⭐ 4.9/5 · 143 Google Reviews — The choice between GRP fibreglass and felt flat roofing on a Leicester property is primarily an economic decision over a 20–40 year horizon. This guide gives Leicester homeowners the information to make that decision correctly.
| Factor | GRP Fibreglass | 3-Layer Felt |
|---|---|---|
| Install cost (20m²) | £1,800–£3,000 | £800–£1,400 |
| Design life | 25–40+ years | 10–20 years |
| Maintenance | Minimal | 5-yearly inspection |
| Leak risk | Very low (monolithic) | Moderate (lap joints) |
| Walkability | Yes (with care) | No |
| Cold weather install | Not below 5°C | Not below 5°C |
| 20-yr total cost | £1,800–£3,000 | £1,600–£2,800 |
| 40-yr total cost | £1,800–£3,000 | £3,200–£5,600 |
The 20-year total cost comparison is where the decision becomes clear. GRP and felt are similar in total cost over 20 years. Over 40 years, GRP is substantially cheaper because it needs no replacement in that period while felt will need replacing at least once and possibly twice. For a Leicester homeowner planning to stay in their property for 10+ years, GRP delivers lower lifetime cost, lower leak risk and less maintenance disruption.
Felt is appropriate in limited circumstances: where the existing deck is too weak or irregular for GRP application without costly remediation; where the budget constraint is absolute and a single GRP installation is unaffordable; or where the property is being prepared for sale in the short term and the investment horizon is less than 5 years. In all other circumstances, we recommend GRP for Leicester flat roof replacements.
EPDM rubber is a third option with a design life of 30–50 years, lower installation cost than GRP (£70–£110/m² vs £80–£120/m² for GRP), and good cold-temperature performance. EPDM is our alternative recommendation where the specific substrate or geometry makes GRP installation impractical. For most standard Leicester rear extension and garage flat roofs, GRP is our first recommendation.
“Had three quotes for our rear extension flat roof — two recommended felt, one recommended GRP. Went with GRP on this company's advice and cost breakdown. Two years in, completely watertight.”
“Old felt on our garage roof replaced with GRP. They explained the cost comparison clearly and the GRP case was obvious. Done in one day. Excellent finish.”
“GRP on our extension, felt had failed at three lap joints. Proper deck assessment done first, two rotten boards replaced, GRP laid. Done correctly from the start.”
EPDM rubber has the longest published design life at 30–50 years, followed by GRP fibreglass at 25–40+ years. Both significantly outlast 3-layer felt at 10–20 years. In Leicester's climate, we see GRP installations from the late 1990s still performing correctly where the installation was done to the right specification — over 25 years of field performance.
Yes, with conditions. The existing deck must be structurally sound and dry. We carry out a moisture survey with a damp meter before specifying GRP over existing felt. Where deck moisture levels are elevated, the felt must be stripped and the deck allowed to dry or replaced before GRP application. Installing GRP over wet felt traps moisture and causes premature deck failure — we do not do this.
Neither system should be installed in frost or near-freezing conditions. Both GRP and mineral felt require temperatures above 5°C for correct cure or adhesion. EPDM has a lower temperature threshold and can be installed in cooler conditions. Summer and early autumn are the optimal installation periods for all flat roof systems in Leicester.
Repair is appropriate for isolated failures on a system with remaining design life. Full replacement is appropriate when: the system is past design life; there are multiple failure points across the roof; the deck has widespread moisture damage; or the existing system is incompatible with effective repair (old felt with delaminated laps throughout). A free survey determines which applies to your specific roof.
Yes. Part L of Building Regulations requires flat roof replacements to include insulation to a minimum U-value of 0.18 W/m²K. This is typically achieved with 100–150mm of PIR rigid insulation in a warm roof configuration. We include Building Regulations compliant insulation in all flat roof replacement quotes as standard.
GRP: 25–40+ years. 3-layer felt: 10–20 years. Over 40 years, one GRP installation typically costs less in total than two felt replacements, before accounting for disruption and consequential damage from felt failure.
GRP cannot be installed below 5°C, restricting it to approximately March–November in Leicester. For urgent flat roof replacement in Leicester autumn and winter, EPDM rubber with its lower temperature threshold is our recommended alternative.
GRP for a garage in sound structural condition — 25–40 year design life, minimal maintenance. EPDM where the deck is irregular or installation is in cooler months. Both are significant upgrades over felt.
We cover all of Leicester city and the surrounding Leicestershire area. Free surveys with no call-out fee, written condition report within 48 hours of the visit. We have been working across Leicester and Leicestershire since 2003, carrying out repairs, re-roofing, flat roofing, lead work, chimney work and emergency call-outs across all property types and all LE postcodes.
NFRC registered (verifiable at nfrc.co.uk), £5m public liability insurance, 10-year written workmanship guarantee on all re-roofing work. No work starts without your written acceptance of the written itemised quote. Call 0116 319 1348 Monday–Friday 8am–6pm or Saturday 8am–2pm. Emergency line 24/7.
Every job starts with a free on-site survey. The written quote follows within 48 hours and specifies every element: scope of work, materials by manufacturer name, access method, guarantee period and payment terms. There are no verbal quotes, no time-pressure acceptance conditions, and no costs added on site without your prior written agreement. This is the standard we have operated to since 2003 and the standard we will continue to operate to. If you have had a poor experience with a Leicester roofer in the past, we would welcome the opportunity to demonstrate what transparent, professional roofing practice looks like.
No call-out fees. No obligation. Written quote within 48 hours. Covering all of Leicester and Leicestershire.
0116 319 1348 ✉ Email Us