what is the best material for a flat roof uk
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Choosing the best material for a flat roof in the UK is one of the most important decisions you can make when building or renovating a garage, extension, outbuilding, or commercial space. Flat roofs have different performance needs compared to pitched roofs because they are more vulnerable to pooling water, UV damage, heavy rainfall, frost, and general wear. The right roofing material must be durable, weather resistant, cost effective, and suited to the structure beneath it.
This guide explains the most common flat roofing materials used across the UK and compares their lifespan, cost, installation method, maintenance needs, and suitability for different types of buildings. You will learn how materials like EPDM, GRP, felt, liquid systems, and PVC membranes perform in real world conditions. You will also find advice on which material is best for garages, garden offices, extensions, and commercial roofs. By the end you will know exactly what the best materials are for different scenarios and how to choose the right one for your project.
What makes a good flat roof material in the UK
Flat roof materials must meet specific performance expectations to withstand the UK climate. The best systems share several important characteristics.
Waterproofing ability
Flat roofs cannot rely on steep slopes to shed water. The roofing material must therefore create a fully sealed membrane that prevents pooling water from penetrating.
UV resistance
The UK experiences constant changes in weather including strong sunlight in summer. Good flat roof materials must resist UV degradation.
Flexibility in cold weather
Materials must cope with thermal expansion and contraction without cracking.
Strength against foot traffic
Many flat roofs need occasional maintenance or access. The chosen material should withstand occasional light foot traffic without damage.
Long lifespan and low maintenance
A good flat roof material should remain durable for many years with minimal ongoing maintenance.
Overview of the main flat roof materials used in the UK
Five main materials dominate the UK flat roofing market:
• EPDM rubber
• GRP fibreglass
• Torch on felt roofing
• Liquid applied roofing systems
• Single ply PVC or TPO membranes
Each has distinct strengths and drawbacks. The best choice depends on your budget, roof size, building use, and the installation skill available.
EPDM rubber roofing
EPDM is one of the most popular modern flat roof materials in the UK. It is a synthetic rubber membrane supplied in large seamless sheets.
Key advantages
Long lifespan
EPDM roofs typically last 20 to 30 years and often longer with proper installation.
No seams on small roofs
Most domestic garages and extensions can be covered with a single sheet which means fewer weak points.
Strong weather resistance
EPDM handles UV exposure, frost, and heat very well.
Low maintenance
It requires very little upkeep other than keeping debris clear.
Fast installation
Sheets are glued down which makes installation quick and simple for trained installers.
Disadvantages
• Vulnerable to punctures from sharp objects
• Must be installed with correct adhesives
• Edges need careful detailing to prevent wind uplift
• Appearance is plain and industrial
Best for:
• Garages
• Garden offices
• Small extensions
• New builds seeking longevity
EPDM is often considered one of the best all round materials for smaller domestic roofs due to its lifespan and reliable waterproofing.
GRP fibreglass roofing
GRP stands for glass reinforced plastic. It is a hard wearing roofing system formed using resin, fibreglass matting, and a coloured topcoat.
Key advantages
Excellent strength
GRP forms a rigid, fully bonded, seamless shell that is resistant to impact and foot traffic.
Long lifespan
A well installed GRP roof can last 20 to 30 years or more.
Attractive finish
The topcoat gives a clean, modern appearance available in several colours.
Ideal for complex shapes
GRP can be moulded around edges and corners which makes it suitable for roofs with multiple upstands.
Disadvantages
• Requires dry weather for installation
• Incorrect installation can lead to cracking
• Not ideal for very large roofs because GRP expands and contracts
• Can be expensive compared to felt
Best for:
• Garden rooms
• Small extensions
• Porches
• Domestic roofs needing a neat finish
GRP is widely regarded as the best material for small to medium sized flat roofs where appearance and durability are both important.
Torch on felt roofing
Felt roofing has been used in the UK for decades. Modern felt systems are far superior to older versions because they use polyester reinforced bitumen applied with heat.
Key advantages
Cost effective
Felt is one of the most affordable flat roof materials.
Strong multi layer protection
A typical felt roof uses an underlay and a mineral cap sheet for durability.
Easy to repair
Localised patches can be installed without replacing the full roof.
Good performance in cold weather
Modern torch on systems withstand frost and rain reliably.
Disadvantages
• Shorter lifespan compared to EPDM or GRP
• Vulnerable to UV degradation over time
• Requires torch equipment which demands skill and safety awareness
• Heavy compared to other materials
Best for:
• Garages
• Outbuildings
• Budget projects
• Areas with occasional foot traffic
Felt remains a widely used and reliable option especially for homeowners seeking an economical solution.
Liquid applied roofing systems
Liquid roofing products form a fully waterproof membrane once cured. They include acrylic, polyurethane, and PMMA based systems.
Key advantages
Seamless finish
Liquids create a single continuous waterproof layer with no seams.
Excellent adhesion
They bond well to many surfaces including old felt, concrete, timber, and metal.
Perfect for refurbishment
Liquid coatings are ideal when upgrading an existing roof without full replacement.
UV resistant and flexible
Most systems cope well with temperature changes and sunlight.
