Bletchley house extensions
Planning an extension in Bletchley? Compare extension types, see guide prices adjusted for Bletchley and book a free site visit.
- Postcode districtsMK1, MK2, MK3, MK4, MK6, MK17
- Price regionSouth East England (×1.12)
- Planning rulesEngland
- Site visitFree, no obligation
Where we work near Bletchley
Our survey diary covers Bletchley, including MK1, MK2, MK3, MK4, MK6, MK17. We also work in nearby Milton Keynes (3 miles), Aylesbury (13 miles), Chesham (21 miles), Amersham (23 miles), High Wycombe (25 miles). Leighton Buzzard, in Bedfordshire, is roughly 6 miles from Bletchley and also on our list.
What works best for Bletchley houses?
The South East has a broad mix of 1930s semis, post-war estates, newer developments and period cottages, and many houses have enough garden for a generous rear extension.
Start by comparing orangery extensions, single-storey rear extensions and wraparound extensions: between them they cover most of the layouts we see requested for houses like these.
Guide prices for Bletchley
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) |
|---|---|---|
| Double-storey extensions | 32 m² | £64,500 – £84,500 |
| Conservatory replacement extensions | 14 m² | £33,500 – £43,500 |
| Kitchen extensions | 20 m² | £47,000 – £59,500 |
| Extensions over a garage | 12 m² | £28,000 – £36,500 |
| Single-storey rear extensions | 20 m² | £45,500 – £58,500 |
Do extensions in Bletchley need planning permission?
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).
Extension types and starting prices
- Annexe extensions · from £61,500
- Conservatory replacement extensions · from £22,000
- Pitched roof extensions · from £24,500
- Single-storey rear extensions · from £23,500
- Flat roof extensions · from £23,500
- Glass box extensions · from £33,500
- Double-storey extensions · from £42,500
- Extension plans and drawings · from £1,300
- Planning permission for extensions · from £350
- Kitchen extensions · from £30,000
- Bungalow extensions · from £29,000
- Side extensions · from £24,500
- Orangery extensions · from £33,500
- Utility and boot room extensions · from £15,500
- Bedroom extensions · from £29,000
- Wraparound extensions · from £40,000
- Home office extensions · from £17,500
- Building regulations for extensions · from £1,000
- Side return extensions · from £20,000
- Timber frame extensions · from £23,500
- Porch extensions · from £4,450
- Extensions over a garage · from £26,500
Free site visit
A designer visits, takes measurements and photos, and discusses layouts, budget and timing with you.
Design and approvals
Once the layout is agreed, we deal with the council: planning permission or written confirmation that none is needed, plus building control.
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
Our team builds the extension, keeps you updated weekly and finishes with building control sign-off.
Questions about extensions in Bletchley
How much does an extension cost in Bletchley?
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 I need planning permission for an extension in Bletchley?
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.
Can I get a price before anyone visits?
Yes. This page shows guide prices adjusted for Bletchley, and the guide-price tool gives a range for your own size and finish in about a minute.
Book a free site visit in Bletchley
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.