A flat roof replacement strips the old covering from a low-pitched roof and lays a new waterproof system, usually EPDM rubber, GRP fibreglass or torch-on felt, over a sound deck with correct falls, upstands, trims and outlets so rainwater drains away.
Every house in Cardiff is a little different, so we never price a new flat roof from a brochure. We look at the structure, access and existing finishes first, then put in writing a fixed figure for the scope we settle on. As a rough steer, homeowners in Wales should budget £1,850–£4,100 including VAT, with work typically taking 1–3 days for most roofs.
- Guide price
- £1,850–£4,100 inc VAT
- Time on site
- 1–3 days for most roofs
- Postcodes
- CF10, CF11 and CF24
- Planning rules
- Wales
- Local area
- South Glamorgan
- Survey
- Free, with a written quote
How much does a new flat roof cost in Cardiff?
To help you plan, we show what a new flat roof typically costs in Cardiff instead of holding figures back for a sales call. The range is £1,850–£4,100 with VAT, using rates in Wales that are about 8% below the national guide. A free survey then fixes your actual price.
| Type of job | What it usually involves | Guide in Cardiff |
|---|---|---|
| Small roof (up to 8m²) | A dormer, bay, porch or small garage roof re-covered in EPDM or GRP. | £750–£1,850 |
| Extension or garage (15–25m²) | A typical extension or single garage roof stripped and re-covered. | £1,850–£4,100 |
| Large or new warm roof | Larger roofs, or roofs needing a new deck and insulation build-up. | £3,700–£8,300 |
The main things that change the figure:
- Roof area and access to the roof
- Covering system: EPDM, GRP or torch-on felt
- Condition of the deck and joists underneath
- Insulation upgrades and changes to roof height at edges
What does the job include in Cardiff?
- Survey of the covering, deck, falls, upstands and drainage
- Stripping and disposal of the old roof covering
- Insulation upgrade to a warm roof build-up where agreed
- New EPDM, GRP or torch-on felt membrane laid to falls
- Upstands, flashings and drip edges finished neatly
- New trims, outlets and gutter connections
Building in Cardiff
Cardiff has large areas of bay-fronted Victorian and Edwardian terraces in districts such as Roath, Canton and Cathays, plus interwar suburbs, post-war estates and modern flats around Cardiff Bay. Penarth has Victorian villas, Barry mixes terraces with newer estates, and Vale of Glamorgan villages are often built of local limestone.
Mild but wet, with coastal exposure along the Severn estuary and Bristol Channel affecting render, roofline and windows.
In Cardiff, as elsewhere in South Glamorgan, we take the building's age and construction into account before recommending anything, because both can change what is involved in a new flat roof.
Do you need permission in Cardiff?
For anyone in Cardiff, the relevant framework is Wales's. The summary below is general, so we always contact the council about your address before putting a price in writing.
Re-roofing with similar materials does not usually need planning permission in Wales, except on listed buildings or where a conservation area restricts materials.
Building Regulations in Wales apply to major re-roofing, including insulation upgrades. Bats are protected across the UK; if they roost under roof tiles, soffits or fascias, work stops and a licensed ecologist advises before it restarts.
Rules change and every property is different, so we check the planning history and constraints for your address before we quote.
What happens after you get in touch?
Survey and measure
We begin by looking at the job in person. During the free survey we discuss options, materials and budget for a new flat roof, and photograph or measure anything the quote needs to reflect.
Written quote
You get the price in writing, itemised so you can see where the money goes. As long as the specification stays the same, that is the price you pay for a new flat roof.
Dates and permissions
Next comes planning the work itself. We set a start date that suits you, line up the right trades, and make sure any approvals for a new flat roof are in place before the first day on site.
Build and hand over
The work is carried out to the agreed specification, with floors and furniture protected and the site kept tidy. At the end we clean up, walk through the finished job with you and hand over any certificates.
What you can expect from us
Flat roofs in Cardiff: questions
Is the price fixed?
Yes, for the specification we agree. Your written quote sets out exactly what is included at a fixed price. It only changes if you ask for something different, or if a problem the survey could not reasonably reveal later needs extra work. In either case we explain the change and confirm it in writing before going ahead.
Is a flat roof suitable for a roof terrace?
A flat roof can only be used as a terrace if it is designed for it, with joists strong enough for people and furniture, a hard-wearing surface, safe edge protection and correct drainage. Using a standard extension roof as a terrace can damage it and may need planning permission and building regulations approval. We can advise on what a conversion would involve.
Can you combine a new flat roof with other work?
Yes. Because we manage several trades under one contract, we can plan a new flat roof alongside other work on your Cardiff home, such as new windows with rendering, or a kitchen refit with an extension. Combining jobs can reduce repeat set-up such as scaffolding, skips and access, and every element is listed and priced in the same written quote.
How long does a flat roof last?
A well-installed EPDM or GRP flat roof can last 25 years or more, while torch-on felt systems typically last around 15–25 years, depending on quality and exposure. Lifespan depends on correct falls, good detailing at edges and upstands, and keeping outlets clear. Foot traffic, ponding and poor ventilation shorten it. Annual checks help catch small problems early.
Why does water sit on my flat roof?
Ponding water on a flat roof is usually caused by inadequate falls, sagging joists, a deck that has dipped or blocked outlets. Small puddles that dry within a day or two are not always a problem, but standing water speeds up wear and finds any weakness. A new roof can be laid on firring strips or tapered insulation to create proper falls. We check falls during the survey.
Near Cardiff
Homes across CF10, CF11 and CF24 in Cardiff are within our coverage, as are those in Penarth, Caerphilly and Barry. If you are just outside these areas, ask anyway, because we work right across the UK.