Rear extension drawings in Hillingdon from £625
Uxbridge, Ruislip, Hayes and Northwood: Hillingdon took away the right to build single-storey extensions deeper than 4 metres without permission.
£625 £475 drawings + £150 survey (£625 total), no VAT to add
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The short answer
Hillingdon removed permitted development rights for single-storey rear extensions over 4 metres deep, with an Article 4 direction due to take effect on 22 September 2014. So the 6 and 8 metre larger home extension route is not available there; anything over 4 metres needs a planning application. The council’s HDAS guidance, as it applies it, accepts up to 3.6 metres, 3 metres high with a flat roof. 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 plot and the neighbours’ extensions
- A depth check against the 4 metre line and against the 3.6 metre figure the council quotes from HDAS
- A check of your address against Hillingdon’s 31 conservation areas
- Existing and proposed plans and elevations to the February 2024 validation checklist, with a 1:500 block plan
- The route that fits submitted for you, and answers to the case officer
£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 Hillingdon rear extension runs
Depth check
We compare your wish list with the 3.6 and 4 metre lines and the neighbours’ extensions.
Survey
We measure the back, the garden and the neighbours’ windows and extensions.
Design
You choose a depth and roof, with the route and the risk of each written down.
Draw and submit
We prepare the pack to the checklist and submit it, then answer the case officer.
The 4 metre Article 4 direction
In 2013 the government raised the permitted depth for single-storey extensions to 6 metres, or 8 on a detached house, through a neighbour consultation. Hillingdon’s officers reported in 2014 that deeper extensions can harm both the character of the borough and residential amenity, and asked the council to confirm an Article 4 direction withdrawing permitted development rights for single-storey rear extensions of over 4 metres depth, due to come into force on 22 September 2014.
In practice that means the standard 3 or 4 metres still needs no application on a house outside a conservation area, but a 5 metre kitchen is a planning application. That is a different cost and timeline from the prior approval route used in neighbouring boroughs, and we say so at the start.
What the council accepts when you apply
The council’s committee report of 20 March 2018 quotes its Residential Extensions SPD, adopted in December 2008. Section 3.0 says single-storey rear extensions up to 3.6 metres deep will be acceptable and up to 3 metres high with a flat roof; paragraph 6.0 says up to 3.6 metres deep on semi-detached houses where they appear subordinate and do not cause significant overshadowing, loss of outlook or daylight. Two-storey extensions must meet the 45 degree line of sight.
The same report shows the figure is not a wall: officers accepted a 5.1 metre single-storey extension, 3 metres high with a flat roof, while noting it exceeded 3.6 metres. For example, a deep kitchen is a better case where it is low, flat and the neighbour has a similar depth.
Validation, conservation areas and CIL
Hillingdon has 31 conservation areas, and a heritage statement is needed on a householder application in one. Its February 2024 checklist asks for an existing and proposed block plan at 1:500 and floor plans and elevations at 1:50 or 1:100.
Hillingdon CIL for residential permissions granted in 2026 is £160.43 a square metre, on 100 square metres or more of new floor space, so a typical extension is outside it. Mayoral CIL is in band 2.
Rear extensions in Hillingdon in numbers
637 of 678
Householder decisions by Hillingdon 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)
4 m
Depth beyond which Hillingdon’s Article 4 direction removes permitted development for a single storey rear extension.
22 Sep 2014
Date Hillingdon’s rear-extension Article 4 direction was due to come into force.
3.6 m
Depth of single-storey rear extension the council’s report says its HDAS guidance accepts, with 3 metres height under a flat roof.
5.1 m
Depth of a single-storey rear extension officers accepted in 2018 although it exceeded the 3.6 metre figure.
45°
Line of sight a two-storey extension must satisfy under the HDAS guidance quoted in the report.
31
Designated conservation areas in Hillingdon, from village centres to planned residential estates.
1:500
Scale of the existing and proposed block plan Hillingdon asks for with a householder application.
Source: Local Planning Validation Checklist, February 2024 (Hillingdon Council)
£160.43
Hillingdon CIL per square metre for residential permissions granted in 2026, from a £95 rate indexed by 400/237.
£72.73
Mayoral CIL per square metre for permissions granted in 2026 in Hillingdon, 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)
Questions about rear extensions in Hillingdon
Can I use the 6 metre larger home extension route in Hillingdon?
No. Hillingdon’s Article 4 direction removes permitted development for single-storey rear extensions over 4 metres, so those need a planning application.
How deep will the council accept?
Its guidance accepts up to 3.6 metres. Officers have accepted more, such as 5.1 metres, where the design and neighbours allowed it.
Do I need a heritage statement?
Yes on a householder application in a conservation area or for a listed or locally listed building.
Do I pay CIL on a kitchen extension?
Not normally. CIL arises at 100 square metres of new floor space or where a dwelling is created.
See how far your Hillingdon 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).