Cobham at a glance
- Postcode districts
- KT11
- Population
- about 16,724 (GeoNames)
- Council area
- Elmbridge Borough Council
- Building approval
- Elmbridge Borough Council building control, or a registered building control approver
- Nearest main town
- Woking, about 6 miles
- Guide price region
- South East (+10% on West Midlands rates)
What makes a good extension roof in Cobham?
Rooflights fitted after the roof was built are a frequent source of trouble in Cobham extensions. If the kerb was not formed properly or the membrane was simply sealed around the frame, leaks follow. Replacing the roof is the chance to rebuild every upstand to a proper standard.
Cobham's flat roofs are mostly on lock-up garage blocks on estates, with plenty on shops with flat-roofed rear stores below flats too. 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 Cobham?
For Cobham we use South East rates: £3,100–£5,350 is the guide for a 20 m² extension roof in EPDM with a new deck and insulation, VAT included. 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?
- Staged strip-out so the room stays weathertight
- New abutment upstand and flashing, plus rebuilt rooflight kerbs
- Falls set away from the house wall
- Building control handled where needed, and a written workmanship guarantee
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?
- Esher · 3 mi
- Weybridge · 4 mi
- Leatherhead · 4 mi
- West Molesey · 5 mi
- Sunbury-on-Thames · 5 mi
- Chertsey · 6 mi
Extension and kitchen roofs in Cobham: questions
Do you cover Cobham?
Yes. Cobham is part of our Surrey coverage, including postcode districts KT11. 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 Cobham?
Where the work needs approval it goes to Elmbridge 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 Cobham?
£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 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.
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.