Two-storey extensions in St James's
We design, get approval for and build two-storey extensions in St James's and the surrounding area. Choose the type of extension below or book a free site visit.
St James's at a glance
- Postcode districts
- SW1Y, W1J, W1K and W1S
- Area
- Greater London, England
- Price region
- London
- Nearest towns
- Soho (0.5 miles), Westminster (0.7 miles), Holborn (1.1 miles), Knightsbridge and Belgravia (1.2 miles)
- Approvals
- Two-storey rear: up to 3 m deep and 7 m from the rear boundary under permitted development. Side, wraparound and front: planning permission.
Around St James's we also work in Soho, Westminster and Holborn, and across the rest of Greater London. Postcode districts in and near St James's: SW1Y, W1J, W1K and W1S.
Extensions available in St James's
Two-storey rear extensions
Design, approvals and build for St James's homes. Guide from £67,000.
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Two-storey side extensions
For homes in St James's: typical guide from £103,500.
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Two-storey wraparound extensions
For homes in St James's: typical guide from £144,500.
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Part single, part two-storey extensions
From £86,500 in St James's. Free visit to firm it up.
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Extensions over a garage
From £38,000 in St James's. Free visit to firm it up.
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First-floor extensions
Design, approvals and build for St James's homes. Guide from £30,000.
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Two-storey extensions for semi-detached houses
For homes in St James's: typical guide from £67,000.
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Two-storey extensions for detached houses
St James's guide price from £103,500, Standard spec.
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Kitchen extensions with bedrooms above
Design, approvals and build for St James's homes. Guide from £67,000 (before kitchen units).
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Extra bedroom and en-suite extensions
Our London guide starts at £67,000 (plus en-suite) for this type.
Learn moreWhich type suits your house?
Which type suits your house in St James's depends mostly on where you have room. A deep garden points to a rear extension; space beside the house points to a side or over-garage extension; a house that already has a single-storey extension can often take a first floor on top.
Also available in Greater London
- Two-storey front extensions
- Two-storey extensions for end-of-terrace houses
- Two-storey annexe extensions
- Garage conversions with a room above
- Two-storey extension plans and drawings
- Planning permission for two-storey extensions
- Structural engineering for two-storey extensions
- Building regulations for two-storey extensions
- Party wall notices for extensions
- Design and build two-storey extensions
Rules for St James's
St James's is in England. Two-storey rear: up to 3 m deep and 7 m from the rear boundary under permitted development. Side, wraparound and front: planning permission. 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.
The full England rules explained
Questions about extensions in St James's
Do you cover St James's?
Yes. We cover St James's (SW1Y, W1J, W1K and W1S) and the surrounding area, including Soho and Westminster. The first site visit is free.
What does a two-storey extension cost in St James's?
Using our London guide, a two-storey rear extension with a 4 m × 3.5 m footprint on two floors (28 m² of new floor space) is about £67,000–£90,500 including VAT. An extension over a garage is about £38,000–£55,000.
Which other places near St James's do you cover?
Everywhere around it, including Soho (0.5 miles), Westminster (0.7 miles) and Holborn (1.1 miles), and the rest of Greater London.