Two-storey extensions in Friern Barnet
Everything for a two-storey extension in Friern Barnet, in one place: types, guide prices for London, the approval rules in England and how to get started.
Friern Barnet at a glance
- Postcode districts
- N11 and N12
- Area
- Greater London, England
- Price region
- London
- Nearest towns
- Muswell Hill (1.7 miles), Finchley (1.8 miles), Wood Green (2 miles), Palmers Green (2.1 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 districts N11 and N12 in and around Friern Barnet, along with neighbouring Muswell Hill, Finchley and Wood Green.
Extensions available in Friern Barnet
Two-storey rear extensions
Guide from £67,000 in Friern Barnet, including VAT.
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Two-storey side extensions
Guide from £103,500 in Friern Barnet, including VAT.
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Two-storey wraparound extensions
Friern Barnet guide price from £144,500, Standard spec.
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Part single, part two-storey extensions
From £86,500 in Friern Barnet. Free visit to firm it up.
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Extensions over a garage
Friern Barnet guide price from £38,000, Standard spec.
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First-floor extensions
Our London guide starts at £30,000 for this type.
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Two-storey extensions for semi-detached houses
Friern Barnet guide price from £67,000, Standard spec.
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Two-storey extensions for detached houses
Our London guide starts at £103,500 for this type.
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Kitchen extensions with bedrooms above
Design, approvals and build for Friern Barnet homes. Guide from £67,000 (before kitchen units).
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Extra bedroom and en-suite extensions
For homes in Friern Barnet: typical guide from £67,000 (plus en-suite).
Learn moreWhich type suits your house?
The boundaries usually decide it. Two-storey work close to a neighbour needs careful design for light and privacy, so at the visit in Friern Barnet we measure distances to every boundary before suggesting a type.
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 Friern Barnet
Friern Barnet 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 Friern Barnet
Do you cover Friern Barnet?
Yes. We cover Friern Barnet (N11 and N12) and the surrounding area, including Muswell Hill and Finchley. The first site visit is free.
What does a two-storey extension cost in Friern Barnet?
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 Friern Barnet do you cover?
Everywhere around it, including Muswell Hill (1.7 miles), Finchley (1.8 miles) and Wood Green (2 miles), and the rest of Greater London.