What is a single-storey extension?
A single-storey extension is a ground-floor addition, usually at the rear of a house, that enlarges a kitchen, living or dining space. Most are built with cavity walls on concrete foundations and finished with a flat roof and roof lantern or a pitched tiled roof.
How much does a single-storey extension cost in Eastleigh?
In Eastleigh, a single-storey extension typically costs £2,200–£3,250 per m² of floor area, including VAT at 20% (standard rate). For a typical 20 m² project that is roughly £44,000–£65,000. Prices across the South East are typically 12% above the UK average for this kind of work, which is reflected in the range for Eastleigh. Design, structural calculations and council fees are extra.
| Size or type | Guide range |
|---|---|
| Smaller project (14 m²) | £31,000–£45,500 |
| Typical project (20 m²) | £44,000–£65,000 |
| Larger project (28 m²) | £61,500–£91,000 |
| Rate per m² | £2,200–£3,250 |
The biggest cost drivers are:
- Glazing: sliding and bifold doors cost more than French doors
- Roof type and the size of any lantern or roof windows
- Kitchen, flooring and finishes, which we can include or leave to you
- Ground conditions and foundation depth
Use the guide price tool to see how size and specification change the figure, then ask for a written, itemised quote.
Do you need planning permission for a single-storey extension in Eastleigh?
The approval route for Eastleigh is set by planning law in England. In England a single-storey rear extension is often permitted development: broadly up to 3 metres deep on a semi-detached or terraced house and 4 metres on a detached house, no higher than 4 metres, with eaves no higher than 3 metres within 2 metres of a boundary, and covering no more than half the garden. The larger home extension scheme allows up to 6 or 8 metres if you notify the council first and neighbours have a chance to comment. In conservation areas, National Parks and National Landscapes the larger home extension route, side extensions and cladding are not permitted development. Flats and houses whose rights have been removed need a planning application, and listed buildings need listed building consent.
Building regulations approval comes from the council’s building control service or a registered building control approver. The work is inspected at key stages, such as foundations, drainage and insulation, and a completion certificate is issued at the end.
At the survey we check your house’s planning history and any restrictions, and tell you which route applies.
What we handle
Handled as part of most single-storey extensions:
- First and second fix electrics, heating and plastering
- Cavity walls, insulation and roof to current building regulations
- Foundations, drainage and any build-over agreement
- Knock-through to the existing house with steel beams
- Doors, windows and roof glazing installed
- Structural calculations for steels and lintels
How long does it take?
The build itself usually takes 10 to 14 weeks on site for a typical rear extension, after approvals. Design and approvals come first and typically take 6 to 12 weeks, depending on the approval route.
Building in Eastleigh
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.
We work across Eastleigh and neighbouring areas such as Southampton, Winchester and Totton. Postcodes we cover in Eastleigh include SO50 and SO97.
How it works
- 01
Visit and measured survey
A free visit to understand the project, check access and take measurements.
- 02
Design and fixed quote
Drawings, structural calculations and an itemised, fixed price for the agreed specification.
- 03
Approvals in place
We handle planning, building control and neighbour notices before work starts.
- 04
Build and sign-off
We run the build to a written programme and hand over the completion certificate.
Questions about single-storey extensions in Eastleigh
How much does a single-storey extension cost in Eastleigh?
In Eastleigh, a single-storey extension typically costs £2,200–£3,250 per m² of floor area, including VAT at 20% (standard rate). A typical 20 m² project comes to roughly £44,000–£65,000. Your fixed price depends on the survey and drawings.
Can I stay in the house during the build?
Usually yes. We build the shell before opening up the back wall, so the house stays weathertight for most of the job. There will be a few weeks when the kitchen or back room is out of use.
What is a build-over agreement?
If a public sewer runs within 3 metres of the extension, the water company normally has to agree to the work before it starts. We check sewer records during design and apply where needed.
How long does a single-storey extension take in Eastleigh?
Typically 10 to 14 weeks on site for a typical rear extension, after approvals. Design and approvals beforehand usually take 6 to 12 weeks.
Is VAT charged on an extension?
Yes. Building work on an existing home is standard-rated, so VAT at 20% applies. Our guide prices include it.