Disadvantages
• Must be applied in dry conditions
• Some systems require professional installers
• Cheaper products offer shorter lifespan
Best for:
• Refurbishing older roofs
• Complex roof shapes
• Commercial buildings
• Domestic roofs needing a high performance solution
Liquid systems offer excellent performance though the best results come from premium products installed professionally.
Single ply PVC and TPO membranes
Single ply membranes are commonly used on commercial buildings but increasingly appear in domestic settings.
Key advantages
Strong and lightweight
Single ply systems are lighter than felt or GRP making them ideal for large roofs.
Welded seams
Hot air welding creates very strong, watertight joints.
Good lifespan
A well installed membrane lasts 20 to 30 years.
Fire resistant
Many systems offer strong fire ratings.
Disadvantages
• Requires specialist installation
• Vulnerable to punctures
• Not ideal for heavy foot traffic
• Can be more expensive than felt
Best for:
• Large garages
• Commercial units
• Schools
• Extensions with large roof areas
Single ply membranes deliver high performance but usually require commercial level installation skills.
Comparing flat roof materials by category
To choose the best material for a flat roof in the UK you must compare based on lifespan, cost, durability, and suitability.
By lifespan
• EPDM: 20 to 30 years
• GRP: 20 to 30 years
• Single ply PVC or TPO: 20 to 30 years
• Liquid systems: 10 to 20 years depending on product
• Torch on felt: 10 to 20 years
By cost
From cheapest to most expensive:
- Torch on felt
- Liquid applied systems
- EPDM
- GRP
- Single ply membranes
By ease of installation
Easiest:
• EPDM
• Liquid systems
• Torch on felt (requires skill)
• GRP (weather dependent)
• Single ply membranes (specialist only)
By durability and strength
Strongest:
• GRP
• Single ply
• EPDM
• Torch on felt
• Liquid systems (depends on product)
Best flat roof material for a garage
Garages need a robust material that can withstand temperature changes, occasional access, and varied weather. The top choices include:
EPDM
Ideal because garages often have simple roof shapes allowing a single sheet installation.
Torch on felt
Cost effective and reliable for standard garage roofs.
GRP
Excellent for garages used as workshops or hobby rooms because of its strength.
Best material for a house extension flat roof
House extensions require a material that offers superior waterproofing and a neat appearance.
GRP
Often the best for small to medium extensions due to its clean finish and long lifespan.
EPDM
Great for extensions without complex detailing.
Single ply membranes
Ideal for larger extensions that need premium performance.
Best flat roof material for garden rooms and offices
Garden rooms often include insulation and heating which means the roof must offer good thermal stability.
GRP
Provides excellent structural stability and an attractive finish.
EPDM
A strong alternative budget wise.
Liquid systems
Useful for irregular shapes and modern designs.
Best flat roof material for commercial buildings
Commercial roofs often require fire resistant, large format, durable materials.
Single ply membranes
The preferred choice for large commercial spaces.
Liquid systems
Excellent for refurbishing older commercial roofs.
Torch on felt
Still widely used on small commercial units.
Real world UK examples
Example 1: Garage roof replacement in a suburban home
The homeowner wanted a durable, low maintenance solution with the shortest installation time. EPDM was chosen and installed in a single sheet. The roof is still performing well many years later.
Example 2: Rear extension in a 1930s semi
The extension roof was visible from bedroom windows. GRP was selected for its clean appearance and ability to mould neatly around the parapet wall.
Example 3: Commercial unit refurbishment
A leaking felt roof on a commercial building needed updating. A liquid applied system was chosen to avoid stripping the old roof and to minimise disruption.
Example 4: Shed roof in a rental property
A cost effective torch on felt system was installed because longevity and budget were the main considerations.
Mistakes homeowners make when choosing flat roof materials
Choosing based on cost alone
Cheaper felt may save money upfront but needs replacement sooner.
Using the wrong material for roof size
GRP works well on small roofs but can crack on very large areas due to thermal movement.
Not hiring qualified installers
Some materials such as single ply membranes require specialist skills.
Ignoring drainage
Even the best material fails if water pools on the roof.
Using poor quality trims or flashings
Edge detailing must be high quality to prevent leaks.
Maintenance requirements for each material
EPDM
Low maintenance. Keep free from debris.
GRP
Inspect topcoat occasionally for UV wear.
Felt
Check for cracks, lifting edges, and blistering.
Liquid systems
Inspect surface for wear in high traffic areas.
PVC or TPO membranes
Check welded seams periodically.
Conclusion: What is the best flat roof material in the UK
There is no single best material for every situation although some outperform others in specific scenarios.
Best overall for domestic roofs: EPDM or GRP
Both provide long lifespan, strong waterproofing, and good performance across different building types.
Best for garages and simple roofs: EPDM
Fast to install and durable.
Best for small extensions and visible roofs: GRP
Attractive finish and high durability.
Best for large commercial roofs: Single ply membranes
Lightweight and high performance.
Best budget option: Torch on felt
Affordable and reliable when installed correctly.
Best for refurbishment: Liquid applied systems
Ideal for overlaying existing roofs.
Choosing the best flat roof material depends on your building type, budget, and long term expectations. When installed correctly with proper detailing any of the major systems can deliver a waterproof, durable, and effective flat roof suited to the UK climate.