Two-storey extensions in St Helier
From over-garage bedrooms to full wraparounds, we cover every kind of two-storey extension in St Helier.
St Helier at a glance
- Postcode districts
- SM4
- Area
- Greater London, England
- Price region
- London
- Nearest towns
- Carshalton (1.2 miles), Morden (1.3 miles), Mitcham (1.6 miles), Wallington (1.8 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.
We cover postcode district SM4 in and around St Helier, along with neighbouring Carshalton, Morden and Mitcham.
Extensions available in St Helier
Two-storey rear extensions
Design, approvals and build for St Helier homes. Guide from £67,000.
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Two-storey side extensions
Guide from £103,500 in St Helier, including VAT.
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Two-storey wraparound extensions
From £144,500 in St Helier. Free visit to firm it up.
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Part single, part two-storey extensions
Design, approvals and build for St Helier homes. Guide from £86,500.
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Extensions over a garage
St Helier guide price from £38,000, Standard spec.
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First-floor extensions
Design, approvals and build for St Helier homes. Guide from £30,000.
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Two-storey extensions for semi-detached houses
St Helier guide price from £67,000, Standard spec.
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Two-storey extensions for detached houses
For homes in St Helier: typical guide from £103,500.
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Kitchen extensions with bedrooms above
Our London guide starts at £67,000 (before kitchen units) for this type.
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Extra bedroom and en-suite extensions
St Helier guide price from £67,000 (plus en-suite), Standard spec.
Learn moreWhich type suits your house?
Which type suits your house in St Helier 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 Helier
St Helier 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 Helier
Do you cover St Helier?
Yes. We cover St Helier (SM4) and the surrounding area, including Carshalton and Morden. The first site visit is free.
What does a two-storey extension cost in St Helier?
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 Helier do you cover?
Everywhere around it, including Carshalton (1.2 miles), Morden (1.3 miles) and Mitcham (1.6 miles), and the rest of Greater London.