Single Storey Extensions in Bletchley | Building Control Handled

A single storey extension in Bletchley 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 Bletchley 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 Bletchley

Extensions on Bletchley houses

Bletchley grew fast as a London overspill town after a 1952 agreement with five London boroughs — from about 11,000 people in 1951 to over 30,000 by 1971 — so much of it is post-war brick semis and terraces, around an older core at Old Bletchley and Church Green and newer estates such as Newton Leys.

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 Bletchley (MK1–MK3) and the areas around it, including Fenny Stratford, Far Bletchley, Water Eaton, Denbigh, Newton Leys, West Bletchley, Newton Longville and Simpson. Travel does not change the price.

Bletchley specifically

Ground, drainage and conservation in Bletchley

Bletchley is Oxford Clay country — the clay that fed the local brickworks until 1990. It drains slowly and moves with the seasons, so soakaways rarely work well and anything built near trees needs deeper foundations. Clay shrinks and swells, so foundations go deeper — deeper again near trees — and building control confirms the depth on site.

The Bletchley Conservation Area covers Bletchley Park, Old Bletchley and St Mary’s Church around Church Green. Its review favours keeping historic brick and stone walls with their copings and discourages close-boarded fencing and metal railings on boundaries.

The River Ouzel runs along the east side. Milton Keynes City Council’s 2024 flood risk assessment records river flooding affecting properties in Bletchley and Water Eaton, and Bletchley is a designated surface-water flood risk area. You can check any address on the Environment Agency flood map.

Sources: Bletchley Conservation Area review.

Milton Keynes City Council

Planning, building regulations and fees in Bletchley

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 Bletchley 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 Bletchley: questions

How much does a single storey extension cost in Bletchley?

A single storey extension in Bletchley 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 Bletchley?

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 Bletchley?

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

Is Bletchley in a conservation area?