Westminster at a glance
- Postcode districts
- W1K, W1C, W1H, W1U, W1M, W1G, W1, W1J and 20 more
- Council area
- City of Westminster
- Building approval
- City of Westminster building control, or a registered building control approver
- Guide price region
- London (+20% on West Midlands rates)
When should a flat roof in Westminster be replaced?
A mineral felt roof laid decades ago may still look intact from the ground in Westminster, yet have lost its chippings, cracked at the laps and pulled away at the upstands. Those faults let water track under the covering, so by the time a ceiling stain appears, the deck has often been wet for some time.
In a town like Westminster, flat roofs are commonly found on mansard and dormer loft conversions or kitchen extensions and roof terraces behind period houses. 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 Westminster?
For Westminster 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 |
| 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 |
Do I need building regulations approval to replace a flat roof?
Often, yes. Replacing the covering of a flat roof over a heated room is usually treated as renovating a thermal element, which brings insulation requirements and, in most cases, approval.
In England, if more than half of that roof is renovated, the whole roof should be upgraded towards a U-value of 0.16 W/m²K for homes (0.18 for non-domestic buildings) where that is technically, functionally and economically feasible, judged against a simple payback of 15 years. Approval comes from building control or self-certification through a registered competent person scheme. Structural changes, or a covering that adds 15% or more to the roof's weight, also need approval.
The other nations differ: most re-roofing in Wales needs approval, Scotland works through building standards and the building warrant, and in Northern Ireland you contact the district council's building control first. An unheated detached garage is not normally a thermal element. Planning permission is not usually needed if the roof looks much the same afterwards, though listed buildings and conservation areas are different. We handle approvals where needed; see building regulations.
What's included?
- New deck, firrings and warm-roof insulation where needed
- Building control handled where needed, plus a written workmanship guarantee
- New membrane, upstands, edge trims and outlets
- Fixed written quote listing the full build-up
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?
- Camden · 1 mi
- Kensington and Chelsea · 2 mi
- Islington · 3 mi
- Hammersmith and Fulham · 3 mi
- Lambeth · 4 mi
- Southwark · 4 mi
Flat roof replacement in Westminster: questions
Do you cover Westminster?
Yes. Westminster is part of our London coverage, including postcode districts W1K, W1C, W1H, W1U, W1M, W1G and 22 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 Westminster?
Where the work needs approval it goes to City of Westminster 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 Westminster?
£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.
Do I need to be at home while the roof is replaced?
Not for most of the job, as long as the team can reach the roof and there is room for a skip. We ask you to be there at the start to agree the plan and at the end to look over the finished roof.
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.