A double-storey extension adds two floors of new space to your house in one build, typically a larger kitchen or living room downstairs with an extra bedroom, bathroom or en-suite above, sharing one set of foundations and one roof.
Whatever type of house you own in Milton Keynes, we start by looking at how a double-storey extension would fit it rather than offering a standard package. We cover MK5, MK6, MK9 and MK13 and neighbouring places such as Bletchley, Leighton Buzzard and Ampthill. One named person looks after you from survey to handover, and nothing is booked until you hold our figure in writing, fixed for the work described.
- Guide price
- £67,000–£134,000 inc VAT
- Time on site
- 14–22 weeks on site
- Postcodes
- MK5, MK6, MK9, MK13 and MK14
- Planning rules
- England
- Local area
- Buckinghamshire
- Survey
- Free, with a written quote
What should you budget for a double-storey extension in Milton Keynes?
Below is a breakdown of typical costs for a double-storey extension in Milton Keynes. Because rates in the South East are about 12% above the national guide, the overall guide comes to £67,000–£134,000, including VAT. Size, materials and access move the figure, and a free-of-charge survey settles it.
| Type of job | What it usually involves | Guide in Milton Keynes |
|---|---|---|
| Small (15–20m² total) | A compact rear or side extension adding a small room on each floor. | £45,000–£73,000 |
| Typical (30–40m² total) | A larger kitchen or living room below with a double bedroom or en-suite above. | £67,000–£134,000 |
| Large (50m² plus total) | Wide or deep extensions, often with a new bathroom, steelwork and high-spec glazing. | £112,000–£202,000 |
What moves the price up or down:
- Combined floor area across both storeys
- How the new roof joins the existing roof
- Bathrooms, en-suites and plumbing on the upper floor
- Scaffolding duration, access and the level of finishes
What’s included?
- Insulated cavity walls with brick or render to match the house
- First-floor joists, stud walls and new openings upstairs
- Roof structure tied into the existing roof, tiled to match
- Electrics, plumbing and heating by qualified trades, with certificates
- Windows, external doors, plastering and internal doors
- Building control inspections and completion certificate
Local housing and a double-storey extension
Buckinghamshire runs from Chiltern villages of brick and flint, through Metroland interwar semis around Amersham and Chesham, to Victorian terraces in High Wycombe and Aylesbury. Milton Keynes adds estates built from the 1970s onwards in brick, render and timber frame, and new housing continues to spread around its edges.
Chiltern cottages may need lime repairs and careful window choices in conservation areas. Interwar semis suit hip-to-gable lofts and rear extensions, while Milton Keynes homes often need roofline renewal, replacement doors and garage conversions.
Knowing the typical building types in Buckinghamshire helps, but a survey of your own home in Milton Keynes is what decides the right approach to a double-storey extension.
Do you need permission in Milton Keynes?
For anyone in Milton Keynes, the relevant framework is England's. The summary below is general, so we always contact the council about your address before putting a price in writing.
In England, a two-storey rear extension can only be permitted development if it is no more than 3 m deep, at least 7 m from the rear boundary and finished to match the house. Most double-storey and all two-storey side extensions need full planning permission.
Building Regulations approval is needed, with structural calculations for beams, foundations and the roof. The Party Wall etc. Act 1996 often applies on semi-detached and terraced houses.
Rules change and every property is different, so we check the planning history and constraints for your address before we quote.
From survey to handover
Free site survey
It starts with a survey at the property, free of charge. We check condition, access and services, ask how you want the finished result to look, and answer any questions you have about a double-storey extension.
Your fixed price
The quote arrives in writing, not over the phone. It covers the full scope, the finishes you've chosen, any exclusions and the payment schedule, with a fixed price tied to that specification.
Getting ready
Before anyone starts, we confirm the programme in writing, check whether consents are required and arrange deliveries. If a skip or scaffolding on the road needs a permit, we apply for it.
On site to finish
Work goes ahead as scheduled and you deal with one contact throughout. When the last trade leaves, we clear and clean the site, talk you through what has been done and pass on any certificates and care instructions.
Working with SK Home Improvements
Questions about a double-storey extension in Milton Keynes
How long does a double-storey extension take?
A double-storey extension typically takes 14–22 weeks on site, depending on size, roof design and weather. Foundations and ground-floor walls come first, then the first-floor joists, upper walls and roof. Once it is weathertight, electrics, plumbing, plastering and finishes follow. Allow extra time beforehand for drawings, calculations and approvals. We give you a stage-by-stage programme with your quote.
Is a double-storey extension better value than single-storey?
A double-storey extension usually gives better value per square metre than a single-storey one, because the same foundations and roof serve twice the floor area. The overall cost is higher, and planning can be harder because of the effect on neighbours. If you might want an extra bedroom later, building both floors now avoids a second round of disruption and scaffolding.
Do I need planning permission in Milton Keynes?
It depends on the work, the size of the project, your property type and whether the building is listed or in a conservation area. Milton Keynes is in England, so England's rules apply. Many smaller jobs need no planning application, but some still need building control approval. We check what applies to your address before quoting.
Can I stay at home during the work?
In most cases, yes. Most people can live at home throughout, and we plan the work to keep disruption down by protecting floors, agreeing working hours and keeping access routes clear. Bigger jobs affecting kitchens, bathrooms or heating may mean a short spell with reduced facilities, and we talk this through with you at the survey.
Can the new upstairs room have its own bathroom?
A new upstairs room can usually have an en-suite, provided waste pipes can reach the soil stack or a new one can be installed. Running the waste pipe to the right falls is the main design question, and a pumped system is an option where gravity will not work. We plan bathroom positions at the design stage so pipes, ventilation and insulation are built in rather than added later.
Also covering areas around Milton Keynes
Milton Keynes and its MK5, MK6, MK9 and MK13 postcodes are part of our coverage. Homeowners in Bletchley, Leighton Buzzard and Ampthill can also book a free survey with us and receive a written price for their job.