Choosing a flat roof covering means weighing up options that all claim to do the same job. Rubber roofing, felt, and fibreglass each have advocates, and each has a place in the market. But which is genuinely best for your property?
The honest answer is: it depends. Your budget, how long you plan to own the property, what’s beneath the roof, and your tolerance for maintenance all influence the right choice. This guide cuts through the marketing claims to give you a straightforward comparison, helping you make an informed decision for your South Wales home or business.
The Three Main Contenders
Before comparing these materials, let’s establish what each actually is and how they work.
Rubber Roofing (EPDM)
Rubber roofing uses EPDM (ethylene propylene diene monomer), a synthetic rubber membrane. It comes in large sheets that bond to the roof deck using adhesive, creating a seamless waterproof covering. The material has been used since the 1960s and dominates the modern flat roof market.
EPDM remains flexible across temperature extremes, doesn’t degrade in wet conditions, and typically lasts 30 to 50 years with minimal maintenance.
Felt Roofing
Felt roofing consists of bitumen-coated layers, typically applied in two or three sheets with overlapping joints. Traditional felt uses a torch to melt the bitumen and bond layers together. Modern variants include self-adhesive and cold-applied options.
Felt has been the default flat roof choice for decades, familiar to most roofers and widely available. However, it has a shorter lifespan than modern alternatives.
Fibreglass Roofing (GRP)
Fibreglass—technically glass-reinforced polyester (GRP)—creates a rigid, seamless surface. Installation involves laying fibreglass matting into liquid resin, which cures to form a hard shell. The result is a solid, jointless covering.
GRP gained popularity as an upgrade from felt, offering better durability and a seamless finish. It’s been used on flat roofs since the 1970s.
Lifespan Comparison
How long each material lasts significantly affects its true value.
Rubber Roofing: 30–50 Years
Quality EPDM installations routinely last 30 to 50 years. Many exceed this—some original 1960s installations remain serviceable today. The material doesn’t degrade significantly over time; it’s usually edge details rather than the membrane itself that eventually need attention.
Felt Roofing: 10–15 Years
Standard felt roofing typically lasts 10 to 15 years before requiring replacement. High-quality torch-on felt may reach 20 years in favourable conditions, but this is optimistic rather than typical. South Wales’ wet climate tends to shorten felt lifespan compared to drier regions.
Fibreglass Roofing: 20–25 Years
GRP generally lasts 20 to 25 years. Some installations exceed this, particularly on stable structures with careful installation. However, fibreglass can develop problems earlier if the underlying structure moves or the installation was substandard.
The Verdict on Lifespan
Rubber roofing wins decisively on longevity. A single EPDM roof outlasts two or three felt installations and typically exceeds fibreglass lifespan by a significant margin.
Cost Comparison
Understanding the full cost picture requires looking beyond initial installation prices.
Upfront Costs
For a typical single garage roof (approximately 15–18 square metres):
Felt: £400–£700 installed Fibreglass: £700–£1,200 installed Rubber roofing: £750–£1,400 installed
Felt costs least upfront. Fibreglass and rubber roofing have similar initial costs, though fibreglass can be slightly cheaper for simple installations.
Lifetime Costs
The calculation changes dramatically when you factor in replacement cycles over 30 years:
Felt: Two to three replacements needed = £1,200–£2,100 total Fibreglass: One replacement likely needed = £1,400–£2,400 total Rubber roofing: No replacement needed = £750–£1,400 total
Rubber roofing, despite higher upfront cost, typically delivers the lowest lifetime expenditure.
Maintenance Costs
Felt requires periodic attention—resealing, recoating, and patch repairs as it ages. Budget £50–£150 annually for a felt roof approaching end of life.
Fibreglass needs occasional inspection and minor repairs if cracks develop. Costs are typically modest but unpredictable.
Rubber roofing requires essentially no maintenance beyond debris clearance. Ongoing costs are minimal to zero.
The Verdict on Cost
Felt wins on day-one cost only. For any ownership period exceeding 10–15 years, rubber roofing provides better value. Fibreglass sits in the middle—better than felt but typically more expensive than rubber roofing over the long term.
Performance in Welsh Weather
South Wales weather tests flat roofs thoroughly. How does each material cope?
Rainfall Performance
Rubber roofing excels in wet conditions. The membrane doesn’t absorb water, doesn’t degrade through moisture exposure, and provides reliable waterproofing regardless of rainfall intensity or duration. Homeowners in Merthyr Tydfil, Aberdare, and throughout the valleys—where rainfall is particularly heavy—benefit from this resilience.
