What is a side extension?
A side extension builds into the space beside a semi-detached or detached house, often over a driveway or side passage. It can be single-storey, for a utility room, downstairs toilet or study, or two-storey to add a bedroom above.
How much does a side extension cost in Aylesbury?
In Aylesbury, a side extension typically costs £1,900–£2,950 per m² of floor area, including VAT at 20% (standard rate). For a typical 28 m² project that is roughly £53,000–£82,500. That range is adjusted for the South East, where domestic building work typically costs around 12% above the national average. Design, structural calculations and council fees are extra.
| Size or type | Guide range |
|---|---|
| Smaller project (20 m²) | £38,000–£59,000 |
| Typical project (28 m²) | £53,000–£82,500 |
| Larger project (39 m²) | £74,000–£115,000 |
| Rate per m² | £1,900–£2,950 |
What moves the price most:
- Drains, gas meters or soil pipes that need moving
- Steel work where the side wall is opened
- Single or two storeys
- Boundary walls and access for materials
A guide range is only a starting point: the guide price tool gives an instant figure for your size, and a free survey turns it into a fixed quote.
Do you need planning permission for a side extension in Aylesbury?
Before anything is built in Aylesbury, we confirm which approvals apply in England. In England a single-storey side extension can be permitted development if it is no more than 4 metres high and no wider than half the width of the original house. Side extensions of more than one storey always need planning permission, as do side extensions in conservation areas, National Parks and National Landscapes.
Where work involves a shared wall, building on the boundary, or digging foundations within 3 metres of a neighbour’s building and deeper than its foundations (or within 6 metres for deeper work), the Party Wall etc. Act 1996 applies and notices must be served before work starts.
At the survey we check your house’s planning history and any restrictions, and tell you which route applies.
What we handle
From survey to sign-off, the job normally involves:
- Survey of the boundary, drains and access
- Building control completion
- Opening into the existing house
- Electrics, heating and plastering
- Planning drawings and application
- Walls, roof and windows to match the house
How long does it take?
The build itself usually takes 10 to 16 weeks on site depending on size and storeys. Design and approvals come first and typically take 3 to 4 months, depending on the approval route.
Building in Aylesbury
The South East has a broad mix of housing, from Victorian terraces in the towns to post-war semis and newer estates, so extension types vary street by street.
If your home is in Aylesbury or close by in Leighton Buzzard, Berkhamsted and Chesham, a free home visit is the first step.
How it works
- 01
Survey and brief
We visit, discuss your ideas and budget, and survey the property or site at no cost.
- 02
Drawings and written quote
We prepare the design and give you a written, itemised quote with inclusions and exclusions.
- 03
Permissions sorted
Applications, building control and neighbour arrangements, all before the start date.
- 04
Build and sign-off
We run the build to a written programme and hand over the completion certificate.
Questions about side extensions in Aylesbury
Will I lose my driveway?
A side extension often takes the side drive. We look at whether parking can be kept at the front and whether a dropped kerb is needed.
Can I build a side extension without planning permission?
In England a single-storey side extension can be permitted development if it is no more than 4 metres high and no wider than half the original house, and the house is not in a conservation area or similar protected land. Two-storey side extensions always need planning permission.
How long does a side extension take in Aylesbury?
Typically 10 to 16 weeks on site depending on size and storeys. Design and approvals beforehand usually take 3 to 4 months.
Will a two-storey side extension look odd?
Not if it is designed well. Setting it back from the front and keeping the roof lower than the main ridge usually gives a natural look and is what most councils ask for.
How much does a side extension cost in Aylesbury?
In Aylesbury, a side extension typically costs £1,900–£2,950 per m² of floor area, including VAT at 20% (standard rate). A typical 28 m² project comes to roughly £53,000–£82,500. Your fixed price depends on the survey and drawings.