TL;DR
- Rubber roofing (EPDM) is the best choice for most UK flat roofs—lasting 30–50 years with minimal maintenance
- Felt roofing costs less upfront but needs replacing every 10–15 years, making it more expensive over time
- Fibreglass (GRP) offers 20–25 years lifespan but can crack if buildings move
- UK weather (heavy rain, temperature variation) suits rubber roofing’s flexibility and water resistance
- Over 30 years, rubber roofing costs approximately 50% less than repeated felt installations
- For new installations and replacements, rubber roofing delivers the best long-term value
When researching flat roofing options, you’ll encounter terms like “felt,” “rubber,” “EPDM,” “GRP,” and “fibreglass.” Understanding what these mean—and which delivers the best value—helps you make an informed decision.
This guide compares the main flat roofing materials available in the UK, examining lifespan, cost, performance, and suitability for British weather. By the end, you’ll understand which option makes most sense for your property.
Understanding the Options
First, let’s clarify what these materials actually are.
Felt Roofing
What it is: Layers of bitumen-saturated fabric, typically applied using heat (torch-on felt) or as self-adhesive sheets. Traditional flat roofing that’s been used for decades.
Also known as: Built-up roofing, torch-on felt, bituminous felt, roofing felt.
How it’s installed: Multiple layers bonded together, typically requiring a gas torch to melt bitumen and create adhesion.
Rubber Roofing (EPDM)
What it is: EPDM (ethylene propylene diene monomer) is a synthetic rubber membrane. It comes in large sheets that bond to the roof deck using adhesive.
Also known as: Rubber roofing, EPDM, rubber membrane, synthetic rubber roofing.
How it’s installed: Single sheet (often covering the entire roof) bonded to the deck with specialist adhesive. No heat required.
Fibreglass Roofing (GRP)
What it is: Glass-reinforced polyester—layers of fibreglass matting saturated with liquid resin that cures to form a rigid, seamless shell.
Also known as: GRP, fibreglass, glass fibre roofing.
How it’s installed: Resin and matting applied in layers directly onto the deck, curing to form a solid surface.
Quick Comparison Summary
Before diving into details, here’s the overview:
| Factor | Felt | Rubber (EPDM) | Fibreglass (GRP) |
|---|---|---|---|
| Lifespan | 10–15 years | 30–50 years | 20–25 years |
| Upfront cost | Lowest | Medium | Medium-High |
| Lifetime cost | Highest | Lowest | Medium |
| Maintenance | Increasing | Minimal | Moderate |
| UK weather performance | Adequate | Excellent | Good |
| Installation complexity | Moderate | Low-Moderate | Moderate-High |
| Best for | Budget/temporary | Most applications | Specific situations |
Lifespan Comparison
How long each material actually lasts in UK conditions.
Felt Roofing Lifespan
Typical lifespan: 10–15 years
Factors affecting longevity:
- Quality of felt used (basic vs premium)
- Number of layers applied
- Installation quality
- Weather exposure
- Maintenance provided
Reality check: Many felt roofs fail earlier than expected, particularly budget installations. Heavy UK rainfall accelerates degradation.
End-of-life signs: Cracking, splitting, bald patches where surface granules have worn away, brittleness, lifting at seams.
Rubber Roofing Lifespan
Typical lifespan: 30–50 years
Factors affecting longevity:
- Membrane quality and thickness
- Installation quality
- Edge detail execution
- Basic maintenance provision
Reality check: EPDM has been in use since the 1960s, with many original installations still performing. The long lifespan is proven, not projected.
End-of-life signs: Rarely seen on quality installations. Eventually, flexibility may reduce and general wear becomes evident—typically after 35+ years.
Fibreglass Lifespan
Typical lifespan: 20–25 years
Factors affecting longevity:
- Resin quality
- Installation skill and conditions
- Building stability (movement causes cracks)
- UV exposure and topcoat condition
Reality check: GRP performs well on stable structures but is vulnerable to cracking if buildings settle or move. Topcoat may need refreshing before membrane replacement.
End-of-life signs: Cracking, delamination, surface degradation, water penetration.
Lifespan Verdict
Winner: Rubber (EPDM)—delivering 2–3 times the lifespan of felt and significantly outlasting fibreglass.
