Extra bedroom and en-suite extensions in Milton Keynes
We cover Milton Keynes and the rest of Buckinghamshire for extra bedroom and en-suite extensions. Start with a free site visit and a plain-English view of what your house and plot can take.
Milton Keynes: the key facts for this kind of project.
- Postcode districts
- MK5, MK6, MK8, MK9, MK10, MK11 and nearby districts
- County / area
- Buckinghamshire, England
- Price region
- South East England
- Guide price
- £61,500–£83,000 (£2,200–£2,970 per m²), plus £5,500–£11,000 for the en-suite
- 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 an extra bedroom and en-suite extension
An extra bedroom and en-suite extension is a two-storey extension planned around a new double bedroom with its own shower room on the first floor, with a ground-floor room below. It is one of the most effective ways to add space for a growing family. Nationwide's 2025 research linked adding a double bedroom and bathroom to a three-bed, one-bathroom house with value gains of up to 24%.
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 an extra bedroom and en-suite extension is set by its size and specification. For Milton Keynes and the rest of South East England, our guide is £2,200–£2,970 per m² including VAT, so about £61,500–£83,000 (plus £5,500–£11,000 for the en-suite) for a 4 m × 3.5 m footprint on two floors (28 m² of new floor space). Professional fees for drawings and the structural engineer are listed separately on our prices page.
| Spec | Per m² | A 4 m × 3.5 m footprint on two floors (28 m² of new floor space) |
|---|---|---|
| Essential | £2,020–£2,730 per m² | £56,500–£76,500 |
| Standard | £2,200–£2,970 per m² | £61,500–£83,000 |
| Premium | £2,640–£3,560 per m² | £74,000–£100,000 |
Planning and building regulations in Milton Keynes
In England, an extra bedroom extension at the rear can be permitted development if it goes no more than 3 m beyond the original rear wall and stays 7 m from the rear boundary. Upper side windows, including en-suite windows, must be obscure-glazed and non-opening below 1.7 m. Side or deeper designs 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
Sound and privacy
Bedrooms above a kitchen or family room benefit from an insulated floor to reduce noise. Side-facing upstairs windows usually have to be obscure-glazed, so we place the main bedroom window to the rear and the en-suite window to the side where possible.
Connecting to the landing
The new bedroom must be reached from the existing landing, usually through a new opening in the outside wall or by taking part of an existing bedroom as a corridor. We look at the stairs and landing first, because a poor connection can waste much of the new space.
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.
Choose the approval route
Some designs fit permitted development, most need a householder application. We decide which applies in England before drawing in detail.
Price it properly
Once the engineer's calculations are in, we fix the build price in writing, with a clear list of what's included.
Finish and certify
Second fix, plastering and making good, then building control's final inspection and the completion paperwork.
Questions about extra bedroom and en-suite 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.
How much does an extra bedroom and en-suite extension cost in Milton Keynes?
Our guide for South East England, which covers Milton Keynes, is £2,200–£2,970 per m² including VAT. A typical project with a 4 m × 3.5 m footprint on two floors (28 m² of new floor space) comes to about £61,500–£83,000 (plus £5,500–£11,000 for the en-suite). Design and approval fees are extra, and we fix the build price in writing once the design is agreed.
Do I need planning permission for an extra bedroom and en-suite 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.
Can an en-suite go in a room with no window?
Yes. A shower room without a window is allowed, provided it has a mechanical extract fan to the outside that meets Part F. Many people prefer a window for daylight, but if it faces a neighbour it will usually need obscure glass. We plan the extract route early so the duct is hidden.
How big should a new double bedroom be?
There is no legal minimum size for a bedroom in a house you own, so the test is whether it works. A comfortable double needs room for the bed with space to walk round it, wardrobes and a door that opens freely. We draw furniture on the plans so you can judge the space before anything is built.
Nearby
Nearby towns we cover for extra bedroom and en-suite extensions:
Other extensions in Milton Keynes
All two-storey extension services in Milton Keynes · Extra bedroom and en-suite 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.