A winter storm off the Chilterns lifted half a dozen slates off our Downley roof. Kingsway came out the next morning, matched the slates and had them refixed by lunchtime. No drama, no upselling, just a proper repair with a guarantee. First class.
Emma L.
Hazlemere, High Wycombe
Our garage flat roof had been ponding and splitting for years. Kingsway replaced it with a GRP fibreglass system in two days. The finish is seamless and the team left everything spotless. I only wish we had done it sooner.
Patrick D.
Flackwell Heath, High Wycombe
Damp was tracking through around the chimney breast in our Flackwell Heath cottage. Kingsway repointed the stack and replaced the lead flashing with Code 5 lead. Not a drop of water since. Genuinely skilled craftsmen.
Susan H.
Loudwater, High Wycombe
We had our whole roof stripped and re-laid with natural Spanish slate after the original concrete tiles started cracking. Kingsway handled everything: scaffolding, skip, Building Regs sign-off. The result is stunning. Worth every penny.
Graham F.
Holmer Green, High Wycombe
Ridge caps were crumbling and water had started getting into the loft. Kingsway surveyed it properly with a drone, showed me the photos and gave me a fixed quote on the spot. Repair done in a day, with a guarantee. No complaints at all.
Carol M.
West Wycombe, High Wycombe
An unused chimney pot was letting rain straight down the flue. Kingsway fitted a ventilated cowl and repointed the whole stack. They even matched the mortar colour to the original. A proper job by people who clearly know their trade.
See Our Other Roofing Services in the Area
More High Wycombe Roofing Services
Emergency leak repairs, slipped slates and storm damage across High Wycombe.
Repointing, lead flashing replacement and chimney pot capping.
Complete new roof installation and re-roofing in slate and tile.
Need a complete roof replacement or a full inspection? Visit our main Roofers High Wycombe hub to explore every local roofing service we offer across HP10, HP11, HP12, HP13, HP14 and HP15.
Common Questions
Flat Roof Replacement in High Wycombe: Your Questions Answered
How long does a flat roof replacement take in High Wycombe?
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Most domestic flat roof replacements, such as a garage or single-storey extension, are completed in one to two days. Larger or more complex roofs with multiple upstands and details may take three to four days. We strip the old roof, inspect and replace any rotten timber, fit the new system and finish the detailing in a single continuous visit. You will be given a realistic timeframe in your written quote.
Should I choose EPDM rubber or GRP fibreglass?
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Both are excellent systems and either will outlast traditional felt by decades. EPDM is ideal for straightforward flat roofs and domestic extensions: it is flexible, UV-stable and very quick to install. GRP fibreglass is better for roofs with complex shapes, multiple upstands or where foot traffic is expected, as it cures into a rigid, seamless shell. We will recommend the right system for your specific roof after the survey.
Can you replace the flat roof on my High Wycombe garage?
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Yes. Garage flat roof replacement is one of the most common jobs we carry out across High Wycombe, from the post-war garages in Booker to the modern blocks in Hazlemere. We strip the old felt, replace any rotten deck timber and install a modern EPDM or GRP system that will last for decades.
Do you need to remove the old felt or can you overlay it?
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We always strip the old roof down to the timber deck. Overlaying new membrane on top of old felt is cheaper, but it traps moisture, hides rotten timber and shortens the life of the new roof. A proper replacement means starting from a sound, dry substrate. Anything else is a false economy.
What guarantee do I get on a flat roof replacement?
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Every Kingsway flat roof replacement carries a written workmanship guarantee of up to 25 years on labour, plus the manufacturer material warranty that applies to the EPDM or GRP system we install. Insurance-backed guarantees are available on request. If the roof fails within its guarantee period due to our workmanship, we return and put it right at no cost.
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