- Guide price
- £2,600–£4,500
- Survey
- Free for new and replacement roofs
- Quote
- Fixed, in writing
- Coverage
- England, Wales, Scotland, NI
Caerphilly at a glance
- Largest towns
- Caerphilly, Risca, Gelligaer, Blackwood
- Postcode areas
- CF, NP
- Building control
- Caerphilly County Borough Council
- Neighbouring areas
- Torfaen · Merthyr Tydfil · Blaenau Gwent · Newport
- Guide price region
- Wales (−8% on West Midlands rates)
How much does a new extension roof cost in Caerphilly?
Guide prices 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 |
| Extension (20 m²), GRP, new deck + insulation | £2,750–£4,950 |
| Extension (20 m²), EPDM, insulation + 1 rooflight upstand | £2,750–£4,800 |
| Single garage (18 m²), EPDM rubber | £1,450–£2,600 |
Which flat roofs are common in Caerphilly?
Flat roofs in Caerphilly sit on 1960s and 1970s link-detached houses with flat-roofed garages and porches, bungalows with flat-roofed side extensions and dormers and low-rise post-war blocks of flats. 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. Approximate 1991–2020 regional averages based on Met Office data.
Building regulations in Wales
Welsh guidance is that most re-roofing needs building control approval, so it's worth checking whenever more than a quarter of a roof is replaced or repaired. Renovated roofs are upgraded to around 0.16 W/m²K where feasible, and new extension roofs are built to 0.13 W/m²K under the Welsh Approved Document L. In Caerphilly the application goes to Caerphilly County Borough Council. More on the rules.
Does an extension roof replacement need building regulations?
Usually, yes. An extension roof over a heated room is a thermal element, so replacing most of it typically brings insulation requirements and an approval route.
In England, renovating more than half of the roof means upgrading it towards 0.16 W/m²K where that is technically, functionally and economically feasible. The approval comes from building control or a competent person scheme. A brand-new extension roof is designed to 0.15. Wales usually requires approval for most re-roofing, with a renovation target of 0.16 and a new-extension target of 0.13. Scotland handles this through building standards and the warrant process, and Northern Ireland through district council building control.
Planning is not normally needed to re-cover an extension roof that looks broadly the same afterwards. Turning the roof into a terrace is another matter. We handle building control where the job needs it; see our building regulations page.
How long will my kitchen be disrupted by a new roof?
Most single-storey extension roofs are replaced in two to four working days, depending on size, rooflights and weather. The kitchen usually stays in use throughout.
Expect noise during the strip-out, and occasional dust through gaps around old rooflights, so it helps to cover worktops and move anything fragile off high shelves. We strip only what we can make weathertight by the end of each day. If a rooflight or lantern is being lifted and refitted, there may be a temporary cover over the opening for a short time. Resin systems smell while they cure, so keep the windows below the roof closed on that day.
Which towns in Caerphilly do we cover?
Extension and kitchen roofs in Caerphilly: questions
Which towns in Caerphilly do you cover?
All of Caerphilly. The main towns have their own pages below, and if yours isn't listed we still cover it: send your postcode and we'll confirm.
How much does a new extension roof cost in Caerphilly?
£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.
Which council handles building control for a flat roof in Caerphilly?
It depends on where the roof is: in Caerphilly that's Caerphilly County Borough Council. Welsh guidance is that most re-roofing needs building control approval, so it's worth checking whenever more than a quarter of a roof is replaced or repaired. We confirm which applies at the survey.
How do I know my extension roof needs replacing rather than repairing?
Repeated leaks, a soft deck, wet insulation or widespread cracking point to replacement. A single defect on a dry, sound roof can usually be repaired.
Can a sedum roof go on my extension?
Possibly, if the structure can carry the extra weight and the roof has suitable falls and drainage. We check the joists at survey before recommending it.
Why does my extension ceiling get damp in winter if the roof isn't leaking?
That is often condensation in a cold roof, where warm, moist air reaches the cold underside of the deck. A warm-roof replacement with a vapour control layer usually solves it.
Everything about extension and kitchen roofs → · All flat roofing in Caerphilly →