Trowbridge at a glance
- Postcode districts
- BA14
- Population
- about 40,952 (GeoNames)
- Council area
- Wiltshire Council
- Building approval
- Wiltshire Council building control, or a registered building control approver
- Nearest main town
- Bath, about 8 miles
- Guide price region
- South West (+3% on West Midlands rates)
What makes a good extension roof in Trowbridge?
If you're fitting a new kitchen under an extension in Trowbridge, that's a good time to replace the roof. It makes sense to rebuild the roof before fitting new units, ceilings and lighting below, and the insulation upgrade makes the room more comfortable all year.
In a town like Trowbridge, flat roofs are commonly found on shops with flat-roofed rear stores below flats or bungalows with flat-roofed side extensions and dormers. 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.
How much does a new extension roof cost in Trowbridge?
Guide price in Trowbridge: £2,900–£5,050 for a 20 m² extension roof in EPDM with a new deck and insulation, including VAT at South West 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 | £2,900–£5,050 |
| Extension (20 m²), GRP, new deck + insulation | £3,100–£5,550 |
| Extension (20 m²), EPDM, insulation + 1 rooflight upstand | £3,100–£5,400 |
| Single garage (18 m²), EPDM rubber | £1,650–£2,900 |
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.
What's included?
- Free survey of the roof, abutment and room below
- Staged strip-out so the room stays weathertight
- New abutment upstand and flashing, plus rebuilt rooflight kerbs
- New deck, vapour control layer and warm-roof insulation
Building regulations in England
Replacing more than half of a flat roof over a heated room usually counts as renovating a thermal element, so the roof is insulated to around 0.16 W/m²K where that's technically and economically feasible, and the work is notified to building control: the council or a registered building control approver, unless a registered competent person self-certifies it. A roof on a new extension is built to 0.15 W/m²K. Patch repairs, and most unheated detached garages, don't trigger the upgrade. Structural changes, or a new covering that adds 15% or more to the roof's weight, also need approval. More on the rules.
Which nearby areas do we also cover?
Extension and kitchen roofs in Trowbridge: questions
Do you cover Trowbridge?
Yes. Trowbridge is part of our Wiltshire coverage, including postcode districts BA14. 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 Trowbridge?
Where the work needs approval it goes to Wiltshire 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 new extension roof cost in Trowbridge?
£2,900–£5,050 for a 20 m² extension roof in EPDM with a new deck and insulation, at South West guide rates including VAT. The fixed price comes after a free survey for new and replacement roofs.
Is EPDM or GRP better for a kitchen extension?
Neither is better in every case. EPDM suits simple rectangular roofs with few details, while GRP is often chosen where there are rooflights, corners or occasional foot traffic.
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.