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 Richmond?
In Richmond, a single-storey extension typically costs £2,550–£3,750 per m² of floor area, including VAT at 20% (standard rate). For a typical 20 m² project that is roughly £51,000–£75,000. That range is adjusted for London, where domestic building work typically costs around 30% above the national average. Design, structural calculations and council fees are extra.
| Size or type | Guide range |
|---|---|
| Smaller project (14 m²) | £35,500–£52,500 |
| Typical project (20 m²) | £51,000–£75,000 |
| Larger project (28 m²) | £71,500–£105,000 |
| Rate per m² | £2,550–£3,750 |
What moves the price most:
- How much of the existing house is opened up
- Floor area and the length of new wall
- Kitchen, flooring and finishes, which we can include or leave to you
- Glazing: sliding and bifold doors cost more than French doors
Your exact price depends on the survey and drawings. The guide price tool gives a quick range in the meantime.
Do you need planning permission for a single-storey extension in Richmond?
The approval route for Richmond 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.
If the answer is not clear-cut, we can apply for formal confirmation before you commit to the build.
What we handle
Handled as part of most single-storey extensions:
- Structural calculations for steels and lintels
- 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
- Building control inspections and completion certificate
How long does it take?
Allow 10 to 14 weeks on site for a typical rear extension, after approvals. Before that, surveys, drawings and approvals usually take 6 to 12 weeks, longer if the council asks for changes.
Building in Richmond
Victorian and Edwardian terraces dominate many London streets, which is why side return, wraparound and mansard projects are so common here.
From TW9 outwards, we take on projects throughout Richmond and the surrounding parts of Greater London.
How it works
- 01
Survey and brief
We visit, discuss your ideas and budget, and survey the property or site at no cost.
- 02
Design and pricing
Design options, then a fixed quote based on the chosen drawings and specification.
- 03
Permissions sorted
Applications, building control and neighbour arrangements, all before the start date.
- 04
Construction and completion
We build, put right any snags and hand over the building control certificate.
Questions about single-storey extensions in Richmond
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.
How long does a single-storey extension take?
Once approvals are in place, a typical rear extension takes 10 to 14 weeks on site. Design and approvals usually take another 6 to 12 weeks beforehand, depending on whether a planning application is needed.
How much does a single-storey extension cost in Richmond?
In Richmond, a single-storey extension typically costs £2,550–£3,750 per m² of floor area, including VAT at 20% (standard rate). A typical 20 m² project comes to roughly £51,000–£75,000. Your fixed price depends on the survey and drawings.
Who approves a single-storey extension in Richmond?
Planning matters in Richmond go to the council covering your address, and the work needs building control approval. We prepare and submit the applications for you.
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.