Rear extension drawings in Hammersmith and Fulham from £625
Fulham, Hammersmith, Shepherd’s Bush and Parsons Green: Key Principle HS4 caps the combined length at 3.5 metres from the back addition as originally built.
£625 £475 drawings + £150 survey (£625 total), no VAT to add
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The short answer
Hammersmith and Fulham’s Planning Guidance SPD, Key Principle HS4, says permission will not normally be granted if a rear extension is more than 3.5 metres long, counting existing extensions from the back addition as originally built, comes within 4 metres of the rear boundary, or covers more than 50% of the original open area at the back. 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 that finds the back addition as originally built and every extension since
- The three HS4 tests: 3.5 metres combined, 4 metres from the rear boundary, 50% of the original open area
- The 45 degree infringing-angle test from the boundary, at ground level or 2 metres, and the 15% outlook test
- A check of your address against the borough’s conservation areas and Article 4 directions
- Plans to the council’s checklist, and the route that fits submitted for you
£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 Hammersmith and Fulham rear extension runs
Original back addition
We work out where the back addition stood as built, because HS4 measures from there.
Survey
We measure the back, the garden length and the neighbours’ windows.
Design
You choose length and roof, with the three HS4 tests and the route written down.
Draw and submit
We prepare the pack to the checklist and submit it, then answer the case officer.
The three tests in HS4
Key Principle HS4 starts with the neighbours’ established rear building lines, then sets three limits. Permission will not normally be granted if the extension is more than 3.5 metres long or, where the house has already been extended, if the existing and proposed lengths combined project more than 3.5 metres beyond the rear building line of the back addition as originally built. It will not normally be granted if the extension comes within 4 metres of the rear boundary, or if it covers more than 50% of the open area at the rear as originally built, counting existing extensions.
For example, a Fulham terrace with a 2 metre kitchen added in the 1980s has 1.5 metres left, not 3.5. The 4 metre rule matters on short gardens: a 9 metre garden cannot take more than 5 metres of extension and the 50% rule may stop it earlier.
Angles, outlook and the side of the back addition
HS6 applies a 45 degree infringing angle: measured at ground level at the boundary where the neighbouring garden is under 9 metres long, or at 2 metres above ground where it is longer. HS7 says a rear extension should not worsen outlook from a rear habitable window below it, and must not reduce the angle of unobstructed view to a back-addition window by more than 15%. An extension at the side of the back addition must not exceed 2 metres on the boundary, and its roof slope must not exceed 45 degrees. New windows should be 18 metres from existing habitable windows or designed to avoid loss of privacy.
Under Class A permitted development gives 3 or 4 metres, or 6 and 8 with prior approval, outside conservation areas. The council says about half the borough is conservation area, 44 of them, and Article 4 directions apply property by property, so we check your address first.
Validation and CIL
The council’s householder checklist asks for plans at 1:50 or 1:100, existing and proposed roof plans, a metric scale bar on every drawing, and a design and access statement from 100 square metres or in a conservation area.
CIL is payable from 100 square metres of new floor space unless a new dwelling is created, and under £50 is treated as zero, so a typical extension is outside it. Mayoral CIL is in band 1.
Rear extensions in Hammersmith and Fulham in numbers
152 of 175
Householder decisions by the London Borough of Hammersmith and Fulham 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)
3.5 m
Length beyond the back addition as originally built that existing and proposed rear extensions should not exceed together.
4 m
Distance an extension should stay from the rear boundary of the property.
50%
Share of the original open area at the rear that extensions should not cover.
45°
Infringing angle used to judge scale and massing, from ground level or 2 metres depending on garden length.
2 m
Height limit on the boundary for an extension at the side of the back addition, with a roof slope of no more than 45 degrees.
1:50 or 1:100
Scale of elevations, floor plans, roof plans and site sections in the council’s householder checklist.
44
Conservation areas, covering about half the borough, with two more in the Old Oak and Park Royal area.
Source: Conservation areas (London Borough of Hammersmith and Fulham)
By property
Where an Article 4 direction applies, planning permission is required for the restricted classes of work.
Source: Properties affected by Article 4 Directions (London Borough of Hammersmith and Fulham)
100 m²
New floor space from which CIL is payable, unless the development creates a new dwelling; under £50 is treated as zero.
Source: Community Infrastructure Levy (London Borough of Hammersmith and Fulham)
Questions about rear extensions in Hammersmith and Fulham
How long can a rear extension be?
Not normally more than 3.5 metres beyond the back addition as originally built, counting any existing extension. Permitted development with prior approval can allow more outside conservation areas.
What if my garden is short?
HS4 keeps extensions at least 4 metres from the rear boundary and under 50% of the original open area, so short gardens limit the length.
What is the 15% outlook rule?
Where there is a back addition, the angle of unobstructed view to its ground-floor window should not be reduced by more than 15%.
Do I pay CIL on a kitchen extension?
Not normally. CIL arises from 100 square metres of new floor space or a new dwelling.
See how far your Hammersmith and Fulham 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).