Cost Comparison
Understanding true costs requires looking beyond initial price.
Upfront Costs
For a typical 20m² garage roof:
| Material | Material Cost | Installation | Total |
|---|---|---|---|
| Basic felt | £200–£300 | £250–£400 | £450–£700 |
| Quality felt | £300–£400 | £300–£450 | £600–£850 |
| Rubber (EPDM) | £400–£550 | £450–£650 | £850–£1,200 |
| Fibreglass (GRP) | £450–£600 | £500–£700 | £950–£1,300 |
Upfront winner: Felt costs less initially.
Lifetime Costs (30-Year Comparison)
The same 20m² garage roof over 30 years:
Felt roofing:
- Initial installation: £600
- Repairs (years 5–10): £200
- Replacement (year 12): £650
- Repairs (years 15–22): £250
- Replacement (year 24): £700
- 30-year total: £2,400+
Rubber roofing:
- Initial installation: £1,050
- Minor maintenance: £100
- 30-year total: £1,150
Fibreglass:
- Initial installation: £1,150
- Topcoat refresh (year 15): £250
- Replacement (year 23): £1,200
- 30-year total: £2,600
Cost Per Year of Service
| Material | Total Cost | Years Service | Cost Per Year |
|---|---|---|---|
| Felt | £2,400 | 30 (multiple roofs) | £80 |
| Rubber | £1,150 | 30 | £38 |
| Fibreglass | £2,600 | 30 (with replacement) | £87 |
Lifetime cost winner: Rubber (EPDM)—costing approximately half of alternatives over its service life.
Performance in UK Weather
British weather presents specific challenges for flat roofing.
Rainfall Performance
The UK averages 1,150mm of rainfall annually, with South Wales often receiving more. Persistent wet conditions test flat roofing materials thoroughly.
Felt: Adequate when new, but prolonged wet exposure accelerates degradation. Seams and edges are vulnerable to persistent moisture.
Rubber (EPDM): Excellent. Completely impermeable and unaffected by constant moisture. Doesn’t absorb water or degrade from wet conditions.
Fibreglass: Good when intact. The seamless surface handles rain well, but any cracks allow water entry.
Rainfall winner: Rubber (EPDM)
Temperature Performance
UK temperatures range from occasional sub-zero winters to warm summer days. Daily and seasonal temperature cycling creates stress.
Felt: Becomes brittle in cold, soft in heat. Temperature cycling accelerates cracking and splitting over time.
Rubber (EPDM): Remains flexible from -40°C to over 100°C—far beyond UK temperature range. Handles cycling without stress.
Fibreglass: Rigid material that doesn’t accommodate movement well. Temperature-induced expansion and contraction can cause cracking.
Temperature winner: Rubber (EPDM)
UV Resistance
Even UK sunshine causes cumulative UV damage over years.
Felt: Poor UV resistance. Surface degrades, granules loosen, material becomes brittle. Solar reflective coatings help but need reapplication.
Rubber (EPDM): Excellent. Contains UV stabilisers providing decades of protection without additional coatings.
Fibreglass: Moderate. Topcoat provides UV protection but may need refreshing every 10–15 years.
UV winner: Rubber (EPDM)
Wind Resistance
Exposed locations experience significant wind loading.
Felt: Multiple layers and edge details can be vulnerable to wind uplift if not properly secured.
Rubber (EPDM): Properly bonded membrane resists wind well. Mechanical fixing available for exposed locations.
Fibreglass: Rigid surface handles wind once cured, though edges need proper protection.
Wind winner: All adequate when properly installed; rubber slightly ahead for flexibility.
Overall UK Weather Performance
Clear winner: Rubber (EPDM)—handles all UK weather conditions without degradation.
Installation Differences
How each material is installed affects quality, speed, and conditions required.
Felt Installation
Process: Torch-on application melts bitumen to bond layers. Multiple layers built up for waterproofing.
Conditions required: Dry weather essential. Moderate temperatures preferred.
Time required: 1–2 days for typical domestic roof.
Skill requirements: Experience with gas torch application. Fire safety awareness essential.
