Single Storey Extensions in Milton Keynes

A single storey extension in Milton Keynes typically costs £2,400–£3,200 per m² finished ready for decoration — roughly £29,000–£38,500 for a 12m² rear extension, with any kitchen fit-out priced separately. An extension in Milton Keynes needs building regulations approval — Milton Keynes City Council’s 2026 scheme of charges lists a 10–40m² extension at £700 plus VAT (£840) on full plans, or £769 plus VAT as a building notice; up to 10m² is £555 plus VAT. It either fits within permitted development or needs householder planning permission, which costs £548 from April 2026 and is decided within eight weeks.

Typical cost: £2,400–£3,200 per m²
Council: Milton Keynes City Council
Planning: Permitted development or £548 application
Building regulations: Needed
Ground: Slow-draining clay

Prices are our 2026 guide prices; your fixed price comes in writing after the free visit. Council fees checked October 2026.

Extensions in Milton Keynes

Extensions on Milton Keynes houses

Milton Keynes was designated a new town in January 1967, and most of it was built as grid-square estates set between grid roads about a kilometre apart. A lot of homes face onto open-plan frontages, wide verges, landscaped strips or redways rather than a walled front garden.

Most extensions we build here are single storey at the rear, matched to the existing brick or stone, with the drainage and any sewer nearby checked before the footings are dug.

We cover Milton Keynes (MK1–MK15) and the areas around it, including Bradwell, Great Linford, Shenley Church End, Willen, Woughton on the Green and Loughton. Travel does not change the price.

Milton Keynes specifically

Ground, drainage and conservation in Milton Keynes

The British Geological Survey maps most of the city on Kellaways beds and Oxford Clay under boulder clay. It drains slowly and shrinks and swells with the seasons — which is why the city was planned around balancing lakes such as Willen and Caldecotte. Clay shrinks and swells, so foundations go deeper — deeper again near trees — and building control confirms the depth on site.

The conservation areas here are the old village cores the city grew around — Bradwell, Great Linford, Milton Keynes Village, Shenley Church End and Willen among them. Outside those, normal householder permitted development applies unless your estate’s original planning permission removed it.

The Great Ouse and Ouzel corridors are kept as parkland flood plain, so most estates sit well away from river flood zones; on clay, surface water is usually the bigger issue. You can check any address on the Environment Agency flood map.

Sources: Milton Keynes conservation areas.

Milton Keynes City Council

Planning, building regulations and fees in Milton Keynes

Step 1Check whether it fits permitted development, and if you want certainty apply for a lawful development certificate (£274). Planning Portal: extensions
Step 2In the Milton Keynes conservation area, side extensions and rear extensions of more than one storey always need planning permission.
Step 3If permission is needed, apply for householder planning permission (£548 from April 2026), decided within eight weeks. Pre-application advice from Milton Keynes City Council costs £360 for a householder project (£180 for outbuildings), with a written reply within six weeks. Planning Portal: application fees
Step 4Apply for building regulations approval: Milton Keynes City Council’s 2026 scheme of charges lists a 10–40m² extension at £700 plus VAT (£840) on full plans, or £769 plus VAT as a building notice; up to 10m² is £555 plus VAT. Milton Keynes City Council: building regulation charges
Step 5If the extension is over or within 3m of a public sewer, check Anglian Water’s build-over criteria; a consultation costs £107. Anglian Water: building over or near our assets
Step 6We build to the approved drawings and work to the building control inspections at each stage.

Council fees and rules checked October 2026. Planning fees are the national fees from 1 April 2026.

What is included

Everything below is included in an extension

Drawings and the building control application
Foundations set from a trial hole, not a guess
Drainage diverted or rebuilt where it needs to be
Build-over and party wall matters flagged and handled
Roof and threshold junctions detailed properly
Electrics and plumbing by registered trades, with certificates
Building control sign-off at the end
A five year guarantee, in writing

Questions

Extensions in Milton Keynes: questions

How much does a single storey extension cost in Milton Keynes?

A single storey extension in Milton Keynes typically costs £2,400–£3,200 per m² finished ready for decoration — roughly £29,000–£38,500 for a 12m² rear extension, with any kitchen fit-out priced separately. Your fixed price comes in writing after the free visit.

How much does planning and building control cost for an extension in Milton Keynes?

Householder planning permission is £548 (from April 2026) if you need it, or £274 for a lawful development certificate. Milton Keynes City Council’s 2026 scheme of charges lists a 10–40m² extension at £700 plus VAT (£840) on full plans, or £769 plus VAT as a building notice; up to 10m² is £555 plus VAT.

Do I need planning permission for an extension in Milton Keynes?

Many single-storey rear extensions are permitted development within size limits. In the Milton Keynes conservation area, side extensions and rear extensions of more than one storey always need permission.

Is Milton Keynes in a conservation area?