Chesham at a glance
- Postcode districts
- HP5
- Population
- about 20,649 (GeoNames)
- Council area
- Buckinghamshire Council
- Building approval
- Buckinghamshire Council building control, or a registered building control approver
- Nearest main town
- Hemel Hempstead, about 7 miles
- Guide price region
- South East (+10% on West Midlands rates)
What makes a good extension roof in Chesham?
Rooflights fitted after the roof was built are a frequent source of trouble in Chesham 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.
Chesham's flat roofs are mostly on 1930s semis with flat-roofed garages and kitchen extensions, with plenty on lock-up garage blocks on estates 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 Chesham?
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 |
Does an extension roof replacement need building regulations?
Usually, yes. An extension roof over a heated room is a thermal element, so replacing most of it typically brings insulation requirements and an approval route.
In England, renovating more than half of the roof means upgrading it towards 0.16 W/m²K where that is technically, functionally and economically feasible. The approval comes from building control or a competent person scheme. A brand-new extension roof is designed to 0.15. Wales usually requires approval for most re-roofing, with a renovation target of 0.16 and a new-extension target of 0.13. Scotland handles this through building standards and the warrant process, and Northern Ireland through district council building control.
Planning is not normally needed to re-cover an extension roof that looks broadly the same afterwards. Turning the roof into a terrace is another matter. We handle building control where the job needs it; see our building regulations page.
What's included?
- Building control handled where needed, and a written workmanship guarantee
- New abutment upstand and flashing, plus rebuilt rooflight kerbs
- Free survey of the roof, abutment and room below
- New deck, vapour control layer and warm-roof insulation
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?
- Amersham · 2 mi
- Berkhamsted · 4 mi
- Chalfont Saint Peter · 7 mi
- Rickmansworth · 7 mi
- Hemel Hempstead · 7 mi
- High Wycombe · 8 mi
Extension and kitchen roofs in Chesham: questions
Do you cover Chesham?
Yes. Chesham is part of our Buckinghamshire coverage, including postcode districts HP5. 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 Chesham?
Where the work needs approval it goes to Buckinghamshire 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 Chesham?
£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.
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.
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.