Is a Rubber Roof Better Than Felt or Fibreglass?

Rubber is often better than felt because it usually has few or no seams and tends to last longer, but fibreglass can be a tougher choice for roofs you walk on. The right material depends on your budget, the size of your roof and what you use it for.

The three main flat roof coverings

When flat roof quotes arrive, you will usually see three main options. These are built-up felt, EPDM rubber and GRP fibreglass. For many years, felt was the standard choice for a domestic flat roof. Today, rubber and fibreglass are common alternatives that are often expected to last longer.

You might also see quotes for single-ply membranes or liquid coatings. Single-ply is a flexible sheet similar to rubber, while liquid systems are painted on to form a seamless waterproof layer. However, felt, rubber and fibreglass are the materials most local roofers fit every day.

Each covering sits on top of a timber deck. The deck is the structural wooden base of your flat roof, usually made of thick plywood or oriented strand board. The waterproofing layer goes over this deck to keep the rain out.

A good roofer will also check the roofline while they are up there. This includes the fascias, soffits and guttering. The fascia is the long board that carries the guttering, and the soffit is the board tucked underneath it.

Rubber roofing explained

EPDM rubber roofing is a synthetic rubber membrane. It is supplied in large rolls and glued down to the timber deck. EPDM stands for ethylene propylene diene monomer, which is just the chemical name for this specific type of rubber.

The biggest advantage of a rubber roof is that it often comes in a single piece. For most domestic extensions or garages, a roofer can order a sheet cut to the exact size of the roof. This means there are no seams or joints across the main flat area. Seams and joints are a common place for a flat roof to leak.

Rubber is highly flexible, so it handles the natural expansion and contraction of your home during hot and cold weather. It also stands up well to sunlight, which helps it resist cracking over time.

The main limit roofers cite is how it looks. It has a plain, dark grey, industrial finish that not everyone likes if the roof is visible from an upstairs window. It can also be punctured by sharp objects, so it is not the best choice if you plan to put a balcony on it or walk on it regularly.

Felt roofing explained

Felt roofing has moved on significantly from the materials used decades ago. Modern felt is usually a built-up system made of two or three layers. These layers are rolled out over the timber deck and melted together using a blowtorch, which is why it is commonly called torch-on felt.

The top layer includes a mineral finish to protect the bitumen underneath from the sun. Felt remains the most familiar option for UK homes. It is a proven material that is usually the cheapest to buy and fit.

Because it comes in narrow rolls, a felt roof will always have seams. The installer has to overlap the edges and seal them perfectly with the torch. If this detailing is poor, water will eventually find its way in.

Felt is also less flexible than rubber. Over many years of baking in the summer and freezing in the winter, the material can become brittle. When it loses its flexibility, cracks appear and repairs are needed.

Fibreglass roofing explained

Fibreglass roofing is known in the trade as GRP, which stands for glass reinforced plastic. It is built by laying a mat of glass fibres over the timber deck and painting it with a liquid resin. Once the resin cures, a coloured topcoat is added to protect it.

The result is a completely rigid, seamless plastic shell over your roof. Because it is mixed and applied wet, it forms perfectly around tricky shapes like skylights or pipes. There are no joints to peel apart.

Fibreglass is incredibly tough. It cannot easily be punctured or sliced. Roofers often suggest it for a roof that has to take regular foot traffic. Leave any access to the roof to a professional, and treat turning a flat roof into a terrace or balcony as a separate project that needs its own structural and planning checks.

The drawback is its rigidity. Buildings move slightly as temperatures change. If a fibreglass roof is too large, it cannot flex enough to absorb this movement and can crack. Roofers usually recommend fibreglass for smaller roofs, or they will build expansion joints into larger ones to stop this happening.

How the costs compare

The price you pay depends heavily on the material you choose. Felt is generally the most affordable, followed by rubber, with fibreglass usually being the most expensive.

This table shows how the different materials compare on price per square metre.

These figures are typical published prices for 2026. Local quotes will differ based on where you live, how easy it is to access your roof and whether you need scaffolding. Prices are generally higher in London and the South East.

Remember that the material is only part of the bill. According to the Federation of Master Builders, labour is around 40 per cent of the cost of a replacement roof. If a quote looks unusually cheap, it is wise to ask why. The Federation advises homeowners to get a written itemised quote and be wary of rock-bottom prices.

Nobody can see rotten timber until the old covering is off. A good quote always states how extra timber work will be priced if the deck needs replacing.

How long each one lasts

The cheapest roof to install is rarely the cheapest roof over its lifetime. A well-maintained flat roof can last over 20 years, and some coverings are expected to last longer than others.

This table shows the expected lifespan for each type of flat roof covering.

These lifespans are typical published estimates for 2026. How long your roof actually survives depends on the weather, how well it drains and the skill of the person who fitted it.

Felt has the shortest expected lifespan at the bottom of its range, but the published ranges overlap, so treat them as a guide and not a promise. Rubber offers a strong middle ground, combining a long life with a reasonable installation price.

Which suits your roof?

There is no single best material for every flat roof. The right choice depends on what your roof has to do and how much you want to spend today.

If you are on a strict budget and need to make a garage or shed watertight quickly, built-up felt makes sense. It keeps the initial cost down while still offering a reliable waterproof layer for a decade or more.

If you want a low-maintenance covering for a standard extension, EPDM rubber is a strong choice. Few or no seams means fewer places to leak, and the price is reasonable for its expected lifespan.

If your roof has lots of awkward shapes, skylights or pipes, or if it has to take foot traffic, fibreglass is often the better option. It is tough, forms around details perfectly and creates a smart, clean finish.

