Two-storey extensions in Harrow
Everything for a two-storey extension in Harrow, in one place: types, guide prices for London, the approval rules in England and how to get started.
Harrow at a glance
- Postcode districts
- HA1
- Area
- Greater London, England
- Price region
- London
- Nearest towns
- Harrow on the Hill (0.5 miles), Wealdstone (1.5 miles), Sudbury (Greater London) (1.6 miles), Brent (2.2 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.
We cover postcode district HA1 in and around Harrow, along with neighbouring Harrow on the Hill, Wealdstone and Sudbury (Greater London).
Extensions available in Harrow
Two-storey rear extensions
For homes in Harrow: typical guide from £67,000.
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Two-storey side extensions
Harrow guide price from £103,500, Standard spec.
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Two-storey wraparound extensions
From £144,500 in Harrow. Free visit to firm it up.
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Part single, part two-storey extensions
From £86,500 in Harrow. Free visit to firm it up.
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Extensions over a garage
Guide from £38,000 in Harrow, including VAT.
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First-floor extensions
Harrow guide price from £30,000, Standard spec.
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Two-storey extensions for semi-detached houses
Design, approvals and build for Harrow homes. Guide from £67,000.
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Two-storey extensions for detached houses
Design, approvals and build for Harrow homes. Guide from £103,500.
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Kitchen extensions with bedrooms above
Guide from £67,000 (before kitchen units) in Harrow, including VAT.
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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?
Rear and side extensions suit most semi-detached and detached houses with room around them. Terraced and town-centre homes can take a two-storey extension too, with more care over neighbours, light and access.
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 Harrow
Harrow 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 Harrow
Do you cover Harrow?
Yes. We cover Harrow (HA1) and the surrounding area, including Harrow on the Hill and Wealdstone. The first site visit is free.
What does a two-storey extension cost in Harrow?
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 Harrow do you cover?
Everywhere around it, including Harrow on the Hill (0.5 miles), Wealdstone (1.5 miles) and Sudbury (Greater London) (1.6 miles), and the rest of Greater London.