House extensions in Chalfont St Peter
From a small utility to a two-storey addition, we take on house extensions throughout Chalfont St Peter, starting with a free visit and a planning check.
- Postcode districtsSL9
- Price regionSouth East England (×1.12)
- Planning rulesEngland
- Site visitFree, no obligation
What works best for Chalfont St Peter houses?
Homes across the South East range from Victorian terraces in the older town centres to large detached houses on the edges, so the right extension type varies street by street.
Depending on the plot, wraparound extensions and double-storey extensions are often the strongest options, with orangery extensions worth considering where there is room.
Approvals for an extension in Chalfont St Peter
In England a single-storey rear extension can usually go up to 3 m beyond the original rear wall of a semi-detached or terraced house, or 4 m on a detached house, without a planning application, provided it is no more than 4 m high, keeps eaves to 3 m within 2 m of a boundary and, with other buildings, covers no more than half the land around the original house. The larger home extension prior approval scheme raises those depths to 6 m and 8 m, with neighbours notified and a 42-day decision.
In England a two-storey rear extension is permitted development only if it projects no more than 3 m from the original rear wall, sits at least 7 m from the rear boundary, matches the roof pitch and uses obscure, non-opening side windows upstairs. Most two-storey extensions therefore go through a householder planning application, which costs £548 from 1 April 2026 and normally takes about 8 weeks.
In a conservation area, national park, National Landscape, the Broads or a World Heritage Site the permitted development limits are tighter (no side or two-storey extensions without an application). Listed homes need listed building consent, and if permitted development rights have been removed, any extension needs an application.
Building regulations approval is separate from planning. In England you can use the council's building control team or a registered building control approver; a full plans application gets the drawings checked before work starts, and the inspector signs the work off with a completion certificate.
Applications are decided by the local planning authority (your district, borough or unitary council).
Guide prices for Chalfont St Peter
Prices on this page use our South East England factor of ×1.12, include VAT at 20% and cover the build; your written price follows a survey and agreed drawings.
| Extension type | Example size | Standard spec (inc VAT) |
|---|---|---|
| Extensions over a garage | 12 m² | £28,000 – £36,500 |
| Single-storey rear extensions | 20 m² | £45,500 – £58,500 |
| Kitchen extensions | 20 m² | £47,000 – £59,500 |
| Wraparound extensions | 25 m² | £64,000 – £81,500 |
| Orangery extensions | 16 m² | £50,000 – £63,000 |
| Side return extensions | 11 m² | £29,500 – £37,000 |
Areas we cover around Chalfont St Peter
Across SL9, we can visit, measure and advise. Neighbouring towns we cover include Gerrards Cross (2 miles), Amersham (5 miles), Chesham (7 miles), High Wycombe (8 miles), Marlow (10 miles). For homes towards Hertfordshire, Rickmansworth is around 4 miles away.
Extension types and starting prices
- Extensions over a garage · from £26,500
- Side extensions · from £24,500
- Single-storey rear extensions · from £23,500
- Kitchen extensions · from £30,000
- Bedroom extensions · from £29,000
- Porch extensions · from £4,450
- Annexe extensions · from £61,500
- Flat roof extensions · from £23,500
- Side return extensions · from £20,000
- Wraparound extensions · from £40,000
- Pitched roof extensions · from £24,500
- Home office extensions · from £17,500
- Orangery extensions · from £33,500
- Timber frame extensions · from £23,500
- Extension plans and drawings · from £1,300
- Bungalow extensions · from £29,000
- Planning permission for extensions · from £350
- Conservatory replacement extensions · from £22,000
- Building regulations for extensions · from £1,000
- Glass box extensions · from £33,500
- Double-storey extensions · from £42,500
- Utility and boot room extensions · from £15,500
Free site visit
It starts with a visit to your house to measure, check access and talk through ideas and budget.
Design and approvals
We produce the drawings and structural design, and manage the approvals so they are in place before work starts.
Fixed written price
We confirm the build price in writing, based on the approved drawings and the finishes you have chosen.
Build and sign-off
The build is managed from start to finish, inspected at each stage and signed off on completion.
Questions about extensions in Chalfont St Peter
How much does an extension cost in Chalfont St Peter?
Using our South East England factor (×1.12), a standard-spec single-storey extension of 20 m² is a guide £45,500 to £58,500 including VAT, and a 32 m² two-storey extension £64,500 to £84,500. Your written price follows the survey.
Who do I contract with?
Your contract is with S&K Property Investments and Improvement Ltd, which designs and manages the project and the build teams who carry it out.
Do you handle building regulations?
Yes. We prepare the drawings and calculations, submit them and book inspections, ending with a completion certificate.
How long does an extension take in Chalfont St Peter?
Usually 2 to 4 months of design and approvals, then 10 to 16 weeks on site for a single-storey extension or 16 to 24 weeks for two storeys.
Do I need planning permission for an extension in Chalfont St Peter?
Not always. It depends on the size, position and your property's history. Many single-storey rear extensions in England are permitted development or can use prior approval.
Book a free site visit in Chalfont St Peter
We will measure up, check the planning position and give you honest guide figures.
- Free, no-obligation site visit
- Planning route checked before you spend on drawings
- Written price once the design is agreed
- Building control sign-off at the end
Prefer to talk? Call 0800 088 6341 or .
Book a free site visit
Tell us a little about the project and we will arrange a time.