TL;DR
- Garage flat roofing: £750–£2,200 (single to double garage, EPDM)
- Extension flat roofing: £800–£3,500+ depending on size
- Porch flat roofing: £350–£850
- Per square metre: £45–£80 for quality EPDM including installation
- Felt roofing costs 30–40% less initially but needs replacing 2–3 times sooner
- Factors affecting cost: size, complexity, deck condition, access, and insulation requirements
- South Wales pricing is typically 10–15% below London rates
- Always compare total cost of ownership, not just upfront price
“How much will my flat roof cost?” is the first question most homeowners ask—and rightly so. You need realistic figures to budget properly, evaluate quotes, and avoid surprises.
This guide provides current 2026 flat roofing prices across the UK, with specific guidance for South Wales. We cover every common application, explain what affects pricing, and help you understand what represents fair value.
Flat Roofing Costs at a Glance
Quick reference prices for the most common projects:
| Project Type | Size Range | 2026 Cost Range (EPDM) |
|---|---|---|
| Bay window roof | 2–4m² | £300–£600 |
| Small porch | 2–5m² | £350–£600 |
| Large porch | 5–10m² | £500–£950 |
| Single garage | 15–20m² | £750–£1,400 |
| Double garage | 30–40m² | £1,200–£2,200 |
| Small extension | 10–20m² | £800–£1,600 |
| Medium extension | 20–35m² | £1,400–£2,800 |
| Large extension | 35–50m² | £2,200–£3,800 |
| Garden room | 15–25m² | £1,000–£2,000 |
These prices include quality EPDM membrane, standard insulation, edge details, and professional installation.
Cost Per Square Metre
Understanding per-metre rates helps evaluate quotes for any roof size.
EPDM Rubber Roofing
| Roof Size | Cost Per m² (Installed) |
|---|---|
| Under 10m² | £65–£85 |
| 10–20m² | £55–£75 |
| 20–40m² | £50–£65 |
| 40–60m² | £45–£60 |
| Over 60m² | £40–£55 |
Smaller roofs cost more per square metre because fixed costs (travel, setup, minimum charges) spread across less area.
Felt Roofing
| Roof Size | Cost Per m² (Installed) |
|---|---|
| Under 10m² | £45–£60 |
| 10–20m² | £40–£55 |
| 20–40m² | £35–£50 |
| Over 40m² | £30–£45 |
Felt costs less per metre but lasts only 10–15 years versus 30–50 for EPDM.
Fibreglass (GRP)
| Roof Size | Cost Per m² (Installed) |
|---|---|
| Under 10m² | £70–£90 |
| 10–20m² | £60–£80 |
| 20–40m² | £55–£70 |
| Over 40m² | £50–£65 |
GRP typically costs similar to or slightly more than EPDM with shorter lifespan.
Garage Flat Roofing Costs
Garages are the most common flat roofing project.
Single Garage
Typical dimensions: 3m × 5m to 3m × 6m (15–18m²)
| Component | Cost Range |
|---|---|
| EPDM membrane | £250–£350 |
| Insulation | £150–£250 |
| Edge trims and details | £100–£150 |
| Labour | £350–£550 |
| Total | £750–£1,400 |
What affects single garage pricing:
- Deck condition (replacement adds £250–£450)
- Penetrations (vents, pipes add £50–£100 each)
- Access difficulties (restricted access adds 10–20%)
Double Garage
Typical dimensions: 6m × 5m to 6m × 7m (30–42m²)
| Component | Cost Range |
|---|---|
| EPDM membrane | £450–£650 |
| Insulation | £300–£450 |
| Edge trims and details | £150–£250 |
| Labour | £450–£750 |
| Total | £1,200–£2,200 |
Triple/Large Garage
Typical dimensions: 9m × 6m+ (54m²+)
Cost range: £1,800–£3,200
Larger garages benefit from better per-metre rates as fixed costs spread further.