Risks: Fire risk during installation. Quality heavily dependent on installer skill.
Rubber (EPDM) Installation
Process: Adhesive applied to both deck and membrane. Membrane positioned, bonded, and rolled for full contact.
Conditions required: Dry weather. Temperature above 5°C. Moderate wind.
Time required: Often single day for domestic roofs.
Skill requirements: Training in EPDM techniques. Attention to detail for edges and penetrations.
Risks: Lower risk than felt (no flame). Quality dependent on adhesive application and detail work.
Fibreglass (GRP) Installation
Process: Resin and matting applied in layers. Topcoat added once cured.
Conditions required: Very weather-sensitive. Dry conditions essential. Temperature affects curing.
Time required: 1–3 days depending on size and weather.
Skill requirements: Experience with GRP application. Understanding of resin chemistry.
Risks: Strong odours during installation. Weather interruption can compromise quality. Installation defects harder to remedy.
Installation Comparison
| Factor | Felt | Rubber | Fibreglass |
|---|---|---|---|
| Weather sensitivity | Moderate | Low-Moderate | High |
| Fire risk | Yes | No | No |
| Odour | Moderate | Low | High |
| Speed | Moderate | Fast | Moderate-Slow |
| Error forgiveness | Low | Moderate | Low |
Installation winner: Rubber (EPDM)—faster, safer, less weather-sensitive.
Maintenance Requirements
Ongoing maintenance affects total ownership experience.
Felt Maintenance
Regular requirements:
- Debris clearance (twice yearly)
- Drainage checks
- Seam inspection
- Surface condition monitoring
As it ages:
- Solar reflective coating may extend life
- Patch repairs become more frequent
- Seam re-sealing may be needed
- Increasing attention required
Maintenance burden: Moderate initially, increasing with age.
Rubber (EPDM) Maintenance
Regular requirements:
- Debris clearance (twice yearly)
- Drainage checks
- Visual inspection
Over time:
- Minimal change in requirements
- Occasional detail checks
- Professional inspection every 5–10 years (optional)
Maintenance burden: Minimal throughout life.
Fibreglass Maintenance
Regular requirements:
- Debris clearance
- Drainage checks
- Crack inspection
- Topcoat condition monitoring
Over time:
- Topcoat may need refreshing (10–15 years)
- Crack repairs if building moves
- Surface condition monitoring
Maintenance burden: Moderate, with periodic attention needed.
Maintenance Comparison
| Material | Annual Time | Skill Required | Cost Over Life |
|---|---|---|---|
| Felt | 3–5 hours (increasing) | Basic to moderate | £200–£400 |
| Rubber | 1–2 hours | Basic | £50–£150 |
| Fibreglass | 2–3 hours | Basic to moderate | £150–£400 |
Maintenance winner: Rubber (EPDM)—minimal attention required throughout its life.
Suitability by Application
Different applications may favour different materials.
Garage Roofs
Best choice: Rubber (EPDM)
Why: Garages need reliable, low-maintenance protection. Rubber delivers decades of service without attention. The cost difference versus felt is modest; the lifespan difference is dramatic.
Extension Roofs
Best choice: Rubber (EPDM)
Why: Extensions protect living space. Failure means interior damage. Long lifespan and reliability are essential. Building regulations favour quality insulated construction that EPDM complements.
Porch Roofs
Best choice: Rubber (EPDM)
Why: Small areas where proportionally, material cost matters less than labour. Quality rubber ensures decades without attention.
Dormer Roofs
Best choice: Rubber (EPDM)
Why: Exposed location at roof level demands materials handling severe weather. Must match main roof lifespan. Access difficulty makes maintenance undesirable.
Commercial Buildings
Best choice: Rubber (EPDM)
Why: Business continuity requires reliability. Large areas benefit from EPDM’s efficiency. Minimal maintenance suits commercial priorities.
Temporary Structures
Possible exception: Basic felt
Why: If genuinely temporary (under 10 years), felt’s lower upfront cost may be acceptable. However, even here, rubber’s minimal additional cost delivers far better value if the structure lasts.
Regional Considerations: South Wales
Local conditions affect material performance.
South Wales Weather
Rainfall: Above UK average in many areas. Valley locations particularly wet. Favours materials handling persistent moisture—rubber excels.