Felt struggles with persistent moisture. The material can absorb water, and prolonged damp accelerates degradation. Overlapping joints are vulnerable to water penetration as the material ages. Welsh weather shortens felt lifespan compared to drier climates.
Fibreglass handles rain well when intact. The rigid surface sheds water effectively and doesn’t absorb moisture. However, any cracks allow water ingress, and GRP doesn’t self-heal.
Temperature Variation
Rubber roofing remains flexible across temperature extremes. It stretches and contracts with thermal cycling rather than cracking. This flexibility is crucial for South Wales properties facing freezing valley winters and warmer summer conditions.
Felt becomes brittle in cold weather and soft in heat. Thermal cycling stresses the material and its joints, contributing to eventual failure. Cold weather increases cracking risk; hot weather can cause blistering.
Fibreglass is rigid and doesn’t accommodate movement well. If the underlying structure expands, contracts, or settles, GRP can crack. These cracks may be minor initially but often worsen over time.
UV Exposure
Rubber roofing contains UV stabilisers that prevent sun damage. The material maintains its properties despite decades of exposure.
Felt degrades under UV exposure. The bitumen dries out, causing cracking and brittleness. Sun-exposed felt roofs typically fail faster than shaded ones.
Fibreglass has reasonable UV resistance when properly finished, though the topcoat may need refreshing over time to maintain protection.
The Verdict on Weather Performance
Rubber roofing handles South Wales weather most reliably. It’s the safest choice for properties facing challenging conditions. Fibreglass performs adequately when intact but cracks can develop. Felt is the weakest performer in our wet, variable climate.
Installation Considerations
How each material is installed affects both quality and practicality.
Rubber Roofing Installation
EPDM installation involves bonding the membrane to the deck using specialist adhesive. The process is relatively clean, produces no strong odours, and doesn’t involve naked flames. Large membrane sheets mean fewer joints and faster coverage.
Installation requires dry conditions and temperatures above 5°C for optimal adhesive performance. A typical garage roof takes one day; larger projects may take two to three days.
Felt Installation
Traditional torch-on felt requires open flames on the roof—a fire risk requiring careful management. Modern cold-applied variants avoid this but may have shorter lifespans.
Felt installation involves multiple layers with overlapping joints, creating more potential failure points. Installation is relatively quick but the multiple layers mean more labour than single-membrane systems.
Fibreglass Installation
GRP installation involves applying liquid resin and fibreglass matting, which cure to form the finished surface. The resin produces strong odours during application and curing.
Temperature sensitivity is significant—fibreglass cannot be installed in cold or damp conditions. This limits installation windows in South Wales, potentially delaying projects.
The cured surface is hard and durable but inflexible. Any movement in the underlying structure after installation can cause problems.
The Verdict on Installation
Rubber roofing offers the most straightforward installation—no flames, minimal odour, and reasonable temperature tolerance. Felt installation is familiar but involves fire risk with traditional methods. Fibreglass has the most restrictive installation conditions and strongest odours.
Maintenance Requirements
Ongoing maintenance affects both cost and convenience.
Rubber Roofing Maintenance
Virtually none required. Periodic debris clearance and occasional visual inspection are sufficient. There’s no recoating, no resealing, no regular treatment needed. Most homeowners check their rubber roof twice yearly and that’s the extent of maintenance.
Felt Maintenance
Regular attention extends felt lifespan but doesn’t prevent eventual replacement. Maintenance includes inspecting and resealing joints, checking for and repairing blisters, recoating with solar reflective paint, and clearing debris from drainage paths.
As felt ages, maintenance requirements increase. A roof that needed annual attention initially may need quarterly checks as it approaches end of life.
Fibreglass Maintenance
Moderate maintenance requirements. GRP needs periodic inspection for cracks and damage, occasional topcoat refreshment for UV protection, and prompt repair of any damage to prevent water ingress.
Maintenance is less intensive than felt but more than rubber roofing.
The Verdict on Maintenance
Rubber roofing wins decisively. If minimal maintenance appeals to you, EPDM is the clear choice. Felt requires the most ongoing attention; fibreglass sits between the two.
Suitability for Different Applications
Each material suits certain applications better than others.
Garage Roofs
Best choice: Rubber roofing
Garages often receive less attention than the main house. A low-maintenance covering that lasts decades without intervention suits these structures perfectly. Rubber roofing handles garage roofs excellently across South Wales.
Acceptable: Fibreglass
GRP works adequately on garage roofs, particularly on newer, stable structures.
Budget option: Felt
If budget is genuinely constrained and you accept shorter lifespan, felt provides basic coverage.
