Kensington and Chelsea at a glance
- Postcode districts
- W8, SW5, SW7, W11, SW10, SW3, W10
- Council area
- Royal Borough of Kensington and Chelsea
- Building approval
- Royal Borough of Kensington and Chelsea building control, or a registered building control approver
- Guide price region
- London (+20% on West Midlands rates)
What makes a good extension roof in Kensington and Chelsea?
Ponding against the house wall is a common reason for replacing an extension roof in Kensington and Chelsea. When the deck dips near the wall or the fall runs the wrong way, water sits against the abutment and eventually gets in. A new roof with corrected falls moves the water to the gutter.
Kensington and Chelsea's flat roofs are mostly on Victorian and Edwardian terraces with flat-roofed back additions, with plenty on kitchen extensions and roof terraces behind period houses too. The Thames basin is one of the drier parts of Britain at roughly 730 mm of rain a year, but summer heat is the bigger test here: dark membranes on south-facing roofs swing a long way in temperature.
How much does a new extension roof cost in Kensington and Chelsea?
For Kensington and Chelsea we use London rates: £3,350–£5,850 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 | £3,350–£5,850 |
| Extension (20 m²), GRP, new deck + insulation | £3,600–£6,450 |
| Extension (20 m²), EPDM, insulation + 1 rooflight upstand | £3,600–£6,300 |
| Single garage (18 m²), EPDM rubber | £1,900–£3,350 |
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
- Falls set away from the house wall
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?
- Hammersmith and Fulham · 1 mi
- Westminster · 2 mi
- Camden · 3 mi
- Wandsworth · 3 mi
- Lambeth · 4 mi
- Islington · 5 mi
Extension and kitchen roofs in Kensington and Chelsea: questions
Do you cover Kensington and Chelsea?
Yes. Kensington and Chelsea is part of our London coverage, including postcode districts W8, SW5, SW7, W11, SW10, SW3 and 1 more. 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 Kensington and Chelsea?
Where the work needs approval it goes to Royal Borough of Kensington and Chelsea 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 Kensington and Chelsea?
£3,350–£5,850 for a 20 m² extension roof in EPDM with a new deck and insulation, at London 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.
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.