EPDM vs GRP vs Felt: Which Flat Roofing Material Is Best?

If you’re replacing a flat roof on an extension, garage, dormer or other part of your property, you’ll probably come across three common options: EPDM rubber, GRP fibreglass and felt roofing.

But which one is best?

The answer depends on your budget, the type of property, how the roof will be used and how long you want the roofing system to last.

Current UK roofing guides commonly place modern felt at the lower end of the cost range, with EPDM and GRP generally costing more but offering longer expected service lives. Exact lifespan and price vary considerably with specification and installation quality.

EPDM vs GRP vs Felt at a Glance

These are broad industry guide ranges rather than guaranteed lifespans or quotations. Installation quality, roof design, drainage and maintenance can have a major effect on performance.

What Is EPDM Flat Roofing?

EPDM stands for ethylene propylene diene monomer and is a synthetic rubber roofing membrane.

It is supplied as a flexible sheet and can often cover a domestic flat roof with very few joints.

That makes EPDM a popular option for:

• House extensions
• Garages
• Dormers
• Porches
• Small commercial roofs
• Domestic flat roof replacements

One of its biggest advantages is flexibility.

A properly installed EPDM system can accommodate some movement in the building without becoming as brittle as some older roofing materials.

Advantages of EPDM

• Long potential service life
• Flexible material
• Low maintenance
• Good resistance to weather and UV exposure
• Few joints on many domestic roofs
• Suitable for many extensions and garages

Potential disadvantages

• Can be punctured by sharp objects
• Edges and roof details need careful installation
• Incorrect adhesive or detailing can cause failures
• Generally costs more upfront than basic felt

Some current UK guides estimate EPDM at around 25–50 years, depending on specification and installation.

What Is GRP Flat Roofing?

GRP stands for glass-reinforced plastic, commonly called fibreglass.

GRP roofing is created using fibreglass reinforcement and resin to form a hard, waterproof surface.

Unlike a flexible rubber membrane, GRP cures into a rigid finish.

It can be particularly useful where a homeowner wants a durable surface that can tolerate occasional foot traffic.

Advantages of GRP

• Hard and durable surface
• Seamless finish when correctly installed
• Suitable for complex roof shapes
• Can be designed with different finishes
• Good option for some balconies and walkable roofs
• Relatively low maintenance

Potential disadvantages

• Usually more expensive than basic felt
• Installation requires appropriate skill
• Resin needs suitable conditions to cure properly
• Rigid systems need appropriate roof construction and detailing

GRP is commonly quoted with a service life of roughly 25–30 years or more, depending on the system and installation.

What Is Felt Flat Roofing?

Felt is a traditional and widely used flat roofing material.

Modern built-up felt systems can still provide a practical roofing solution when correctly specified and installed.

It is particularly common on:

• Garages
• Sheds
• Workshops
• Outbuildings
• Smaller flat roofs
• Budget-conscious projects

Advantages of Felt

• Lower initial cost
• Widely available
• Established roofing system
• Relatively straightforward to repair
• Suitable for many smaller flat roofs

Potential disadvantages

• Generally shorter lifespan than EPDM
• Seams and laps can become vulnerable over time
• Can blister, crack or deteriorate
• May require more maintenance as it ages

Current UK guides generally place modern felt below EPDM and GRP in expected service life, although the exact lifespan depends heavily on the particular system and workmanship.

EPDM vs GRP: Which Is Better?

There isn’t one universal winner.

Choose EPDM if:

• You want a long-lasting flexible membrane
• You’re roofing an extension or garage
• You want relatively low maintenance
• The roof isn’t intended to be a regular walkway
• You want fewer joints on a straightforward roof

Choose GRP if:

• You want a hard surface
• The roof may receive occasional foot traffic
• Appearance is important
• The roof has complex details
• You’re considering a balcony or walkable roof

GRP and EPDM can both be excellent systems when correctly specified and installed. The better option depends on the roof design rather than simply choosing the material with the longest advertised lifespan.

EPDM vs Felt: Which Should You Choose?

The main difference is often upfront cost versus expected lifespan.

Felt generally offers a lower initial price.

EPDM usually costs more but can offer a considerably longer service life.

If you’re replacing a small garage roof and your main priority is keeping the initial cost down, felt may make sense.

If you’re replacing a flat roof on a home extension and want a longer-term solution, EPDM may be worth considering.

Your roofer should also assess the existing roof structure before recommending a system.

GRP vs Felt: Which Is Better?

GRP generally provides a more durable and rigid finish than traditional felt.

Felt can make sense where budget is the primary consideration.

GRP may be more suitable when:

• The roof is visible
• Durability is a priority
• The surface may receive foot traffic
• You want a hard finished surface
• The roof has complicated detailing

However, paying more for GRP doesn’t automatically make it the right choice.

The roof deck, drainage, insulation, falls and installation quality all matter.

Which Flat Roof Material Lasts the Longest?

Among the three common systems, EPDM is frequently quoted with the longest potential service life, with some current UK guides giving ranges of around 30–50 years.

GRP is commonly placed around 25–30+ years.

Modern felt is generally shorter-lived, often around 15–25 years depending on the system and installation.

However, these numbers should not be treated as guarantees.

A poorly installed long-life membrane can fail earlier than a correctly installed lower-cost system.

Which Flat Roof Is Cheapest?

In most comparisons, felt is the cheapest of the three for initial installation.

EPDM usually sits in the middle, while GRP can be more expensive depending on the roof and specification.

Current 2026 UK guides show broad installed price ranges that vary substantially between suppliers and regions, so homeowners should use them only for initial budgeting rather than treating them as fixed market prices.

The cheapest option isn’t always the cheapest over the lifetime of the roof.