Garage Flat Roofing: Felt vs EPDM Cost Comparison
| Material | Initial Cost | Expected Lifespan | 30-Year Cost |
|---|---|---|---|
| Felt | £500–£900 | 10–15 years | £1,500–£2,700 |
| EPDM | £750–£1,400 | 30–50 years | £750–£1,400 |
Despite higher initial cost, EPDM costs less over time.
Extension Flat Roofing Costs
Extensions vary widely in size and complexity.
Small Extensions (10–20m²)
Typical projects: Single-room additions, utility rooms, small kitchen extensions.
| Component | Cost Range |
|---|---|
| EPDM membrane | £200–£400 |
| Insulation (building regs compliant) | £200–£350 |
| Edge details and upstands | £150–£250 |
| Labour | £350–£600 |
| Total | £800–£1,600 |
Medium Extensions (20–35m²)
Typical projects: Kitchen-diners, larger single-storey additions.
| Component | Cost Range |
|---|---|
| EPDM membrane | £350–£600 |
| Insulation | £350–£550 |
| Edge details and upstands | £200–£350 |
| Labour | £500–£850 |
| Total | £1,400–£2,800 |
Large Extensions (35–50m²)
Typical projects: Substantial rear extensions, wraparound extensions.
| Component | Cost Range |
|---|---|
| EPDM membrane | £550–£850 |
| Insulation | £500–£750 |
| Edge details and upstands | £300–£450 |
| Labour | £700–£1,100 |
| Total | £2,200–£3,800 |
Extension Pricing Factors
Skylights: Add £75–£200 per skylight for proper sealing.
Roof lanterns: Integration adds £150–£400 depending on size.
Complex shapes: L-shaped or multi-section roofs cost 15–25% more than simple rectangles.
Building regulations compliance: Standard for extensions; insulation costs reflect current requirements.
Porch Flat Roofing Costs
Porches are smaller but still require proper attention.
Small Porch (2–5m²)
Cost range: £350–£600
Small porches have higher per-metre costs due to minimum charges, but total cost remains modest.
Medium Porch (5–8m²)
Cost range: £500–£750
Large Porch (8–12m²)
Cost range: £650–£950
Porch Pricing Notes
- Front porches may be more visible, affecting finish requirements
- Integration with house door and walls needs careful detailing
- Small area means labour is proportionally higher than materials
Dormer Flat Roofing Costs
Dormers require access consideration as well as roofing.
Standard Dormer (5–8m²)
| Component | Cost Range |
|---|---|
| EPDM membrane and insulation | £350–£550 |
| Edge and integration details | £150–£250 |
| Labour | £200–£350 |
| Roofing total | £600–£1,000 |
Access Costs
| Access Method | Additional Cost |
|---|---|
| Roof ladder (simple access) | £0–£100 |
| Scaffold tower | £150–£300 |
| Full scaffolding | £400–£700 |
Note: If scaffolding is already in place for loft conversion, dormer roofing access cost may be absorbed into main project.
Multiple Dormers
Second and subsequent dormers typically cost 10–20% less per unit due to setup efficiency.
Other Flat Roofing Costs
Bay Window Roofs
Size: Typically 2–4m²
Cost range: £300–£600
Bay window roofs often have complex shapes requiring careful detailing. Poor access can increase costs.
Conservatory Roof Conversions
Converting glazed conservatory roof to solid, insulated flat roof:
| Conservatory Size | Conversion Cost |
|---|---|
| Small (8m²) | £1,800–£3,000 |
| Medium (12m²) | £2,800–£4,500 |
| Large (20m²) | £4,500–£7,000 |
Includes structural assessment, new roof build-up, insulation, membrane, and internal ceiling.
Garden Rooms and Outbuildings
| Building Size | Flat Roofing Cost |
|---|---|
| Small shed (6m²) | £400–£650 |
| Medium outbuilding (12m²) | £650–£1,100 |
| Garden room (20m²) | £1,100–£1,800 |
| Large garden building (30m²) | £1,500–£2,500 |
Commercial Flat Roofing
Commercial projects achieve better per-metre rates:
| Roof Size | Cost Per m² |
|---|---|
| 100–200m² | £50–£70 |
| 200–500m² | £45–£60 |
| 500–1,000m² | £40–£55 |
| Over 1,000m² | £35–£50 |
What’s Included in Flat Roofing Prices
Understanding what quotes should include helps comparison.
