Two Victorian terraced houses on a London street, one painted white and one in yellow stock brick, with bay windows
Floor plan drawings, pencil sketches of a house, a scale rule and a protractor spread across a desk
Photo: Tima Miroshnichenko / Pexels

House extension plans · London Borough of Brent

House extension plans in Brent, £895 fixed

Brent's Residential Extensions and Alterations SPD (adopted 16 January 2025) says single storey rear extensions could be up to 6 metres deep on attached homes and 8 metres on detached homes, but never more than half the garden length. It is not intended for properties in conservation areas or listed buildings.

Planning drawings£895
Building regs£795
Council fee£548
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Boroughs33/33
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Photo: Huy Phan / Pexels

The back of a house extension at shell stage, with a large glazed opening, blockwork walls and a scaffold tower
An extension at shell stage: the opening, the blockwork and the beam above it are what the building regulations drawings describe. Photo: Brett Jordan / Pexels.

What Brent Council asks of a house extension

From the council's Residential Extensions and Alterations SPD (January 2025) (adopted 16 January 2025, council page).

  • For attached homes, such as terraced or semi-detached homes, single storey rear extensions could be up to 6 metres in depth from the original rear wall; for detached homes, up to 8 metres. Notwithstanding this, the depth must not be more than half the length of the garden, and the garden retained should meet the amenity space standards in Local Plan Policy BH13. (source, checked 15 October 2026)
  • Single storey rear extensions up to 3 metres deep (attached) or 4 metres deep (detached) could be up to 4 metres high as long as the eaves are no more than 3 metres. Deeper extensions could also be up to 4 metres high as long as the eaves are no more than 2.5 metres along the boundary to any neighbouring property. (source, checked 15 October 2026)
  • Two storey rear extensions must not be more than 3 metres deep from the original rear wall on attached homes, or 4 metres on detached homes, and must not extend beyond the 45 degree line(s) measured from the middle of the nearest habitable room window(s) on the original rear wall of any neighbouring property. (source, checked 15 October 2026)
  • The height of two storey rear extensions must not be more than the roof ridgeline of the original home, with the eaves no higher than those of the original home. (source, checked 15 October 2026)
  • Extensions to outriggers could be up to the full width of the side return, must not extend more than 3 metres from the end wall of the outrigger, and must not be more than 3.5 metres high where they adjoin the outrigger, with eaves of no more than 2.5 metres along the boundary. Those that create inner rooms should incorporate a lightwell at least 2 metres deep from the rear wall. (source, checked 15 October 2026)

What Brent house extension drawings have to show

Brent's figures start from the original rear wall, so the drawings dimension the depth from that wall and show the length of the garden, because the SPD says the depth must not be more than half of it, whatever the 6 or 8 metres could allow. The garden retained should meet the amenity space standards in Local Plan Policy BH13. Heights are drawn too: for an extension up to 3 metres deep (attached) or 4 metres deep (detached) the SPD says it could be up to 4 metres high as long as the eaves are no more than 3 metres, and deeper extensions could also be up to 4 metres high as long as the eaves are no more than 2.5 metres along the boundary to any neighbouring property.

A two storey rear extension must not be more than 3 metres deep on attached homes or 4 metres on detached homes, and must not extend beyond the 45 degree line measured from the middle of the nearest habitable room window on the original rear wall of any neighbouring property. Its height must not be more than the roof ridgeline of the original home, with the eaves no higher than those of the original home. An extension to an outrigger could be up to the full width of the side return, must not extend more than 3 metres from the end wall of the outrigger and must not be more than 3.5 metres high where it adjoins it, with eaves of no more than 2.5 metres along the boundary. One that creates inner rooms should incorporate a lightwell at least 2 metres deep from the rear wall.

The council's householder checklist (checked 10 October 2026) asks for photographs of the site and its context and a landscape plan with all applications, and a heritage statement for any works covered by an Article 4 direction. The SPD says its guidance is not intended for properties in conservation areas or listed buildings; for those, the council's heritage officer advises. Brent has 22 conservation areas, and its residential conservation areas are covered by Article 4 directions that can include front windows and doors, painting the front, paving front gardens, roof tiles and chimneys (council pages, 10 October 2026). The SPD was adopted on 16 January 2025, as the council's SPD page shows, and we checked it on 15 October 2026.

Brent guidance · rear depth

How deep Brent expects a single-storey rear extension to be

Attached (terraced or semi), single storey6 mDetached, single storey8 mDepth beyond the original rear wall · dashed line: permitted development
Source: Residential Extensions and Alterations SPD (January 2025). The marker shows the national permitted development depth (GPDO 2015, Schedule 2, Part 1, Class A, A.1(f): 4 m detached, 3 m otherwise), which applies only where no application is needed.
Permitted development · Class A

How far a single-storey rear extension can go before it needs more than a drawing

Terraced or semi-detached

Existing houseNo applicationPrior approvalPlanning application3 m6 mDepth beyond the original rear wall

Detached

Existing houseNo applicationPrior approvalPlanning application4 m8 mDepth beyond the original rear wall

Height, side view

HouseBoundary2 m4 m maxoverall height3 m eaveswithin 2 m of boundary
Source: GPDO 2015, Schedule 2, Part 1, Class A: A.1(f) (3 m, or 4 m if detached; 4 m high), A.1(g) (6 m, or 8 m if detached; not on article 2(3) land such as conservation areas, nor on a site of special scientific interest), A.1(i) (eaves over 3 m within 2 m of a boundary) and the prior approval procedure in A.4. Terraced and semi-detached houses are the “any other dwellinghouse” case. Other conditions still apply: check the permission section and run the checker.
PS2 · at a glance

Brent: 879 householder decisions

Brent
Approvals, prior approvals included86.6%

761 of 879 granted. London: 85.8%.

Decided within 8 weeks97.4%

643 of 660 applications, prior approvals excluded.

Source: MHCLG PS2, 1 July 2025 to 30 June 2026. Dark tick: London.
A bright kitchen with white cabinets, a stainless steel range cooker and extractor hood, and a window over the sink
A kitchen in a rear extension: the wide opening into it from the old house is carried by a beam. Photo: Curtis Adams / Pexels.

What it costs in Brent

  • Planning drawings: £895, plus £548 to Brent Council.
  • Building regulations drawings: £795.

House extension plans across London · Brent planning rules · every price

Answers

Brent house extension questions

How deep can a single-storey rear extension be in Brent?
The SPD says single storey rear extensions could be up to 6 metres deep from the original rear wall on attached homes, such as terraced or semi-detached homes, and up to 8 metres on detached homes. "Could" is the SPD's word. In every case the depth must not be more than half the length of the garden, and the garden retained should meet Policy BH13. The SPD is not intended for conservation areas or listed buildings.
How high can an extension be on the boundary in Brent?
For extensions up to 3 metres deep (attached) or 4 metres deep (detached), the SPD says they could be up to 4 metres high as long as the eaves are no more than 3 metres. Deeper extensions could also be up to 4 metres high as long as the eaves are no more than 2.5 metres along the boundary to any neighbouring property.
Can I extend into the side return of an outrigger in Brent?
The SPD says extensions to outriggers could be up to the full width of the side return, but must not extend more than 3 metres from the end wall of the outrigger and must not be more than 3.5 metres high where they adjoin it, with eaves of no more than 2.5 metres along the boundary. Those that create inner rooms should incorporate a lightwell at least 2 metres deep from the rear wall.

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