Extensions and Living Spaces
Best choice: Rubber roofing
When occupied space lies beneath the roof, reliability matters most. Water damage to interiors is expensive and disruptive. Rubber roofing’s excellent waterproofing track record makes it the safest choice for extensions.
Alternative: Fibreglass
GRP provides good protection when properly installed on stable structures.
Not recommended: Felt
The shorter lifespan and higher failure risk make felt a poor choice for extensions where leaks cause significant damage.
Porches and Bay Windows
Best choice: Rubber roofing
Small areas with complex detailing suit EPDM’s flexibility. The material can be dressed into awkward shapes and around features.
Alternative: Fibreglass
GRP works well on small areas and copes with moderate complexity.
Acceptable: Felt
Traditional approach for small areas, though modern alternatives offer better longevity.
Commercial Buildings
Best choice: Rubber roofing
Large commercial roofs benefit from EPDM’s scalability, longevity, and minimal maintenance requirements. Business disruption is minimised both during installation and throughout the roof’s life.
Alternative: Fibreglass
GRP suits some commercial applications, particularly where a hard-wearing surface is beneficial.
Rarely appropriate: Felt
Commercial buildings need reliable, long-lasting solutions. Felt’s shorter lifespan makes it a poor choice for most business premises.
Making the Right Choice for Your Property
Having compared all three materials, how do you decide which is right for your situation?
Choose Rubber Roofing If:
- You want the longest-lasting solution
- Low maintenance matters to you
- You plan to own the property for more than 10 years
- Reliability is more important than minimum upfront cost
- The space below is valuable (living areas, offices, stored contents)
- You want to solve the roofing problem once
For most property owners, rubber roofing represents the best overall choice. Its combination of longevity, performance, and low maintenance delivers the best value over time.
Choose Fibreglass If:
- You prefer a hard, rigid surface
- Aesthetics are important (colour options available)
- Your structure is stable with minimal movement
- You want an upgrade from felt but have moderate budget
- The installation window suits GRP (warm, dry conditions)
Fibreglass is a legitimate choice for specific situations, particularly where its characteristics align with your requirements.
Choose Felt If:
- Budget is genuinely your primary constraint
- You’re selling the property soon and need basic functionality
- You accept that replacement will be needed in 10–15 years
- The roof covers non-critical space where occasional leaks are tolerable
Felt has a role when circumstances genuinely constrain other options. Just understand what you’re accepting—shorter lifespan, more maintenance, and eventual replacement.
Common Questions Answered
Can I install any of these over my existing roof?
Rubber roofing can sometimes overlay existing coverings if the deck is sound and the surface reasonably flat.
Fibreglass generally requires stripping back to a solid deck—it can’t bridge uneven surfaces.
Felt can layer over existing felt but this builds up thickness and weight over time.
Professional assessment determines what’s possible for your specific roof.
Which handles foot traffic best?
Fibreglass provides the hardest surface for regular foot traffic.
Rubber roofing handles occasional access well; walkway pads protect high-traffic areas.
Felt is most vulnerable to foot traffic damage, especially in hot weather when the material softens.
What about appearance?
Felt appears as traditional black/grey flat roofing.
Fibreglass offers colour choices and a smooth, finished appearance.
Rubber roofing is typically black, though lighter colours exist. Most flat roofs aren’t visible from ground level, making appearance a non-issue.
Which is most environmentally friendly?
Rubber roofing ranks well—long lifespan means less replacement waste, and EPDM is recyclable.
Fibreglass has moderate environmental impact; long lifespan helps but the material isn’t easily recyclable.
Felt has the highest environmental impact due to frequent replacement and limited recycling options.
Our Recommendation
For most South Wales properties, rubber roofing is the best choice. It handles our climate reliably, lasts for decades, requires minimal maintenance, and provides the best lifetime value.
We’re not saying this because we prefer installing EPDM—we’re saying it because the evidence supports it. Sixty years of proven performance, superior weather handling, and genuinely low maintenance make rubber roofing the rational choice for most flat roof situations.
Fibreglass has its place for specific applications where its characteristics add value. Felt remains an option when budget truly prevents alternatives.
Get Expert Advice for Your Property
Still unsure which material suits your flat roof? The best approach is professional assessment. At M&J Roofing, we evaluate your specific situation—roof condition, structure, usage, budget—and recommend the most appropriate solution.
We install rubber roofing across South Wales because it’s typically the best choice, but we’ll tell you honestly if your situation favours an alternative.
Contact us to arrange a no-obligation survey. We’ll examine your roof, discuss your requirements, and provide clear guidance on the right material for your property.
Your flat roof deserves a covering that performs reliably for decades. Make an informed choice—and get it right first time.