Standard Inclusions
Materials:
- EPDM membrane (or specified alternative)
- Insulation boards (to building regulations where applicable)
- Adhesives and primers
- Edge trims and drip details
- Upstand termination materials
- Sealants
Labour:
- Removal of existing covering (replacement projects)
- Deck inspection
- Installation of all materials
- Edge detail execution
- Penetration sealing
- Clean-up and waste removal
Documentation:
- Warranty information
- Specification details
Common Exclusions
Often quoted separately:
- Scaffolding or access equipment
- Deck repair or replacement
- Building regulations fees
- Skip hire (large projects)
- Additional insulation above standard
Always confirm what’s included and excluded when comparing quotes.
Factors Affecting Flat Roofing Costs
Understanding cost factors helps explain quote variations.
Roof Size
Impact: Major
Larger roofs cost more in total but less per square metre. Fixed costs (travel, setup, minimum trades) spread across greater area.
Roof Complexity
Impact: Moderate to Major
| Complexity Factor | Cost Impact |
|---|---|
| Simple rectangle | Baseline |
| L-shape | +10–15% |
| Multiple sections | +15–25% |
| Many penetrations | +£50–150 each |
| Unusual shapes | +20–40% |
Deck Condition
Impact: Variable
| Deck Condition | Additional Cost |
|---|---|
| Sound (no work needed) | £0 |
| Minor repairs | £100–£300 |
| Partial replacement | £300–£600 |
| Full replacement | £500–£1,200+ |
Deck condition is often unknown until existing covering is removed.
Access
Impact: Low to Moderate
| Access Situation | Cost Impact |
|---|---|
| Ground level, clear access | Baseline |
| Restricted vehicle access | +5–10% |
| Material handling through house | +10–15% |
| Scaffolding required | +£300–£700 |
| Difficult roof access | +10–20% |
Insulation Requirements
Impact: Moderate
| Insulation Level | Cost Per m² |
|---|---|
| No insulation (not over heated space) | Baseline |
| Standard building regs (100mm PIR) | +£15–£20 |
| Enhanced (150mm PIR) | +£22–£28 |
| High performance (200mm+) | +£30–£40 |
Location
Impact: Low to Moderate
| Region | vs UK Average |
|---|---|
| London and South East | +15–25% |
| South Wales | -5–15% |
| Midlands | Baseline |
| Northern England | -5–10% |
| Scotland | Variable |
South Wales typically offers competitive pricing compared to national averages.
Timing
Impact: Low
| Timing Factor | Cost Impact |
|---|---|
| Standard scheduling | Baseline |
| Urgent/emergency | +20–50% |
| Flexible timing | Potential discount |
| Winter installation | Usually no difference |
Regional Pricing: South Wales
Flat roofing costs in South Wales are generally competitive.
South Wales vs National Average
Most South Wales flat roofing projects cost 5–15% below London and South East prices. This reflects:
- Lower operating costs
- Competitive local market
- Strong installer availability
Local Pricing Examples
For a typical single garage flat roof in South Wales:
| Area | Typical Cost Range |
|---|---|
| Cardiff | £850–£1,300 |
| Swansea | £800–£1,250 |
| Newport | £800–£1,200 |
| Merthyr Tydfil | £750–£1,200 |
| Aberdare | £750–£1,150 |
| Valleys generally | £700–£1,150 |
Valley areas often benefit from slightly lower rates than larger urban centres.
Flat Roof Repair Costs
Not every situation needs full replacement.
Common Repair Costs
| Repair Type | Cost Range |
|---|---|
| Patch repair (single puncture) | £75–£175 |
| Edge re-sealing | £100–£300 |
| Penetration seal repair | £80–£200 |
| Blister repair | £75–£175 |
| Multiple patch repairs | £200–£450 |
| Drainage improvement | £150–£500 |
When Repair vs Replacement
Repair if:
- Damage is localised
- Roof is under 15 years old (EPDM) or 8 years (felt)
- Rest of roof is sound
- Repair cost is under 40% of replacement
Replace if:
- Problems are widespread
- Roof approaching end of life
- Repairs keep recurring
- Repair cost approaches replacement cost
Getting Good Value
How to ensure fair pricing and quality outcomes.
