Cardiff at a glance
- Postcode districts
- CF3, CF5, CF10, CF11, CF14, CF15, CF23, CF24
- Population
- about 372,089 (GeoNames)
- Council area
- Cardiff Council
- Building approval
- Cardiff Council building control, or a registered building control approver
- Guide price region
- Wales (−8% on West Midlands rates)
When should a flat roof in Cardiff be replaced?
A mineral felt roof laid decades ago may still look intact from the ground in Cardiff, yet have lost its chippings, cracked at the laps and pulled away at the upstands. Those faults let water track under the covering, so by the time a ceiling stain appears, the deck has often been wet for some time.
In and around Cardiff, flat roofs are typically found on low-rise post-war blocks of flats, and on bungalows with flat-roofed side extensions and dormers. Wales averages roughly 1,460 mm of rain a year, among the wettest in Britain, so we design for steady run-off: proper falls, clear outlets and upstands well above the finished roof.
How much does a flat roof replacement cost in Cardiff?
Guide price in Cardiff: £2,600–£4,500 for a 20 m² extension roof in EPDM with a new deck and insulation, including VAT at Wales rates. The fixed price comes after a free survey for new and replacement roofs.
| Job | Guide price inc VAT |
|---|---|
| Extension (20 m²), EPDM, new deck + insulation | £2,600–£4,500 |
| Single garage (18 m²), torch-on felt | £1,400–£2,400 |
| Extension (20 m²), GRP, new deck + insulation | £2,750–£4,950 |
| Single garage (18 m²), EPDM rubber | £1,450–£2,600 |
Should I overlay my old flat roof or strip it fully?
Strip it fully if the deck is soft, the insulation is wet or the falls are wrong; an overlay only suits a dry, sound roof that already drains well. Covering a wet roof traps the moisture, and rot carries on out of sight.
An overlay also raises the roof level, eating into upstand height at walls and door thresholds, and every layer adds weight. In England, a covering that adds 15% or more to the roof's weight needs building control approval. Signs it is time to replace rather than repair:
- ponding that lingers long after rain
- blisters, cracking or crazing across wide areas
- bare bitumen where the mineral chippings have gone
- split laps and lifted upstands or flashings
- damp ceilings, or a deck that has gone soft
- leaks that return after each repair
A single defect on an otherwise dry roof can usually be put right with a repair. If you're unsure, a survey settles it, and our guides to overlay or strip and repair or replace go further.
What's included?
- Free survey of the deck, falls, edges and insulation
- New membrane, upstands, edge trims and outlets
- Building control handled where needed, plus a written workmanship guarantee
- New deck, firrings and warm-roof insulation where needed
Building regulations in Wales
The Welsh Approved Document L applies. Renovating more than half of a roof over a heated room means upgrading it to around 0.16 W/m²K where feasible, and new extension roofs are built to 0.13 W/m²K. Welsh Government guidance is that most re-roofing needs building control approval, so check whenever more than a quarter of a roof is replaced or repaired. We deal with the application as part of the job. More on the rules.
Which nearby areas do we also cover?
Flat roof replacement in Cardiff: questions
Do you cover Cardiff?
Yes. Cardiff is part of our Cardiff coverage, including postcode districts CF3, CF5, CF10, CF11, CF14, CF15 and 2 more. Surveys and roofs are carried out by vetted roofing teams working under S&K Property Investments and Improvement Ltd.
Who checks building regulations for a flat roof in Cardiff?
Where the work needs approval it goes to Cardiff Council building control, or a registered building control approver. We tell you at the survey whether your job needs it and deal with the paperwork as part of the quote.
How much does a flat roof replacement cost in Cardiff?
£2,600–£4,500 for a 20 m² extension roof in EPDM with a new deck and insulation, at Wales guide rates including VAT. The fixed price comes after a free survey for new and replacement roofs.
What time of year is best for a flat roof replacement?
Late spring to early autumn gives the most reliable dry spells, but a roof can be replaced in any season when the forecast allows. Adhesives and resins have minimum application temperatures, so winter work is planned around mild, dry days.
Can you replace just part of a flat roof?
Sometimes, if the rest is sound and dry. Renovating more than half of a roof over a heated room usually brings the whole roof under the insulation rules, so a full replacement can make more sense.