EPDM vs GRP vs Felt: Which Flat Roof Material Is Right for Your Sheffield Home?
Want a deeper dive on EPDM specifically? Our EPDM rubber roofing Sheffield guide covers installation detail, cost breakdown, and why it handles South Yorkshire winters better than felt.
If you have a flat roof on your garage, extension, bay window or outbuilding — and it needs replacing — you’ll probably come across three main material options: EPDM rubber, GRP fibreglass and traditional felt. Each has its strengths, its weaknesses, and a different price point.
Choosing the right material can mean the difference between a roof that lasts 50 years and one that needs attention again in a decade. This guide explains what each option actually is, what it costs in Sheffield, and what AJR Roofing tends to recommend based on the job in question.
EPDM Rubber Flat Roofs
EPDM stands for Ethylene Propylene Diene Monomer — a synthetic rubber membrane that’s been widely used in commercial flat roofing for decades and is increasingly popular for domestic properties.
EPDM is typically installed as a single continuous sheet, which means fewer joins and a significantly lower risk of water ingress compared to older felt systems.
Advantages of EPDM
- Long lifespan: A properly installed EPDM roof can last 40–50 years or more.
- Single membrane: Fewer seams means fewer potential failure points.
- Flexible: EPDM handles temperature fluctuations well — it expands and contracts without cracking.
- Lightweight: Less structural load than GRP, which can matter on older or lighter structures.
- Suitable for larger areas: EPDM sheets come in very large sizes, making it cost-effective for bigger roofs.
Disadvantages of EPDM
- Not as rigid as GRP — can be vulnerable to punctures from foot traffic or sharp objects
- Requires specialist adhesives and careful installation at edges and joins
- Less aesthetically common in the UK domestic market than GRP
Typical cost in Sheffield
EPDM flat roof installation in Sheffield typically costs between £70–£100 per square metre, including materials and labour. A standard garage roof of around 20m² would cost roughly £1,400–£2,000.
GRP Fibreglass Flat Roofs
GRP stands for Glass Reinforced Polyester — a rigid fibreglass system that’s applied in liquid form and cures to a hard, seamless surface. It’s the most popular flat roof choice for domestic properties in the UK over the past decade.
Advantages of GRP
- Completely seamless: Applied as a liquid, GRP bonds to the decking and cures into a continuous surface with no joins — excellent waterproofing performance.
- Very durable: A well-installed GRP roof typically lasts 25–40 years with minimal maintenance.
- Low maintenance: Resistant to algae growth and doesn’t require regular treatments.
- Can be walked on: GRP can withstand foot traffic once cured, making it suitable for accessible flat roofs.
- Neat finish: Clean edges and a professional appearance, with colour options available.
Disadvantages of GRP
- Higher material cost than felt and slightly more than EPDM in some cases
- Requires experienced installation — incorrect application can lead to cracking or adhesion failure
- Can be brittle in extreme cold if not applied correctly
- Heavier than EPDM — worth checking structural load capacity on older buildings
Typical cost in Sheffield
GRP flat roofing in Sheffield typically costs between £80–£120 per square metre installed. For a 20m² garage roof, expect to pay in the region of £1,600–£2,400.
Felt Flat Roofs
Traditional felt (bitumen felt) has been used on flat roofs for generations. Modern torch-on felt is a significant improvement over the old nailed-down layered systems, but it still has a shorter lifespan than EPDM or GRP.
Advantages of felt
- Lower upfront cost: Felt is generally the cheapest of the three options to install.
- Widely available: Any roofing contractor can work with it, and materials are readily sourced.
- Good for temporary solutions: If budget is the primary concern and a longer-term replacement is planned, felt can bridge the gap.
Disadvantages of felt
- Shorter lifespan: Modern torch-on felt typically lasts 10–20 years — significantly less than GRP or EPDM.
- More joins: Felt systems have multiple laps and seams, each a potential failure point.
- Requires regular maintenance: Felt can become brittle and crack over time, especially with exposure to UV.
- Higher long-term cost: Replacing a felt roof twice in the time a GRP roof would last once often makes felt more expensive overall.
Typical cost in Sheffield
Torch-on felt flat roofing in Sheffield typically costs between £50–£80 per square metre, making it the most affordable upfront option — though the total cost over time tells a different story.
Side-by-Side Comparison
| Feature | EPDM | GRP | Felt |
|---|---|---|---|
| Typical lifespan | 40–50 years | 25–40 years | 10–20 years |
| Approx. cost/m² (Sheffield) | £70–£100 | £80–£120 | £50–£80 |
| Seamless? | Yes (large sheets) | Yes (liquid-applied) | No (multiple laps) |
| Foot traffic | Limited | Yes | No |
| Maintenance | Very low | Very low | Regular checks needed |
| Best suited for | Larger areas | Most domestic roofs | Budget/temporary |
Which Flat Roof Material Should You Choose?
The right material depends on several factors — and there’s no single answer that applies to every roof.
You want the lowest-maintenance, longest-lasting option for a standard domestic flat roof. GRP is our most commonly installed material for Sheffield home extensions and garages.
You have a large or unusual flat roof, an older building where weight is a concern, or a commercial application. EPDM excels in flexibility and large-area coverage.
If you’re unsure which option is right for your property, AJR Roofing can assess your existing roof and give you a clear recommendation — without any obligation. Visit our Flat Roofs page for more details, or contact us to arrange a free quote.
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FAQs: Flat Roof Materials Sheffield
Which flat roof lasts the longest?
EPDM has the longest expected lifespan — 40–50 years when properly installed. GRP fibreglass is close behind at 25–40 years. Both significantly outlast traditional felt, which typically lasts 10–20 years.
Is GRP better than EPDM?
It depends on the application. GRP is rigid, seamless and ideal for most domestic flat roofs. EPDM is more flexible, lighter, and better suited to larger areas. Both are excellent long-term options — the right choice comes down to the specific roof, building and budget.
Can you put EPDM over felt?
In some cases, yes — but only if the existing decking is in sound condition. It’s generally better practice to remove the old felt and install over fresh decking, which ensures the new membrane bonds correctly.
How long does a GRP flat roof take to install?
A standard garage or extension roof (15–25m²) typically takes one to two days. The fibreglass laminate needs adequate curing time before the topcoat is applied.
Is a flat roof always going to leak eventually?
A well-installed, high-quality flat roof should not leak during its expected lifespan. Leaks are typically the result of poor installation, damage, or a roof that’s past its natural end of life. Modern GRP and EPDM systems are highly reliable when installed correctly.
Do you install all three types of flat roof in Sheffield?
Yes. AJR Roofing installs GRP fibreglass and EPDM flat roofs across Sheffield and South Yorkshire. We’ll recommend the best option for your specific property and budget. Call 07852 940350 to discuss your requirements.