Barnet, London
House extension drawings in Barnet
House extension drawings in Barnet start at £695 including VAT. Barnet's guidance sets the depth of a single-storey rear extension by house type, at 3 m terraced; 3.5 m semi-detached; 4 m detached, and the Planning Inspectorate has allowed 50.6 per cent of the householder appeals it decided here, so we draw to the guidance from the start rather than relying on an appeal.
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House extension drawings in Barnet: depth, height and the boundary
The rules sit in the Sustainable Design and Development Guidance SPD, Part 4: Guidance on residential extensions and alterations, which supports the Barnet Local Plan 2021-2036. A single-storey rear extension should be no deeper than 3 m terraced; 3.5 m semi-detached; 4 m detached, measured from the original rear wall. The detached figure is the most generous, and the terraced figure the tightest.
Depth is not the only test. The extension should not be more than half the garden length, and it must leave the outdoor amenity space the local plan requires. Height is limited to 4 m max height; 3 m eaves. We therefore draw the garden as a measured plan with the retained space marked, not as an afterthought.
Other shapes have their own figures. A side-return extension can fill the whole passage but should be no higher than 2 m on the boundary on the neighbouring boundary. A wraparound extension should normally keep to 3 m depth; 2 m on the boundary, the depth measured beyond the two-storey rear wall of the outrigger, and a two-storey rear extension is held to 3 m depth; 1 m / 2 m from boundary.
Local figures for Barnet
| Measure | Value | Period | Source |
|---|---|---|---|
| Single-storey rear extensions should be no deeper than 3 metres for terraced, 3.5 metres for semi-detached and 4 metres for detached houses, measured from the original rear wall. | 3 m terraced; 3.5 m semi-detached; 4 m detached | — | barnet.gov.uk, SDDG SPD Part 4 (extensions), p.7, paras 4.37-4.39 |
| A single-storey rear extension should not be more than half the length of the garden and must leave the Local Plan Table 10 outdoor amenity space. | half the garden length | — | barnet.gov.uk, SDDG SPD Part 4 (extensions), p.7, para 4.40 |
| Single-storey rear extensions can be up to 4 metres high if the eaves are no more than 3 metres. | 4 m max height; 3 m eaves | — | barnet.gov.uk, SDDG SPD Part 4 (extensions), p.7, paras 4.41-4.42 |
| Side-return (outrigger) extensions can fill the full width and length of the side return but should be no higher than 2 metres on the neighbouring boundary, measured from the applicant's side. | 2 m on the boundary | — | barnet.gov.uk, SDDG SPD Part 4 (extensions), p.14, paras 4.46-4.49 |
| Two-storey side extensions should be no more than half the width of the house, keep a 1 metre gap to the boundary at first floor, be set back at least 0.5 metre from the front wall and set down 0.5 metres from the ridge. | 1 m gap; 0.5 m set-back; 0.5 m set-down | — | barnet.gov.uk, SDDG SPD Part 4 (extensions), p.19, paras 4.69-4.74 |
| Householder appeals decided by the Planning Inspectorate | 413 householder appeals decided | decision dates 1 Jul 2021 to 30 Jun 2026 | assets.publishing.service.gov.uk |
| Householder appeals allowed | 50.6 % of householder appeals allowed | decision dates 1 Jul 2021 to 30 Jun 2026 | assets.publishing.service.gov.uk |
| Conservation areas | 16 named conservation areas published by the council | — | planning.data.gov.uk |
| Article 4 directions | 15 Article 4 directions published by the council | — | planning.data.gov.uk |
| Green Belt share of the council area | 28 % of council area covered by green-belt polygons | — | planning.data.gov.uk |
| Householder decisions | 1,361 decisions | 1 July 2025 - 30 June 2026 | assets.publishing.service.gov.uk |
| Householder applications granted | 80.2 % | 1 July 2025 - 30 June 2026 | assets.publishing.service.gov.uk |
| Householder: alterations/extensions to a single dwellinghouse, from 1 Apr 2026 | 548 GBP | — | ribblevalley.gov.uk |
A blank value means the figure has not been published, not that there are none. Check your own address with the council.
Householder applications by street in Barnet
| Street | Applications | Approved |
|---|---|---|
| Wolmer Gardens | 42 | 82% |
| Hampden Way | 36 | 86% |
| Oakleigh Park South | 36 | 77% |
| Marsh Lane | 35 | 91% |
| Millway | 34 | 93% |
| Sturgess Avenue | 34 | 94% |
| Uphill Road | 32 | 73% |
| Chanctonbury Way | 31 | 90% |
| Oakleigh Road North | 30 | 79% |
| Woodlands | 30 | 76% |
| Laurel Way | 29 | 76% |
| Mount Pleasant | 28 | 80% |
| Arlington Road | 27 | 80% |
| Berkeley Crescent | 27 | 100% |
| Longland Drive | 27 | 100% |
Single-storey rear extension: the permitted development limits
The house in section with a rear extension; the dashed lines mark the zone near the boundary.
