Sunbury-on-Thames at a glance
- Postcode districts
- TW16
- Population
- about 27,784 (GeoNames)
- Council area
- Spelthorne Borough Council
- Building approval
- Spelthorne Borough Council building control, or a registered building control approver
- Nearest main town
- Woking, about 8 miles
- Guide price region
- South East (+10% on West Midlands rates)
What makes a good extension roof in Sunbury-on-Thames?
Extension roofs in Sunbury-on-Thames are often replaced because the original was built cheaply: thin chipboard decks, little or no insulation and felt turned up the wall without a proper flashing. Twenty or thirty years on, those weaknesses show up as leaks at the back wall and a cold, damp ceiling.
Around Sunbury-on-Thames, flat roofs are common on newer estates where the first extension roofs are now being replaced and on terraced streets with flat-roofed rear kitchens and bathrooms. Much of the South East sits in the drier Thames catchment at roughly 730 mm of rain a year, so the usual failures are at joints, upstands and outlets rather than from sheer volume of rain.
How much does a new extension roof cost in Sunbury-on-Thames?
At South East guide rates, a 20 m² extension roof in EPDM with a new deck and insulation comes to £3,100–£5,350 including VAT. 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 | £3,100–£5,350 |
| Extension (20 m²), GRP, new deck + insulation | £3,300–£5,900 |
| Extension (20 m²), EPDM, insulation + 1 rooflight upstand | £3,300–£5,750 |
| Single garage (18 m²), EPDM rubber | £1,750–£3,100 |
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.
What's included?
- New abutment upstand and flashing, plus rebuilt rooflight kerbs
- Staged strip-out so the room stays weathertight
- Building control handled where needed, and a written workmanship guarantee
- Free survey of the roof, abutment and room below
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?
- West Molesey · 2 mi
- Ashford, Surrey · 3 mi
- Weybridge · 3 mi
- Esher · 3 mi
- Chertsey · 4 mi
- Staines-upon-Thames · 4 mi
Extension and kitchen roofs in Sunbury-on-Thames: questions
Do you cover Sunbury-on-Thames?
Yes. Sunbury-on-Thames is part of our Surrey coverage, including postcode districts TW16. 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 Sunbury-on-Thames?
Where the work needs approval it goes to Spelthorne Borough 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 Sunbury-on-Thames?
£3,100–£5,350 for a 20 m² extension roof in EPDM with a new deck and insulation, at South East guide rates including VAT. The fixed price comes after a free survey for new and replacement roofs.
Can you keep my existing roof lantern?
Often, if the lantern itself is sound. We lift it, rebuild the kerb, dress the new membrane up the upstand and refit the lantern.
Do I need my neighbour's permission to replace an extension roof?
Not for a like-for-like re-cover in most cases. The Party Wall Act in England and Wales can apply if the work raises or cuts into a shared wall, so we flag that at survey.