Part single, part two-storey extensions in Milton Keynes
If you live in Milton Keynes and need more room without moving, a part single, part two-storey extension is worth a serious look. We handle the drawings, approvals, structure and build.
Useful details for planning a part single, part two-storey extension in Milton Keynes.
- Postcode districts
- MK5, MK6, MK8, MK9, MK10, MK11 and nearby districts
- County / area
- Buckinghamshire, England
- Price region
- South East England
- Guide price
- £79,000–£109,000 (£2,200–£3,030 per m²)
- Approval route
- It may be permitted development if it goes no more than 3 m beyond the original rear wall (counting any single-storey part) and stays 7 m from the rear boundary; otherwise it needs planning permission.
- Nearest towns
- Newport Pagnell (3.5 miles), Bletchley (3.5 miles), Leighton Buzzard (9.6 miles)
- First visit
- Free, no obligation
About a part single, part two-storey extension
A part single, part two-storey extension suits you if you want a generous ground floor but only need one extra room upstairs, or if a full two-storey design would affect a neighbour too much. You get design options that test where the two-storey part works best, the approvals your nation needs, structural design, building regulations approval and the build, carried out by vetted teams working under S&K.
We cover Milton Keynes (MK5, MK6, MK8, MK9, MK10, MK11 and nearby districts) and the places around it, including Newport Pagnell (3.5 miles), Bletchley (3.5 miles) and Leighton Buzzard.
What it costs in Milton Keynes
Most of the cost of a part single, part two-storey extension is set by its size and specification. For Milton Keynes and the rest of South East England, our guide is £2,200–£3,030 per m² including VAT, so about £79,000–£109,000 for a 6 m × 4 m ground floor and a first floor over half of it (36 m² in total). Steelwork for wide openings is the item most likely to move the figure; we'll know once the engineer has designed it.
| Spec | Per m² | A 6 m × 4 m ground floor and a first floor over half of it (36 m² in total) |
|---|---|---|
| Essential | £2,020–£2,780 per m² | £73,000–£100,000 |
| Standard | £2,200–£3,030 per m² | £79,000–£109,000 |
| Premium | £2,640–£3,630 per m² | £95,000–£130,500 |
Planning and building regulations in Milton Keynes
In England, the extension can only be permitted development if it goes no more than 3 m beyond the original rear wall and stays at least 7 m from the rear boundary, with matching materials and roof pitch. We check the whole design against the rules, including the 50% garden coverage limit. If any part fails, or extends beyond a side wall on two floors, you need planning permission, costing £548 (or £575 for applications made from 8 December 2026).
Approval in England: Householder planning application: £548 (or £575 for applications made from 8 December 2026). Lawful development certificate: £274 (about £288 for applications from 8 December 2026). Councils should decide householder applications within 8 weeks of validation.
Building regulations: Building regulations approval (full plans recommended) from the council or a registered building control approver, with a completion certificate at the end.
Design points for Milton Keynes homes
Where to put the two-storey part
The two-storey section usually works best away from the closest neighbour, with the single-storey part on that boundary side. We test a few positions against neighbours' windows, the upstairs layout and the roof shape before choosing the one to take forward.
Structure at the step
The first-floor wall above often sits over the new open-plan space, so it needs a steel beam or frame to carry it. Loads come down at different points than in a full two-storey design, and the engineer sizes the foundations to suit each part.
How we'd run your project
Measure and listen
A visit to Milton Keynes to understand how you live in the house now and what the extra rooms need to do, plus a first look at the structure.
Design and approvals
We draw the extension and check it against the rules for England, then apply for planning permission or a certificate of lawfulness, whichever fits.
Technical design
We prepare the building regulations drawings, structural calculations and specification so the build price can be fixed.
Build
Foundations, walls, floor, roof, windows, then first and second fix. We break through into the house as late as we can.
Questions about part single, part two-storey extensions in Milton Keynes
Which postcodes do you cover around Milton Keynes?
We cover Milton Keynes (MK5, MK6, MK8, MK9, MK10, MK11 and nearby districts) and nearby places including Newport Pagnell, Bletchley and Leighton Buzzard, plus the rest of Buckinghamshire. The first site visit is free.
Do I need planning permission for a part single, part two-storey extension in Milton Keynes?
Milton Keynes is in England, so England planning rules apply. It may be permitted development if it goes no more than 3 m beyond the original rear wall (counting any single-storey part) and stays 7 m from the rear boundary; otherwise it needs planning permission. If in doubt, a lawful development certificate or a planning application gives you certainty before you build.
Who handles building regulations for a project in Milton Keynes?
We handle it as part of the project. What's needed in England: building regulations approval (full plans recommended) from the council or a registered building control approver, with a completion certificate at the end. We prepare the drawings and the engineer's calculations, book the inspections and pass you the completion paperwork at the end.
Can I add roof lights to the single-storey part?
Yes. Roof lights or a lantern over the single-storey part are one of the main reasons to choose this design, as they light the middle of a deep kitchen. In England they count towards the Part L glazing allowance, normally 25% of the new floor area plus windows removed, so we balance them with the rear doors.
Which side should the two-storey part go on?
Usually the side furthest from the nearest neighbour's windows, so the single-storey part sits nearest them and keeps their light. Other factors are where the stairs land upstairs, which room needs the extra space and where drains run. We sketch options at the design stage and explain which is most likely to be approved.
Nearby
Other towns near Milton Keynes:
Other extensions in Milton Keynes
- Rear
- Side
- Wraparound
- Over a garage
- First floor
- Semi-detached
- Detached
- Kitchen and bedrooms
- Bedroom and en-suite
All two-storey extension services in Milton Keynes · Part single, part two-storey extensions across Buckinghamshire
Send us your postcode and a few details. We'll get back to you to arrange a visit and talk through your options.