Annexe extensions across Finchley
Thinking about an annexe extension for your Finchley home? Start with a free site visit: we measure up, check what the council will allow and give you honest guide figures on the day.
- Guide price in FinchleyFrom £71,500 inc VAT
- PlanningUsually a householder application
- Build time16–24 weeks on site
- Postcode districtsN2, N3, N12, NW4, NW7
Will the council need to approve it?
In England an annexe that stays part of the household and connects to the house is assessed as an extension, but its size usually takes it beyond permitted development, so a householder application describing the ancillary use is the normal route.
Before any drawing is finalised we check whether the house is listed, in a conservation area or subject to an Article 4 direction.
If the work involves a shared wall, building on the boundary, or digging foundations within 3 m (sometimes 6 m) of a neighbour's building, the Party Wall etc. Act 1996 applies and notice must be served before work starts: two months for work to a party wall, one month for new walls on the boundary and for excavations.
Applications are decided by the local planning authority (your district, borough or unitary council).
Local to Finchley
We cover Finchley and the postcode districts N2, N3, N12, NW4, NW7, NW11. Neighbouring towns we cover include Golders Green (2 miles), Friern Barnet (2 miles), Muswell Hill (2 miles), Cricklewood (3 miles).
In London, space is at a premium and gardens are often short, so side returns, wraparounds and carefully planned rear extensions tend to make the most of every metre.
Included in a typical project
- Design for accessibility: level thresholds, wider doors, walk-in shower
- Separate or shared heating and hot water
- Fire separation and alarms to building regulations
- Planning application describing ancillary use
Accessibility is cheaper to design in than to retrofit. Level access, a 900 mm door width, a level-access shower and space to turn a wheelchair can all be planned into the footprint for little extra cost.
What should I budget for an annexe extension in Finchley?
Labour and material costs vary across the UK, so for Finchley we use our London factor (×1.3). The ranges include VAT and exclude design, structural and council fees.
Typical rates in Finchley: £2,600 to £4,940 per m² including VAT, depending on specification.
| Size | Essential | Standard | Premium |
|---|---|---|---|
| Studio annexe 25 m² | £71,500 – £89,500 | £78,000 – £97,500 | £97,500 – £123,500 |
| One-bedroom annexe 35 m² | £91,000 – £114,000 | £109,000 – £136,500 | £136,500 – £173,000 |
| Larger annexe 45 m² | £117,000 – £146,500 | £140,000 – £175,500 | £175,500 – £222,500 |
For a figure based on your own dimensions, use our guide-price tool.
From first visit to completion
Site visits are free and there is no obligation. Where drawings are needed, the design stage is priced in writing before it starts.
Free site visit
We visit your Finchley home, measure up, talk through what you want and check the planning position.
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
With the design and specification agreed, you get a fixed written price and a start date.
Build and sign-off
The build is managed from start to finish, inspected at each stage and signed off on completion.
Annexe extension questions answered
Do I need building regulations approval in Finchley?
Yes. Almost every extension needs it, whatever the planning route. We prepare the drawings and book the inspections.
Who do I contract with for an annexe extension in Finchley?
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.
Will my neighbours in Finchley be involved?
If a planning application or prior approval is needed, the council notifies neighbours. If the work is on or near a shared boundary, party wall notices may also be needed.
Will an annexe affect council tax?
It can. Some annexes are assessed separately for council tax, with discounts or exemptions in some cases when occupied by a relative. Check with the Valuation Office Agency (England and Wales), your local assessor (Scotland) or Land & Property Services (Northern Ireland).
How much does an annexe extension cost?
Our guide range is about £2,600 to £4,940 per m² including VAT. A one-bedroom annexe of about 35 m² is typically £109,000 to £136,500 at standard spec in Finchley.
Book a free site visit in Finchley
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.