Friern Barnet house extensions
Looking to extend your home in Friern Barnet? Start here: extension types, guide prices for Friern Barnet, the planning rules that apply and how a project runs.
- Postcode districtsN2, N3, N10, N11, N12, N20
- Price regionLondon (×1.3)
- Planning rulesEngland
- Site visitFree, no obligation
Where we work near Friern Barnet
Postcode districts we cover around Friern Barnet include N2, N3, N10, N11, N12, N20. Neighbouring towns we cover include Muswell Hill (2 miles), Finchley (2 miles), Wood Green (2 miles), Palmers Green (2 miles), East Barnet (2 miles). For homes towards Hertfordshire, Potters Bar is around 6 miles away.
Planning rules in Friern Barnet
In England a single-storey rear extension can usually go up to 3 m beyond the original rear wall of a semi-detached or terraced house, or 4 m on a detached house, without a planning application, provided it is no more than 4 m high, keeps eaves to 3 m within 2 m of a boundary and, with other buildings, covers no more than half the land around the original house. The larger home extension prior approval scheme raises those depths to 6 m and 8 m, with neighbours notified and a 42-day decision.
In England a single-storey side return infill is often permitted development if it stays within the height limits and is no wider than half the width of the original house. Conservation areas, listed buildings and flats always need an application, and the boundary wall usually brings in the Party Wall Act.
In a conservation area, national park, National Landscape, the Broads or a World Heritage Site the permitted development limits are tighter (no side or two-storey extensions without an application). Listed homes need listed building consent, and if permitted development rights have been removed, any extension needs an application.
Building regulations approval is separate from planning. In England you can use the council's building control team or a registered building control approver; a full plans application gets the drawings checked before work starts, and the inspector signs the work off with a completion certificate.
Applications are decided by the local planning authority (your district, borough or unitary council).
Guide prices for Friern Barnet
Prices on this page use our London factor of ×1.3, include VAT at 20% and cover the build; your written price follows a survey and agreed drawings.
| Extension type | Example size | Standard spec (inc VAT) |
|---|---|---|
| Double-storey extensions | 32 m² | £74,500 – £98,000 |
| Side return extensions | 11 m² | £34,000 – £43,000 |
| Kitchen extensions | 20 m² | £54,500 – £69,000 |
| Single-storey rear extensions | 20 m² | £53,000 – £68,000 |
| Orangery extensions | 16 m² | £58,000 – £73,000 |
| Conservatory replacement extensions | 14 m² | £39,000 – £50,500 |
| Extensions over a garage | 12 m² | £32,500 – £42,500 |
What works best for Friern Barnet houses?
London's housing is dominated by Victorian and Edwardian terraces, many with a rear outrigger and a side return, and 1930s semis in the outer boroughs. Conservation areas are common, so the planning check comes first.
Depending on the plot, side return extensions and wraparound extensions are often the strongest options, with glass box extensions worth considering where there is room.
Every extension type in Friern Barnet
- Planning permission for extensions · from £450
- Annexe extensions · from £71,500
- Home office extensions · from £20,500
- Building regulations for extensions · from £1,150
- Double-storey extensions · from £49,000
- Bedroom extensions · from £33,500
- Kitchen extensions · from £35,000
- Timber frame extensions · from £27,000
- Side extensions · from £28,500
- Extensions over a garage · from £31,000
- Glass box extensions · from £39,000
- Bungalow extensions · from £34,000
- Flat roof extensions · from £27,000
- Conservatory replacement extensions · from £26,000
- Wraparound extensions · from £46,500
- Side return extensions · from £23,000
- Extension plans and drawings · from £1,550
- Orangery extensions · from £39,000
- Pitched roof extensions · from £28,500
- Porch extensions · from £5,200
- Utility and boot room extensions · from £18,000
- Single-storey rear extensions · from £27,000
Free site visit
First, a site visit: we look at the house, garden, access and drains and listen to what you need.
Design and approvals
We produce the drawings and structural design, and manage the approvals so they are in place before work starts.
Fixed written price
The price is fixed in writing once the design is settled, with a clear programme and payment stages.
Build and sign-off
Work is carried out to the agreed programme, inspected by building control and signed off at the end.
Questions about extensions in Friern Barnet
How much does an extension cost in Friern Barnet?
Using our London factor (×1.3), a standard-spec single-storey extension of 20 m² is a guide £53,000 to £68,000 including VAT, and a 32 m² two-storey extension £74,500 to £98,000. Your written price follows the survey.
Do you cover all of Friern Barnet?
Yes, including the surrounding parts of Greater London. Site visits are free and there is no obligation.
Who do I contract with?
Your contract is with S&K Property Investments and Improvement Ltd, which designs and manages the project and the build teams who carry it out.
Do you handle building regulations?
Yes. We prepare the drawings and calculations, submit them and book inspections, ending with a completion certificate.
Can I get a price before anyone visits?
Yes. This page shows guide prices adjusted for Friern Barnet, and the guide-price tool gives a range for your own size and finish in about a minute.
Book a free site visit in Friern Barnet
We will measure up, check the planning position and give you honest guide figures.
- Free, no-obligation site visit
- Planning route checked before you spend on drawings
- Written price once the design is agreed
- Building control sign-off at the end
Prefer to talk? Call 0800 088 6341 or .
Book a free site visit
Tell us a little about the project and we will arrange a time.