Milton Keynes, Buckinghamshire
Semi-detached rear extension in Milton Keynes
Single or two-storey extensions for semi-detached houses, with side access and one party wall. If you live in Milton Keynes and want to know what a semi-detached rear extension would cost and whether it needs planning, start with the online guide price or a free site visit.
Milton Keynes is covered from our Buckinghamshire round, including MK3, MK4, MK5 and MK6. In Milton Keynes we measure the attached neighbour's extension at the survey, because it often sets the sensible depth for yours.
Book a free site visit
Tell us about the house and we'll call to arrange a free, no-obligation visit.
How much does a semi-detached rear extension cost in Milton Keynes?
A semi-detached rear extension in Milton Keynes is priced at £2,130–£3,470 per square metre including VAT as a guide, before kitchen fit-out and fees. South East prices run above our West Midlands baseline, mainly on labour rates and clay-soil foundations.
| Size | Guide price inc VAT |
|---|---|
| 3 m wide × 4 m deep (12 m²) | £25,500–£41,500 |
| 4 m wide × 5 m deep (20 m²) | £42,500–£69,500 |
| 4 m wide × 6 m deep (24 m²) | £51,000–£83,500 |
We put a fixed price in writing once the design is agreed, and explain any provisional sums such as foundations.
Do you need planning permission for a semi-detached rear extension in Milton Keynes?
Here is how the rules in England apply to a semi-detached rear extension in Milton Keynes.
Under England's householder permitted development rules you can usually add 3 metres at the back of an attached house, or 4 metres on a detached house, without a planning application, as long as the extension stays under 4 metres high and its eaves stay under 3 metres where it is within 2 metres of a boundary.
A two-storey rear extension can be permitted development in England only if it projects no more than 3 metres, stays at least 7 metres from the rear boundary, matches the existing roof pitch and has obscure-glazed upper side windows. In practice most double-storey rear extensions go through a householder planning application.
If 3 or 4 metres is not enough, England's prior approval route allows 6 metres on a terraced or semi-detached house and 8 metres on a detached house for a single-storey rear extension. Neighbours are consulted, the council decides within 42 days, and the fee is £249, rising to £310 from 8 December 2026.
Conservation areas, National Parks, National Landscapes and the Broads restrict permitted development, and listed buildings always need listed building consent. Before any drawing we look up the property's history with the council, because earlier extensions and removed rights change the answer.
What are homes in Milton Keynes like to extend?
Commuter semis and detached houses make up much of Milton Keynes, and longer gardens make England's prior approval route for deeper rear extensions worth considering.
How a semi-detached rear extension in Milton Keynes comes together
Survey visit
We visit free of charge, measure up, check access, drainage and neighbours' extensions, and note what you want the room to do.
Drawings and budget
Floor plans and elevations for the options, each with a guide price.
Planning and regulations
We take the design through the right planning route, then produce the construction drawings and engineer's calculations for building control.
Written price, then build
Once the design and approvals are in place, you get a fixed written price and programme, and we build through to sign-off.
Semi-detached rear extensions near Milton Keynes
Neighbouring places we cover include Newport Pagnell (3.5 miles) and Bletchley (3.5 miles).
- Semi-detached rear extension in Newport Pagnell
- Semi-detached rear extension in Bletchley
- Semi-detached rear extension in Leighton Buzzard
- Semi-detached rear extension in Buckingham
- Semi-detached rear extension in Ampthill
Other work in Milton Keynes:
FAQ
Semi-detached rear extension questions in Milton Keynes
Can I live at home while the extension is built?
Usually yes. Most of the work is outside until the back wall is opened near the end, and that stage is screened off.
Do I need a party wall agreement?
In England, usually yes if the extension is on or near a shared boundary or the foundations are close to a neighbour's building. We serve the notices.
How long does a semi extension take?
10 to 16 weeks on site for a single-storey extension.
How much does a semi-detached rear extension cost in Milton Keynes?
As a guide, £2,130–£3,470 per square metre including VAT for a standard specification. For example, 3 m wide × 4 m deep (12 m²): about £25,500–£41,500 at that rate. Your written price follows the survey.
Do I need planning permission for a rear extension in Milton Keynes?
Often not for a single-storey rear extension of up to 3 metres (4 metres on a detached house) under permitted development, or up to 6 or 8 metres with prior approval, unless the house is in a conservation area or its rights have been removed.
What postcode areas do you cover around Milton Keynes?
Including MK3, MK4, MK5, MK6, MK10 and MK13, and the surrounding Buckinghamshire area.