Before you decide, it helps to understand how much a flat roof replacement costs in total, including the timber work and waste removal. Being sold a whole new roof for a local fault is a common scam, so always ask if a smaller fix is possible first.

Insulation and the rules that apply to all three

Whichever material you pick, replacing a flat roof is not just about keeping the rain out. You also have to follow building regulations.

The rules treat a roof as a thermal element. The Planning Portal states that work to re-cover a roof should include improving its insulation. If a flat roof with integral insulation is replaced, you may be required to upgrade it to meet modern energy standards.

A cold roof has insulation packed between the wooden joists. A warm roof has rigid insulation boards laid above the timber deck, immediately under the waterproof covering. Upgrading to warm roof insulation typically adds £15 to £35 per square metre to your quote.

You also need a formal building control application in certain situations. In England, repairing or re-covering a roof does not normally need a building control application if less than 25 per cent of the building envelope and less than 50 per cent of the roof is affected. Approval is required where 50 per cent or more of the roof is affected, where the new covering performs significantly differently in a fire, or where it increases the weight of the covering by 15 per cent or more.

A roofer registered with CompetentRoofer can self-certify this work in England and Wales. Otherwise, you must apply to your local council building control or a registered building control approver.

Rules differ in Scotland and Northern Ireland. If you live there, check with your local council before any work begins. Do not let a roofer tell you to ignore the paperwork, as a buyer's solicitor is likely to ask for the compliance certificate when you come to sell your house.

Why the installer matters more than the material

A premium fibreglass roof fitted badly will leak faster than a cheap felt roof fitted perfectly. The material is only as good as the tradesperson installing it.

Flat roofs are not actually flat. They must be built with a slight slope, known as a fall, so rainwater runs off into the guttering. If the timber deck is completely level or sags in the middle, water will sit in puddles on the roof. Standing water will eventually degrade felt and find its way through any weak seams in rubber.

Detailing is another area where bad roofers cut corners. The edges of the roof must be finished properly with trims, and the junction where the flat roof meets a brick wall must be sealed. This is usually done with lead flashing, which is tucked into the brickwork and dressed down over the roof covering.

If the flashing is loose or missing, water will run down the wall and behind your new roof. When comparing quotes, look for roofers who explain exactly how they will handle falls, trims and flashing.

If you are unsure how to choose a roofing company you can trust, look for membership of TrustMark. This is the government-endorsed quality scheme for work in and around the home. Membership is a good sign, though it is not a guarantee.

Questions to ask your roofer

When a roofer comes to look at the job, they should be happy to answer your questions. Getting the details clear early stops arguments later.

Use this checklist to structure your conversation:

• Are scaffolding, waste removal and VAT included in this price?
• Will you inspect the timber deck, and how much will it cost per square metre to replace any rotten boards?
• Does this quote include upgrading the insulation to a warm roof?
• Are you registered with a competent person scheme to sign off the building regulations?
• Is the new covering much heavier or different in fire performance than the old one?
• Do you provide an insurance-backed guarantee that protects me if your firm closes down?

Never accept a vague one-line quote. A proper quote is a fixed price, whereas an estimate can change. Under the Consumer Rights Act 2015, work must be done with reasonable care and skill, and if it is not you can ask for it to be put right or for money back.

Contracts agreed at home, by phone or online normally carry a 14-day cooling-off period. However, if you ask for work to start inside that period, you must pay for what has been done. Paying by credit card gives Section 75 protection on purchases over £100 and up to £30,000.

Be very wary of cold callers who have spotted moss or a loose edge from the street. They often pressure you to decide today, ask for cash only, demand big deposits and provide no physical address. Treat roof coating claims with caution and avoid pressure washing sold as maintenance, which can damage a roof. If a dispute arises, Citizens Advice is the place to go for help.

Common questions

Can you put rubber roofing over an old felt roof?

A new covering can sometimes be laid over an old one, but many roofers prefer to strip the roof first. Covering an old, wet roof can trap moisture that rots the timber deck. Stripping the old felt away is the only way to check the boards underneath are solid.

Is EPDM better than GRP fibreglass?

Neither is strictly better, as they suit different jobs. EPDM is highly flexible, comes in one piece and handles building movement well, making it ideal for standard flat roofs. GRP fibreglass is completely rigid and highly resistant to punctures, making it better for complex shapes or roofs you intend to walk on.

How much does a rubber flat roof cost?

Fitting an EPDM rubber roof typically costs between £80 and £120 per square metre. Published figures do not all include the same things, so ask whether each quote covers scaffolding, stripping the old roof, replacing any rotten timber and upgrading the insulation.

Why do flat roofs fail?

Flat roofs usually fail due to poor installation, a lack of slope for drainage or natural weathering over time. Sun damage makes old felt brittle, while standing water exploits poorly sealed seams. If you spot damp patches on your ceiling, roof repair costs will depend on whether the water has reached the timber deck.

Next steps

Choosing between rubber, felt and fibreglass is much easier once you know what your roof needs. Take your time, compare your options and do not let anyone pressure you into deciding today.

To get the best result for your home, follow these steps:

• Decide if your roof needs to handle foot traffic, which points towards fibreglass.
• Take photos of the defect from the ground or inside the loft to show roofers what is happening.
• Get three written, itemised quotes from local roofing firms.
• Check the quotes include removing the old covering and dealing with the building regulations.
• Ask to see proof of their public liability insurance before they start.
• Agree a staged payment plan and only pay the final balance when the job is completely finished.

If you are ready to get quotes and compare materials in person, you can find a roofer near you to inspect your flat roof and explain your options.