- A · Depth beyond the original rear wall
- 3 m (attached) / 4 m (detached) beyond the original rear wall, single storey
- B · Maximum height
- 4 m
- C · Within the zone near the boundary
- Eaves no higher than 3 m where within 2 m of the curtilage boundary
- D · Larger extension under prior approval
- 6 m (attached) / 8 m (detached), single storey, height max 4 m; not on article 2(3) land or an SSSI
Two-storey side extensions
For a two-storey side extension the guide asks for 1 m gap; 0.5 m set-back; 0.5 m set-down, the gap kept at first floor, and no more than half the width of the house. Those gaps keep a pair of houses reading as a pair, and a terrace reading as a terrace, so we draw the front elevation first and test the set-back against the neighbour before anything else is designed.
Where the side gap is the question, a side return extension in Barnet is a different animal from a two-storey one, and the page on double-storey extension drawings in Barnet deals with that route.
What Barnet's appeal record means for your drawings
The Planning Inspectorate decided 413 householder appeals in Barnet in the five years to its latest published date, and allowed 50.6 per cent. That is roughly half of the appeals decided, and each was judged on its own facts and evidence.
On the council's own record, it decided 1,361 householder applications in the latest year, granted 80.2 per cent and decided 95.1 per cent in time. We treat these as background for the timetable, not as a forecast. What we can control is the drawing: complete dimensions, a labelled garden plan and a street elevation that shows the proposal against the houses either side.
Green Belt, conservation areas and Article 4
About 28 per cent of the borough is Green Belt, which changes how the size of an extension is judged. Barnet also has 16 conservation areas and 15 Article 4 directions, mapped as 48 separate areas, and Historic England lists 651 entries.
Each of those can remove permitted development, so we check the address before we recommend a route. If you may have the right, our rear extension drawings in Barnet page explains the steps. If you do not, the application goes through the same drawings with a fuller design statement, and we prepare that with the set so it is ready when the council asks.
Cost, fees and what you receive
Our fee starts at £695 with VAT included and is fixed before you commit, and drawings are normally ready about a week after the survey. The set comprises existing and proposed plans, elevations and sections, a location plan and a block plan. The council's householder fee is £548, paid to the council.
A second chartered technologist checks every sheet before it is submitted, and we redraw at no charge until approval if the council asks for changes. Energy rules apply to the new walls, roof and floor, and the limits are: New elements in existing dwellings, limiting U-values W/(m²·K): roof 0.15, wall 0.18, floor 0.18, windows 1.4 (or WER Band B), doors 1.4.
Nearby boroughs and the wider service
The overall picture for the borough is at architectural drawings in Barnet, and the national rules are on the house extension drawings hub. We never reuse a design from one road on another: each set starts from a fresh survey of your house and the houses either side. Next door, compare Harrow and Brent and their local guidance.
What you receive
Related pages
Other services in Barnet
Questions
How deep can a single-storey rear extension be in Barnet?
Barnet's guidance says 3 m terraced; 3.5 m semi-detached; 4 m detached, measured from the original rear wall. It also limits the extension to half the garden length.
How much do house extension drawings cost in Barnet?
From £695 including VAT, fixed before you commit. The council fee for a householder application is paid separately.
Can I extend a two-storey house to the side in Barnet?
Yes, within limits. The guide asks for 1 m gap; 0.5 m set-back; 0.5 m set-down, and no more than half the width of the house.
What if Barnet refuses my application?
You can appeal within the statutory period. The Planning Inspectorate allowed 50.6 per cent of the householder appeals it decided in the period shown, though each case is judged on its own facts.
Sources and dates
- barnet.gov.uk, retrieved
- assets.publishing.service.gov.uk, retrieved
- planning.data.gov.uk, retrieved
- planning.data.gov.uk, retrieved
- planning.data.gov.uk, retrieved
- assets.publishing.service.gov.uk, retrieved
- ribblevalley.gov.uk, retrieved
- barnet.gov.uk, retrieved
- barnet.gov.uk, retrieved
- planning.data.gov.uk, retrieved
- planning.data.gov.uk, retrieved
- gov.uk, retrieved
- legislation.gov.uk, retrieved
- Contains public sector information licensed under the Open Government Licence v3.0.
- Contains OS data © Crown copyright and database right 2026.
- Contains HM Land Registry data © Crown copyright and database right 2026. This data is licensed under the Open Government Licence v3.0.
- Contains Historic England data © Historic England 2026. Contains Ordnance Survey data © Crown copyright and database right 2026.
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