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 Hammersmith and Fulham

House extension plans in Hammersmith and Fulham, £895 fixed

Hammersmith & Fulham's Planning Guidance SPD (28 February 2018) says permission will not normally be granted for a rear extension more than 3.5 metres long, one within 4 metres of the rear boundary, or one that, with earlier extensions, covers more than 50% of the open area at the rear of the house as originally built.

Planning drawings£895
Building regs£795
Council fee£548
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Boroughs33/33
Stages5

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 Hammersmith and Fulham Council asks of a house extension

From the council's Planning Guidance SPD (February 2018) (adopted 28 February 2018, council page).

  • Permission will not normally be granted for a rear extension more than 3.5 metres long or, where the house has already been extended, where existing and proposed extensions together would project more than 3.5 metres beyond the back addition as originally built. (source, checked 14 October 2026)
  • Nor where the extension would come within 4 metres of the rear boundary. (source, checked 14 October 2026)
  • Nor where it, together with any earlier extensions, would cover more than 50% of the open area at the rear of the house as originally built. (source, checked 14 October 2026)
  • A 45-degree line is used: measured from ground level at the rear boundary where the neighbouring garden is under 9 metres long, or from 2 metres above ground where it is longer. (source, checked 14 October 2026)
  • An extension beside the original back addition should not rise above 2 metres on the boundary, measured from the neighbour’s ground level, with a roof slope no steeper than 45 degrees. (source, checked 14 October 2026)
  • New windows should be at least 18 metres from existing habitable room windows, measured on a 60-degree arc. (source, checked 14 October 2026)

What Hammersmith and Fulham house extension drawings have to show

The Hammersmith & Fulham SPD measures cumulatively, so the drawings show the back addition as originally built, every later extension and then the proposal. Permission will not normally be granted where together they project more than 3.5 metres beyond that original back addition, come within 4 metres of the rear boundary, or cover more than 50% of the open area at the rear of the house as originally built.

The 45-degree line is then drawn on the section: from ground level at the rear boundary where the neighbouring garden is under 9 metres long, or from 2 metres above ground where it is longer. An extension beside the original back addition should not rise above 2 metres on the boundary, measured from the neighbour's ground level, with a roof slope no steeper than 45 degrees. New windows should be at least 18 metres from existing habitable room windows, measured on a 60-degree arc.

The council's validation checklist, a file dated 21 June 2017, asks for a design and access statement when a householder proposal affects a listed building or a conservation area, and a tree survey for building work within five metres of the crown spread of any tree, including street trees and trees on neighbouring land.

Hammersmith and Fulham guidance · rear depth

How deep Hammersmith and Fulham expects a single-storey rear extension to be

Any house, beyond the original rear building line3.5 mDepth beyond the original rear wall · dashed line: permitted development
Source: Planning Guidance SPD (February 2018). 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

Hammersmith and Fulham: 506 householder decisions

Hammersmith and Fulham
Approvals, prior approvals included97.8%

495 of 506 granted. London: 85.8%.

Decided within 8 weeks86.9%

152 of 175 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 Hammersmith and Fulham

  • Planning drawings: £895, plus £548 to Hammersmith and Fulham Council.
  • Building regulations drawings: £795.

House extension plans across London · Hammersmith and Fulham planning rules · every price

Answers

Hammersmith and Fulham house extension questions

How long can a rear extension be in Hammersmith and Fulham?
The SPD says permission will not normally be granted for a rear extension more than 3.5 metres long. Nor will it normally be granted where the extension would come within 4 metres of the rear boundary, or where it and any earlier extensions would cover more than 50% of the open area at the rear of the house as originally built.
How high can a side return extension be on the boundary in Hammersmith and Fulham?
The SPD says an extension beside the original back addition should not rise above 2 metres on the boundary, measured from the neighbour's ground level, with a roof slope no steeper than 45 degrees. It also uses a 45-degree line, taken from ground level at the rear boundary where the neighbouring garden is under 9 metres long, or from 2 metres above ground where it is longer.
Does an earlier extension count against the 3.5m limit?
Yes. Where the house has already been extended, the SPD says permission will not normally be granted where existing and proposed extensions together would project more than 3.5 metres beyond the back addition as originally built. The 50% open-area limit is also counted together with earlier extensions.
Does an Article 4 direction affect a rear extension in Hammersmith and Fulham?
It can. The council lists more than 40 directions in conservation areas, each covering named addresses and particular works. In Bradmore (1), for example, any structure at ground or first-floor level behind the rear wall needs permission. Check your address against the council's list before relying on permitted development.

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