For example, replacing a lower-cost roof several times can ultimately cost more than installing a longer-lasting system once.

Does Flat Roof Installation Quality Matter?

Yes.

In fact, installation quality can be just as important as the membrane itself.

Problems can occur when a roof has:

• Poor drainage
• Incorrect falls
• Badly installed edges
• Poorly sealed joints
• Incorrect flashing
• Damaged roof decking
• Inadequate detailing around outlets
• Poor preparation

Industry comparisons consistently emphasise that the material alone doesn’t determine how long a flat roof will last.

A good roofing contractor should assess the complete roof system rather than simply selling you a particular membrane.

What About Flat Roof Insulation?

If you’re replacing a flat roof over a habitable part of your home, don’t focus only on the waterproofing membrane.

The roof construction and insulation specification are also important.

A warm roof places insulation above the roof deck and can improve thermal performance while reducing condensation risks when correctly designed.

Depending on the property and project, upgrading insulation may also form part of the wider roof replacement.

Your roofing contractor should explain the proposed build-up rather than quoting only for the outer membrane.

How Much Does a Flat Roof Cost?

Flat roofing prices vary according to:

• Roof size
• Existing roof condition
• Material
• Insulation
• Roof deck
• Access
• Edge details
• Drainage
• Labour
• Removal of existing materials

Current 2026 UK guides give very different price ranges because projects can have very different specifications. For example, one current comparison gives approximate fitted ranges of £70–£120/m² for felt, £90–£150/m² for EPDM and £100–£160/m² for GRP, while other guides report lower figures for simpler installations.

This is why a site-specific quotation is much more useful than relying on an online average.

What Is the Best Flat Roof for a Garage?

For a garage, several options can work.

EPDM

A strong option if you want a long-lasting, low-maintenance roof.

GRP

Useful when you want a hard, durable surface and the roof may receive occasional foot traffic.

Felt

A practical choice when keeping the initial project cost lower is important.

The best option depends on your garage, existing roof structure, budget and expected lifespan.

What Is the Best Flat Roof for an Extension?

For many domestic extensions, EPDM is a popular option because of its flexibility, relatively low maintenance and potential long service life.

GRP can also be suitable, particularly where a hard finish or more complex detailing is required.

Felt can still be appropriate for certain projects where budget is the main consideration.

There is no single material that is right for every extension.

Should You Repair or Replace Your Flat Roof?

Before choosing a new material, determine whether the existing roof actually needs replacing.

A repair may be sufficient when:

• Damage is localised
• The membrane is generally sound
• There are only minor leaks
• Flashing or edge details have failed
• A small section has been damaged

Replacement may be more appropriate when:

• The membrane has widespread deterioration
• Leaks are recurring
• There are multiple damaged areas
• The roof structure is affected
• Previous repairs have repeatedly failed
• The roof has reached the end of its useful life

A professional inspection can help establish whether repair or replacement makes more sense.

How to Choose the Right Flat Roofing Material

Before making a decision, consider these five questions:

1. What is your budget?

If upfront cost is the biggest concern, felt may be worth considering.

2. How long do you want the roof to last?

If long-term service life is important, EPDM or GRP may be worth considering.

3. Will anyone walk on the roof?

If regular or occasional foot traffic is expected, discuss whether GRP or another suitable system would be more appropriate.

4. What does the existing roof look like?

The roof deck, falls, drainage and existing structure can affect which system is suitable.

5. What does your roofer recommend?

A professional should explain why a particular system is suitable rather than simply recommending the most expensive option.

EPDM vs GRP vs Felt: The Simple Answer

If you want the shortest possible answer:

EPDM — often a strong all-round choice for extensions, garages and similar domestic flat roofs where longevity and low maintenance matter.

GRP — particularly useful where you want a hard, durable and potentially walkable finish or have more complex detailing.

Felt — often the budget-friendly option for suitable garages, outbuildings and projects where a lower initial cost is important.

None is automatically the “best” flat roof for every property.

The right choice depends on your roof, budget, intended use, installation method and expected lifespan.

Flat Roofing Services in Basingstoke

Smart Roofing LTD provides flat roofing services in Basingstoke, Lychpit and surrounding areas.

Our roofing services include:

• Flat roof installation
• Flat roof replacement
• Flat roof repairs
• Roof inspections
• Roof leak repairs
• Guttering and fascia services
• Chimney repairs
• New roof installation
• Emergency roofing services

If you’re unsure whether your flat roof needs repair or replacement, a professional assessment can help you understand the condition of the roof and which roofing system may be suitable.

Frequently Asked Questions

What is the best flat roofing material in the UK?

There isn’t one material that’s best for every property. EPDM is often chosen for its flexibility and long potential service life, GRP for its hard and walkable finish, and felt for its lower initial cost. The right choice depends on the roof and how it will be used.

Is EPDM better than felt?

EPDM can offer a longer expected service life than felt, but it generally costs more upfront. For homeowners prioritising longevity and low maintenance, EPDM can be an attractive option.

Is GRP better than EPDM?

Not necessarily. GRP can be preferable where a hard, walkable finish is required, while EPDM is often well suited to straightforward domestic roofs where flexibility and longevity are priorities.

How long does an EPDM flat roof last?

Depending on the system, installation and maintenance, current UK guides commonly quote around 25–50 years for EPDM. Actual performance depends heavily on installation quality and roof detailing.

How long does a felt flat roof last?

Modern felt roofing can provide many years of service, with current UK guides commonly giving approximately 15–25 years depending on the system, installation and maintenance.

Should I repair or replace my flat roof?

If the damage is isolated, repair may be sufficient. If the membrane is extensively deteriorated, leaks keep returning or the roof structure is affected, replacement may be worth considering.