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)
When should a flat roof in Kensington and Chelsea be replaced?
A sensible moment to replace a flat roof in Kensington and Chelsea is when other work is planned on the house, such as a kitchen refit below, new windows or a loft conversion. Doing the roof first protects the new work, and it is the natural time to upgrade insulation to the level the regulations expect for a renovated roof.
Kensington and Chelsea's flat roofs are mostly on Victorian and Edwardian terraces with flat-roofed back additions, with plenty on mansard and dormer loft conversions 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 flat roof replacement cost in Kensington and Chelsea?
At London guide rates, a 20 m² extension roof in EPDM with a new deck and insulation comes to £3,350–£5,850 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 | £3,350–£5,850 |
| Single garage (18 m²), torch-on felt | £1,800–£3,150 |
| Extension (20 m²), GRP, new deck + insulation | £3,600–£6,450 |
| Single garage (18 m²), EPDM rubber | £1,900–£3,350 |
Should I overlay my old flat roof or strip it fully?
Strip it fully if the deck is soft, the insulation is wet or the falls are wrong; an overlay only suits a dry, sound roof that already drains well. Covering a wet roof traps the moisture, and rot carries on out of sight.
An overlay also raises the roof level, eating into upstand height at walls and door thresholds, and every layer adds weight. In England, a covering that adds 15% or more to the roof's weight needs building control approval. Signs it is time to replace rather than repair:
- ponding that lingers long after rain
- blisters, cracking or crazing across wide areas
- bare bitumen where the mineral chippings have gone
- split laps and lifted upstands or flashings
- damp ceilings, or a deck that has gone soft
- leaks that return after each repair
A single defect on an otherwise dry roof can usually be put right with a repair. If you're unsure, a survey settles it, and our guides to overlay or strip and repair or replace go further.
What's included?
- Free survey of the deck, falls, edges and insulation
- New deck, firrings and warm-roof insulation where needed
- Strip-out of the old covering, with waste and skip
- New membrane, upstands, edge trims and outlets
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
Flat roof replacement 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 flat roof replacement 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.
What guarantees come with a replacement roof?
Every re-roof comes with a written workmanship guarantee, with the length set out in your quote. Manufacturer material guarantees are available on many systems and we register them for you where the system allows; ask about insurance-backed options too.
Will a replacement make my roof higher?
Usually a little, if insulation is added above the deck. We check door thresholds, window sills, upstands and wall flashings at survey so the new level works.