Temperature: Valley properties experience colder winters than coastal areas. Temperature cycling stresses felt; rubber handles it effortlessly.
Coastal exposure: Salt air affects some materials. Rubber’s chemical resistance handles coastal conditions well.
Local Recommendations
Throughout South Wales—whether in Cardiff, Swansea, Merthyr Tydfil, Aberdare, or surrounding areas—rubber roofing handles local conditions reliably.
Our regional climate makes EPDM’s weather resistance particularly valuable. Properties in wetter valleys especially benefit from materials unaffected by persistent moisture.
Common Questions Answered
Is rubber roofing worth the extra cost?
Yes, decisively. The upfront cost difference is typically £300–£500 for a garage roof. The lifespan difference is 20–35 years. Over the roof’s life, rubber costs less than half of felt alternatives.
Can I put rubber roofing over existing felt?
Sometimes, but not recommended. If felt is failing, underlying issues (deck damage, moisture) need addressing. Overlay hides problems rather than solving them. Full replacement with deck inspection is better practice.
Is fibreglass better than rubber?
Generally no. Fibreglass offers good performance on stable structures but:
- Shorter lifespan (20–25 vs 30–50 years)
- Cracking risk if building moves
- More weather-sensitive installation
- Higher maintenance requirements
Fibreglass may suit specific situations (colour requirements, particular hard surfaces), but rubber delivers better all-round performance.
How do I know if my felt roof needs replacing?
Signs indicating replacement:
- Cracking or splitting visible
- Bald patches where surface has worn
- Multiple repair patches
- Persistent leaks despite repairs
- Roof is 12+ years old with deterioration
Can I install rubber roofing myself?
DIY is possible for small, simple roofs if you:
- Research thoroughly
- Use proper products
- Follow manufacturer guidance
- Accept no warranty protection
For most homeowners, professional installation ensures proper execution, compliance, and warranty coverage.
Does rubber roofing work in winter?
Yes. EPDM remains flexible down to -40°C—far below any UK temperature. Installation can proceed in temperatures above 5°C. Winter installation is feasible during appropriate weather windows.
Making Your Decision
Choose Felt If:
- Budget is severely constrained
- The structure is genuinely temporary
- You accept replacing the roof in 10–15 years
- Lower upfront cost outweighs higher lifetime cost
Choose Rubber (EPDM) If:
- You want the best long-term value
- The roof protects valuable property or living space
- You prefer minimal maintenance
- You want the roof lasting 30+ years
- UK weather performance matters
Choose Fibreglass If:
- Colour matching is essential
- The building is very stable (no movement)
- You specifically want a hard surface
- Local installer expertise favours GRP
For Most Situations
Rubber (EPDM) is the clear winner. It delivers:
- Longest lifespan
- Best UK weather performance
- Lowest lifetime cost
- Minimal maintenance
- Proven reliability
The modest additional upfront investment delivers dramatically better outcomes.
Summary: The Clear Winner for UK Flat Roofing
Comparing felt, rubber, and fibreglass for UK flat roofing:
Felt offers the lowest upfront cost but shortest lifespan, highest lifetime cost, and poorest weather performance. Suitable only for severely budget-constrained or genuinely temporary applications.
Fibreglass provides moderate performance but with cracking risks, weather-sensitive installation, and shorter lifespan than rubber. Has specific niche applications but isn’t the best general choice.
Rubber (EPDM) delivers the longest lifespan, lowest lifetime cost, best weather performance, and minimal maintenance. It’s the clear choice for most UK flat roofing applications.
For South Wales properties facing our wet climate, rubber roofing’s impermeability and weather resistance make it particularly appropriate. The additional upfront investment versus felt is typically recovered within 10–15 years—then you enjoy 20–35 more years of service.
Quality Flat Roofing Across South Wales
At M&J Roofing, we recommend and install rubber (EPDM) flat roofing as the best solution for most applications. We’ve seen the long-term outcomes of different materials and consistently find EPDM delivering the best results.
Contact us to discuss your flat roofing requirements. We’ll explain your options honestly, provide clear quotations, and deliver quality installation that serves you reliably for decades.
