Flat roof replacement in EPDM rubber, GRP fibreglass or felt
Flat Roof Replacement – EPDM, GRP and Felt
Flat roof replacement covers stripping an existing flat roof back to the deck and re-covering it with a modern waterproof system — EPDM rubber membrane, GRP fibreglass or traditional felt — chosen according to the roof's size, detailing and expected lifespan.
Definition
What Flat Roofing covers
Flat roofs are typically covered with one of three systems: EPDM, a single-sheet rubber membrane with few joints and a long lifespan; GRP, a fibreglass and resin system laid and cured in situ, well suited to roofs with complex detailing; or felt, a lower-cost, multi-layer built-up system with a shorter lifespan. Each is supplied over insulation and decking appropriate to the roof's use and current Building Regulations.
Suitable for
- Flat roofs showing ponding water, blistering, cracking or membrane failure
- Garage, extension, dormer and outbuilding flat roofs at the end of their life
- Roofs needing improved insulation as part of re-covering
- New flat roof construction as part of an extension or conversion
Not suitable for
- Isolated small leaks that can be patch-repaired rather than fully re-covered — assessed at survey
- Pitched roofs, which use tile or slate systems rather than flat roofing membranes
Process
How the work is carried out
- 01
Survey
Assessing the existing deck, insulation, falls and the cause of any leaks or ponding.
- 02
Specification
Agreeing the system — EPDM, GRP or felt — based on roof size, detailing and budget.
- 03
Strip and prepare
Removing the existing covering and any damaged decking or insulation, and correcting falls where water is pooling.
- 04
Installation
Fitting new insulation, decking where needed, and the chosen waterproof system with correctly detailed upstands and edges.
Typical timescale
A standard domestic flat roof — garage, dormer or single-storey extension — is typically completed within one to three days, weather permitting; larger roofs take longer.
Cost guidance
Flat roof replacement typically costs £50–£120 per m² in our area — felt sits toward the lower end, EPDM in the middle and GRP toward the top — with insulation upgrades and complex detailing such as upstands, rooflights and multiple abutments adding cost. We provide an itemised quotation after a roof survey rather than a fixed headline price.
Limitations and exclusions
- Decking or insulation found to be damp or rotten once stripped is priced separately as it's identified
- Rooflights, ventilation and access equipment upgrades are quoted separately unless already agreed
- Felt roofs carry a shorter expected lifespan than EPDM or GRP, which we flag at quotation stage
Areas we cover
Flat Roofing across Sussex, Surrey, Kent and South London
Local property styles, planning authorities and neighbourhood coverage for flat roofing in each town we work in.
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FAQs
Flat Roofing FAQs
Which flat roof system should I choose — EPDM, GRP or felt?
EPDM offers a long lifespan with a single membrane and few joints, suiting most domestic flat roofs; GRP suits roofs with complex upstands and detailing since it's laid and cured seamlessly in situ; felt is the lowest-cost option but has the shortest expected lifespan. We advise on the right system for your roof and budget at survey.
Why does my flat roof have ponding water?
Ponding usually means the roof's falls — the slight slope that directs water to an outlet — are insufficient or have settled over time. We assess and correct falls as part of re-covering rather than simply laying a new membrane over the same problem.
How long does an EPDM or GRP flat roof last?
Both typically last 20-30 years or more when correctly installed and detailed, considerably longer than a traditional felt roof. Actual lifespan depends on installation quality, detailing at upstands and edges, and ongoing maintenance.
Discuss your flat roofing project
Tell us about the property and what you have in mind, and we'll arrange a site visit.
Last reviewed 2026-07-28.