Rear extension drawings in Barnet from £625
Finchley, Golders Green, Hendon, Mill Hill and Barnet: how deep Barnet normally accepts, where Hampstead Garden Suburb takes the right away, and which route fits your house.
£625 £475 drawings + £150 survey (£625 total), no VAT to add
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The short answer
Barnet’s design guidance says a single-storey rear extension is normally acceptable at 3 metres deep on a terraced house, 3.5 metres on a semi-detached house and 4 metres on a detached one, and two storeys within 2 metres of the boundary should not go beyond 3 metres. In Hampstead Garden Suburb the Article 4 direction removes the enlargement right altogether. Our fee is £475 drawings + £150 survey (£625 total), no VAT to add; the council’s fee is separate.
Rear extension drawings
from £625
- Drawings
- £475
- Measured survey
- £150
- Total you pay
- £625
- VAT
- None to add
- A measured survey of the back of the house, the garden levels and the neighbours’ windows and extensions
- A check of your depth against Barnet’s norms for your house type and against the permitted development limits
- A check of your address against Barnet’s Article 4 conservation areas, including Hampstead Garden Suburb
- Existing and proposed plans, a roof plan, elevations and a section, each with a scale bar and the site address
- The certificate, prior approval notice or householder application that fits, submitted for you with free redraws
£475 drawings + £150 survey (£625 total). A starting fee: we confirm one fixed figure after checking your address. The council’s own fee, where there is one, is paid to the council.
Get my fixed feeHow a Barnet rear extension runs
Depth check
We identify your house type, any earlier extension and any Article 4 direction, then say how deep Barnet will normally accept.
Survey
We measure the back, the garden levels, the neighbours’ rear building lines and the trees within 15 metres.
Design
You choose a depth and roof in plan and 3D, knowing which route each one needs.
Draw and submit
We draw to Barnet’s list and submit by the route that fits, then answer the case officer.
How deep Barnet normally accepts
Barnet’s Residential Design Guidance gives its own depth norms for a single-storey rear extension: 3 metres for terraced properties, 3.5 metres for semi-detached and 4 metres for detached. They apply on top of the tests that matter more: no significant sense of enclosure or loss of outlook from, or light to, the principal windows of neighbouring rooms, and no bulk out of scale with the house and garden.
The norms bend with the neighbours. If the house next door sits lower or has a rear wall set back from yours, the guidance says your depth may need to be reduced; if your garden is already below the amenity standard, an application will normally be refused. For example, a semi-detached house in Finchley with a neighbour whose kitchen window sits close to the boundary may be asked for less than 3.5 metres even though the norm allows it.
Two storeys, and permitted development as the fallback
For a two-storey rear extension Barnet says one closer than 2 metres to a boundary and projecting more than 3 metres is not normally acceptable, and flat roofs on two-storey rear extensions are not normally acceptable either. On widely spaced semis and detached houses there may be more scope.
Permitted development under Class A is the benchmark for a single storey: 3 metres on a terrace or semi and 4 metres on a detached house, or 6 and 8 metres through a larger home extension notice. A deeper scheme than Barnet’s norm can therefore be lawful without a full application, which we prove with a certificate. Hampstead Garden Suburb is the exception: its Area 1 direction withdraws the right to enlarge or alter a dwelling.
What Barnet’s checklist adds, and CIL
Barnet’s householder checklist asks for a section unless the elevations barely change, a roof plan unless the roof does not change, a tree survey where a tree stands within 15 metres of the work, and a CIL additional information form. A scale bar of at least 5 or 10 metres and the site address go on every sheet, and no sheet says “do not scale”. Missing items stop an application being validated.
Barnet’s residential CIL is £300 a square metre for permissions granted from 1 April 2022, with Mayoral CIL on top, and it generally starts at 100 square metres of new floor area. A single-storey kitchen extension is normally below that; a large two-storey one may not be, so we measure the new floor area before you commit.
Rear extensions in Barnet in numbers
1081 of 1136
Householder decisions by Barnet Council between July 2025 and June 2026 (prior approvals left out) that were made inside 8 weeks.
Source: MHCLG live table PS2, district planning application statistics, July 2025 to June 2026 (GOV.UK)
3 / 3.5 / 4 m
Depth Barnet normally accepts for a single-storey rear extension: terraced, semi-detached, detached.
2 m and 3 m
A two-storey rear extension closer than 2 metres to a boundary and deeper than 3 metres is not normally acceptable.
3 m / 4 m
Deepest single-storey extension permitted development allows; 6 and 8 metres through prior approval.
Source: GPDO 2015, Schedule 2, Part 1, Class A: enlargement of a dwellinghouse (legislation.gov.uk)
10
Barnet conservation areas covered by Article 4 directions, including Hampstead Garden Suburb.
Class A
Hampstead Garden Suburb Area 1: the right to enlarge or alter a dwelling is withdrawn.
Source: Hampstead Garden Suburb conservation area Article 4 directions (Barnet Council)
15 m
Distance within which trees on the site, next door or on the street trigger a tree survey.
Source: Validation checklist: householder application (Barnet Council)
£300
Barnet CIL per square metre for residential development granted permission from 1 April 2022.
Source: Community Infrastructure Levy (CIL) (Barnet Council)
£72.73
Mayoral CIL per square metre for permissions granted in 2026 in Barnet, which is in band 2 (£60 when set in 2019). It applies only where CIL is due at all.
Source: Mayoral CIL: Annual CIL Rate Summary 2026 (London.gov.uk)
100 m²
New-build floor area below which CIL does not arise unless the work creates a dwelling.
Source: CIL Regulations 2010, regulation 42: exemption for minor development (legislation.gov.uk)
Questions about rear extensions in Barnet
Is 4 metres the most I can build at the back of a Barnet semi?
Not necessarily. The council’s norm for a semi is 3.5 metres, but permitted development allows 3 metres, and a larger home extension notice 6 metres, so the route decides how far you can go.
Can I build a two-storey rear extension in Barnet?
Usually with a full application. Barnet does not normally accept one deeper than 3 metres within 2 metres of the boundary, and avoids flat roofs on them.
Does Hampstead Garden Suburb need an application for a single-storey extension?
Yes. Its Article 4 direction removes the right to enlarge a dwelling, so permitted development does not apply.
Will I pay CIL on a kitchen extension?
Normally not. CIL generally starts at 100 square metres of new floor area, and Barnet still asks for the information form to confirm it.
See how far your Barnet house can go
Send the address and a photo of the back. We reply with the route and a fixed fee, from £475 drawings + £150 survey (£625 total).