Flat roofs are typically used on structures for non-standard parts of the living areas.
Popular examples include extensions, garages and outbuildings in gardens. They have a pitch of around 10°.
This article will cover the sorts of costs you can expect to pay for a flat roof as well as other factors which may affect the price of flat roofs.
Cost per m²
The roof cost minus the finishings is roughly £99/m², as broken down below. To get the total flat roof cost, you’ll need to add the base cost (£99/m²) plus the type of finishing, which are given in the second table.
Base Costs
| Item | Labour Cost per m² | Material Cost per m² | Total Cost per m² |
|---|---|---|---|
| Ceiling Joists - 150mm x 75mm | £19 | £31 | £50 |
| Plywood - 18mm thick | £14 | £16 | £30 |
| Vapour Control Layer | £1 | £2 | £3 |
| Slab Insulation - 120mm thick Celotex | £7 | £22 | £2 |
| Total | £41 | £69 | £110 |
Total Costs Including Roof Finishing Layer
| Item | Cost per m² | Total Cost (Base + Roof Finishing) / m² |
|---|---|---|
| Fibreglass / GRP | £78 | £185 |
| PVC | £55 | £155 |
| Bitumen | £52 | £160 |
| EPDM Rubber | £65 | £170 |
| Roofing Felt | £30 | £130 |
| Zinc | £95 | £200 |
Additional Items
| Item | Cost |
|---|---|
| PVC Gutters | £20 / m |
| Aluminium Gutters | £36 / m |
| Flashings | £39 / m |
| Aluminium Downpipes | £46 / m |
| Flashings | £22 - £38 / m |
Factors That Affect Cost
Specification
Jobs can vary considerably. For example, there may be more additional items needed such as guttering and flashing. Other items that can vary the cost include multiple or complicated trims, ventilation and insulation.
Size
Larger roofs will cost less per m² than smaller ones. Generally over a 100m² would see a 5% reduction in cost.
Accessibility
Costs increase the higher the flat roof is, which is dependant on the storey it’s at. Flat roofs on a 3 storey building will be higher than one a few feet high for example. This is because scaffolding may be necessary at larger heights as well as less accessibility.
Tradesman’s Markup
Every business has different overheads and expensive, and businesses will factor these into their price different. Skilled tradesmen are more likely to be busy and can charge higher prices.
Although prices above give a good indication of what to pay, it’s not a good idea to always go for the cheapest. Standards can drop considerably if you go for the cheapest price.
Location
Areas in the south of England and London will be higher than in other parts of the country. The prices quoted in the table above apply for the South East or Outer London area. The adjustments below can be used to calculate costs in your area.
Region % Adjustment
South East (Southampton, Oxford, Kent, Outer London) 0
Inner London +4%
South West (Bristol, Exeter) -4%
West Midlands (Birmingham) -10%
East Midlands (Northampton, Nottingham, Leicester) -10%
East Anglia (Cambridge, Norwich, Ipswich) -5%
North West (Liverpool, Manchester) -12%
Yorkshire and Humberside (Leeds, Sheffield) -11%
North East (Newcastle, Sunderland) -10%
Scotland (Edinburgh, Glasgow) -6%
Wales (Cardiff, Swansea) -9%
Northern Ireland (Belfast) -12%
What to Look for in a Flat Roofing Contractor
It can be tempting to go with the lowest quote you receive when looking into quotes for repairing or replacing your flat roof. However, it pays to do additional research before signing off on a contractor.
Take time to ask each contractor the following questions to assure yourself that you will receive quality workmanship.
- How much experience do you have in replacing and repairing flat roofs?
- What’s the average cost of a flat roof repair or replacement in your experience?
- Will the old material be removed before the new layer?
- Are there any potential costs not included in the quote?
There are further steps you can take to ensure the quality of your tradesman. Find out what qualifications and accreditations they hold and ask for proof.
Certifications to look out for include:
- CSCS
- Bauder
- Constructionline
- NFRC
- CITB
- City & Guilds
- SMAS Worksafe Contractor
Don’t be afraid to ask if they have customer testimonials that they can share and, if possible, contact previous customers to verify the reviews. Finally, ask for photos or videos of previous jobs they’ve undertaken.
Reputable contractors will be more than happy to share all of these details with you; they want to win your business. If a contractor fails to provide adequate reassurance on any of these points, we suggest you look elsewhere.
While this may result in increased costs in the short term, it will provide you with long-term peace of mind and assurance that you will receive excellent customer service and quality workmanship.
Get Prices on Flat Roofing Near You
We’ve done our best to give you a good idea of what you can expect to pay for a flat roof.
However, our guides are not a substitute for a fixed written quote specifically for you.
We work with all the best roofers ready to price your job. Get free, no-obligation quotes in your local area and compare prices using the form below.
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About the Author
Alex Johnson is a qualified quantity surveyor and writer with a passion for conducting original research and uncovering the true cost of jobs. His cost data has been referenced by EDF Energy and the Scottish Government.