Flat Roof Replacement (EPDM / GRP)
A flat roof that is starting to fail usually shows it at the edges first — upstands lifting, trims pulling away, outlets sitting in standing water, or blistering across the field. EPDM and GRP are both reliable long-term systems when installed and detailed correctly. We replace flat roofs on extensions, garages, bay windows and dormers across London and Surrey. Minimum job value: £1,000.
What this service covers
Included work: full flat roof replacement using EPDM or GRP, edge and trim details, upstands, outlets, drainage falls and warm roof insulation upgrades where specified.
- EPDM single-ply and GRP fibreglass systems
- Extensions, garages, bay windows and dormers
- Edge, upstand, outlet and trim detailing included
- Warm roof insulation upgrade option available
Request a flat roof quote
Call 01344 558 785 or use our contact page.
We specify the right system for the roof shape, falls and use — written quote, fully insured, with a photo record on completion.
Why detailing determines whether a flat roof lasts
A flat roof is often judged by the finish on day one, but the real quality shows up over the following winters — in how the edges perform, whether the outlets drain properly, whether the upstands have stayed bonded and whether the trims are still sealing. The field membrane rarely fails first. It is nearly always the details that let water in.
EPDM or GRP?
Both EPDM and GRP can be excellent systems when used in the right context. EPDM rubber roofing offers a clean, durable finish and is popular for domestic flat roofs. GRP fibreglass creates a strong seamless finish with sharp details. The right option depends on the roof shape, layout and finish required.
Warm roof upgrades
Where appropriate, we can factor insulation and warm roof build-ups into the specification. This matters for comfort, condensation control and long-term performance.
Who benefits most from a proper flat roof replacement
Homeowners who have dealt with a leaking garage, extension or bay roof for years are often the best fit for this service. Once a flat roof covering starts to fail at edges, upstands or outlets, repeated small repairs become expensive and frustrating. A properly specified replacement with a quality system gives you a clean slate and a reliable waterproof finish.
Typical related services
When to repair and when to replace a flat roof
Repair makes sense when the membrane across the main field of the roof is still sound and the failure is limited to a single edge detail, an outlet or a small section of trim. A localised fix, properly carried out, can extend the life of a serviceable flat roof. Replacement makes sense when:
- The covering is blistering across the field — not just at one edge
- Water is ponding because the falls have failed or the substrate has softened
- Multiple repairs have been carried out at the same or different locations
- The edge details and upstands have delaminated or are no longer bonded
- The existing system is over 15–20 years old and starting to show widespread deterioration
- The deck beneath has softened from sustained moisture, meaning the substrate needs replacement too
On most of the flat roofs we look at — garage roofs, extension roofs, bay roofs — the membrane across the main field is still serviceable. It is nearly always the perimeter details and junctions where water is actually entering. The inspection determines where the failure sits before we recommend a scope.
FAQs
How do I know if my flat roof needs replacing or just repairing?
The key question is whether the failure is localised or widespread. A single failed edge detail or outlet can often be repaired cleanly. Widespread blistering, multiple failure points, a soft deck, or a history of repeated repairs usually points toward replacement as the better long-term value. Send us photos of the roof — particularly the edges, upstands and any visible cracking — and we can give you an initial view.
Which system is better — EPDM or GRP?
Both are reliable long-term systems when installed correctly. EPDM is flexible and handles movement well, making it a good choice for larger areas and where substrate movement is possible. GRP creates a harder, more seamless finish and is well suited to complex shapes and junction details. We recommend the right system for your specific roof rather than defaulting to one approach for all jobs.
Can insulation be improved as part of a flat roof replacement?
Yes. Where appropriate, we can specify a warm roof build-up — insulation above the deck — which improves thermal performance, reduces condensation risk and can make a meaningful difference to the room below if the flat roof is over a habitable space.
When a flat roof should be replaced
Repeated blistering, ponding, edge failure, cracked joints, failed trims or multiple historic repairs can all point to the need for flat roof replacement rather than more patching. On domestic properties in Surrey and London, many flat roof leaks originate at vulnerable details rather than the middle of the roof, which is why inspection of edges, upstands and penetrations is critical before recommending the right system.
Choosing the right flat roofing system for your property
Most flat roof replacements we carry out in Surrey and London involve ageing felt roofs that have failed at the edges, leaking extension roofs, garage roofs with a history of repeated patches, and bays or dormers where the detailing around upstands and outlets was never properly installed. In most cases the membrane across the main field is still serviceable — it is the perimeter and junctions where water gets in.
We specify EPDM, GRP or other appropriate systems depending on the roof shape, falls, detailing requirements and long-term maintenance expectations. The aim is always to match the system to the roof, not to default to a cheap option that needs attention again in five years.
- EPDM for clean, durable single-ply waterproofing
- GRP for hard-wearing detail-rich domestic flat roofs
- Replacement of failed old felt where substrate and details allow
- Upstands, trims, drip edges, outlets and edge protection
- Integration with skylights, parapets and junctions