Getting Quotes
Best practice:
- Obtain at least three quotes
- Ensure quotes cover same scope
- Ask about material specifications
- Confirm what’s included/excluded
- Check warranty offerings
- Verify insurance and credentials
Quote Comparison Checklist
| Element | Quote 1 | Quote 2 | Quote 3 |
|---|---|---|---|
| Total price | |||
| Material specified | |||
| Insulation included | |||
| Deck inspection | |||
| Edge details | |||
| Warranty (material) | |||
| Warranty (workmanship) | |||
| Access included | |||
| Waste removal |
Red Flags in Quotes
Be cautious of:
- Significantly below-market prices
- Vague specifications (“flat roof covering”)
- No mention of insulation
- Very short warranties
- Pressure for immediate decision
- Cash-only requests
- No written documentation
Value vs Price
Remember: The cheapest quote may not offer best value.
| Factor | Cheap Quote | Quality Quote |
|---|---|---|
| Material | Basic felt | Quality EPDM |
| Lifespan | 10–12 years | 35–45 years |
| Upfront cost | £600 | £1,100 |
| 35-year cost | £1,800+ | £1,100 |
Payment and Warranties
Understanding payment terms and warranty protection.
Typical Payment Terms
Standard approach:
- Deposit: 10–25% on acceptance
- Balance: On completion
Be cautious of:
- Large upfront deposits (over 30%)
- Full payment before completion
- No written receipt or invoice
Warranty Expectations
| Warranty Type | Typical Duration |
|---|---|
| EPDM material warranty | 20–25 years |
| Workmanship guarantee | 10–20 years |
| Felt material warranty | 10–15 years |
| Insurance-backed guarantee | Optional, adds cost |
Documentation: Ensure you receive warranty certificates and keep them safely.
Frequently Asked Questions
Why do quotes vary so much?
Quote variation typically reflects:
- Different material specifications
- Different scope (what’s included)
- Different quality expectations
- Regional pricing differences
- Installer experience and overheads
Comparing like-for-like reduces apparent variation.
Should I choose the cheapest quote?
Not automatically. Consider:
- What materials are specified?
- What’s the expected lifespan?
- What warranties are offered?
- Is the installer experienced?
Quality installation at fair price delivers better value than cheap work that fails.
Can I supply my own materials?
Possible but usually not advisable:
- You lose material warranty typically
- Responsibility for material quality shifts to you
- Savings are often minimal
- Installer may not guarantee work on materials they didn’t supply
Is flat roofing more expensive than pitched?
Generally no—flat roofing typically costs 20–40% less than pitched alternatives for the same coverage area due to simpler structure and fewer materials.
How do I budget for flat roofing?
Approach:
- Identify your project type
- Estimate roof size (length × width)
- Use price tables for range
- Add 10–15% contingency
- Consider access costs if applicable
Summary: 2026 UK Flat Roofing Prices
Current flat roofing prices reflect stable material costs and strong installer availability. Quality EPDM installation remains the best value choice for most applications.
Key 2026 pricing points:
- Single garage: £750–£1,400
- Double garage: £1,200–£2,200
- Small extension: £800–£1,600
- Medium extension: £1,400–£2,800
- Per square metre: £45–£80 (size dependent)
Value priorities:
- EPDM costs more initially but less over time
- Quality installation ensures full material lifespan
- Proper specification (insulation, details) prevents future problems
- Comprehensive warranties protect your investment
Get Your Flat Roofing Quote
At M&J Roofing, we provide clear, detailed quotations for flat roofing across South Wales. Our prices include quality EPDM materials, proper insulation, professional installation, and comprehensive warranties.
Contact us for a no-obligation quote. We’ll assess your specific requirements, explain your options, and provide transparent pricing you can rely on.
