- Guide price
- £1,450–£2,750
- Survey
- Free for new and replacement roofs
- Quote
- Fixed, in writing
- Coverage
- England, Wales, Scotland, NI
Cornwall at a glance
How much does a new dormer roof cost in Cornwall?
Guide prices including VAT at South West rates. The fixed price comes after a free survey for new and replacement roofs.
| Job | Guide price inc VAT |
|---|---|
| Dormer (8 m²), GRP, scaffold | £1,450–£2,750 |
| Single garage (18 m²), EPDM rubber | £1,650–£2,900 |
| Extension (20 m²), GRP, new deck + insulation | £3,100–£5,550 |
Which flat roofs are common in Cornwall?
Flat roofs in Cornwall sit on lock-up garage blocks on estates, newer estates where the first extension roofs are now being replaced and terraced streets with flat-roofed rear kitchens and bathrooms. The South West averages roughly 1,260 mm of rain a year and many roofs face wind off the Atlantic, so we specify fixings and edge details for wind uplift as well as drainage. Approximate 1991–2020 regional averages based on Met Office data.
Building regulations in England
Replacing more than half of a roof over a heated room usually counts as renovating a thermal element, so it is insulated to current standards and notified to building control. Renovated roofs over heated rooms are insulated to around 0.16 W/m²K where that's feasible, and new extension roofs are built to 0.15 W/m²K. In Cornwall the application goes to Cornwall Council. More on the rules.
How long does a dormer roof replacement take?
The roofing itself typically takes one to three days, with scaffold going up before and coming down after. Allow a few extra days overall for the scaffold.
The room under the dormer stays usable, though it will be noisy during the strip-out, and dust can fall through gaps around the ceiling. Moving furniture away from the window helps. Scaffold usually needs space on the drive or garden, and sometimes a pavement licence. GRP has a strong smell while it cures, so keep the dormer windows shut on the day it is laid.
Do I need building regulations approval for a dormer roof?
Usually, yes, if you are replacing most of the roof. A dormer roof sits over a heated room, so it counts as a thermal element, and renovating more than half of it normally means upgrading the insulation where feasible.
In England the renovation target is 0.16 W/m²K for homes, approved through building control or a competent person scheme. Wales usually needs approval for most re-roofing work. Scotland works through the council's building standards and, where required, a building warrant. Northern Ireland asks you to contact district council building control before starting.
Insulating above the deck raises the roof slightly. On a dormer, that extra height has to fit under the main roof tiles at the back edge, so the build-up is planned at survey. Re-covering a dormer that looks the same afterwards does not usually need planning permission, but a listed building or conservation area may bring extra controls. More on our building regulations page.
Which towns in Cornwall do we cover?
Dormer roofs in Cornwall: questions
Which towns in Cornwall do you cover?
All of Cornwall. 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 dormer roof cost in Cornwall?
£1,450–£2,750 for an 8 m² GRP dormer roof including scaffold, at South West guide rates including VAT. The fixed price comes after a free survey for new and replacement roofs.
Which postcode areas do you cover in Cornwall?
All of Cornwall, including the PL, TR postcode areas. Send your full postcode and we'll confirm.
How long does a GRP dormer roof last?
As an indicative range, GRP lasts 20–40 years with good specification and maintenance.
Can a dormer roof be replaced without scaffold?
Rarely. A tower or full scaffold is usually needed to give a safe working platform and edge protection at that height.
Is a dormer roof cheaper than a garage roof?
Not by as much as the size suggests. Scaffold and the extra detailing at height mean a small dormer roof often costs about the same as a single garage roof.
Everything about dormer roofs → · All flat roofing in Cornwall →