Prior approval for a larger rear extension in Hounslow: start with the conservation areas
Whether you can use the 6 metre or 8 metre scheme in Hounslow often comes down to one question: is the house in one of the borough's 43 conservation areas? If it is not, 270 larger home extension notifications were answered with prior approval not required in the eight quarters to June 2026, against 53 granted and 118 refused. We check the address, survey the house and draw the notification for a fixed £595.
Fixed fee from £395 drawings + £200 survey (£595 total) · all prices
Prefer to talk it through?
Forty-three conservation areas
Under Class A.1(g) of the General Permitted Development Order, a single-storey rear extension can reach 6 metres beyond the original rear wall of a terraced or semi-detached house, or 8 metres on a detached house, at no more than 4 metres high. Those larger depths do not apply in a conservation area.
Hounslow has 43 live conservation area entries on the government's planning data register at our extraction on 19 October 2026. That is a real share of the borough, so we make the check the first step, not the last. If your house is in one, we say so on the survey day and move to a householder planning application using the same survey, before you pay for notification drawings that cannot be used.
Prior Approval Extension Drawings in Hounslow
from £595
£395 drawings + £200 survey (£595 total)
Every price is the full fixed fee you pay. No VAT is charged. Council application fees are paid to the council separately.
What you get
- A conservation area check on your address before drawings are paid for
- A measured survey visit to the house and garden
- Plans and rear elevation showing depth and height at the boundary
- The written description and the list of adjoining addresses
- Submission to Hounslow as your agent, with replies to its questions
- A householder planning application route if the scheme is closed to you
- Conservation area check
The deeper extension is not allowed in a conservation area. We read the map for your address.
- Survey the house
We measure the rear wall, garden and the neighbours' windows nearest the boundary.
- Draw the notification
Plans, rear elevation, written description and adjoining addresses.
- Neighbours' 21 days
Adjoining owners and occupiers have at least 21 days to comment.
- Decision by day 42
Not required, granted or refused. Silence for 42 days lets work start.
Article 4 in Hounslow: not the extension kind
The same register lists 3 Article 4 direction areas in Hounslow, counting every class of right. Those directions cover other classes of permitted development, not extensions under Class A, so they do not stop the larger home extension scheme. A planning condition on an old permission could still remove your rights, which we look for when we read the property history.
The same register lists 3 Article 4 direction areas in Hounslow, counting every class of right.
What Hounslow has done with notifications
MHCLG publishes each council's prior approval figures every quarter. For 2024 Q3 to 2026 Q2, Hounslow's counts for larger home extensions are 270 where prior approval was not required, 53 granted and 118 refused. That is 441 in all, our sum of the three published counts.
The 270 are go-aheads, about 61% of the total on our calculation. Of the 171 that needed a decision, 118 were refused, about 69%, and 53 were granted. For a homeowner outside a conservation area, the likeliest result has been a straight pass. Where the council has had to decide, refusal has been more common than approval, and the issue is the effect on a neighbour's light or outlook.
Drawing a semi on a Hounslow street
A deep rear extension on a semi-detached house sits against the adjoining home's garden, and that neighbour is the one the council hears from. We draw the extension with the depth along that boundary and the wall height beside it marked on the plan and the rear elevation, so the council and the neighbour can read them without asking.
If the house has already been extended, the earlier work counts against the original rear wall, and the written description has to give the combined depth. We take that from the survey. Our guide to the larger home extension scheme sets out the rules in more depth.
Fee, timescales and the next step
Our fee is a fixed £595 with the survey included and no VAT charged. The council's own fee of £249 is separate. Neighbours get at least 21 days to comment, and Hounslow has 42 days from a complete notification to decide. After the decision, building regulations approval is still needed, and our building regulations drawings can use the same survey.
Sources
Every figure on this page, where it comes from and a link to the original.
| Figure | Source | Link |
|---|---|---|
| 6 metres | GPDO 2015 Sch 2 Pt 1 Class A.1(g): larger single-storey rear extension, maximum depth beyond the rear wall for a house other than detached, subject to prior approval under A.4 (source wording: "6 metres") | www.legislation.gov.uk |
| 8 metres | GPDO 2015 Sch 2 Pt 1 Class A.1(g): larger single-storey rear extension, maximum depth beyond the rear wall for a detached house (source wording: "8 metres") | www.legislation.gov.uk |
| 4 metres | GPDO 2015 Sch 2 Pt 1 Class A.1(f)-(g): a single-storey rear extension may not exceed 4 metres in height (source wording: "exceed 4 metres in height") | www.legislation.gov.uk |
| 42 days | GPDO 2015 Sch 2 Pt 1 Class A.4(10)(c): work may start if the council has not notified a decision within 42 days of receiving the information (source wording: "the expiry of 42 days") | www.legislation.gov.uk |
| £249 | Statutory fee from 1 April 2026: prior approval for a householder larger rear extension (GPDO Part 1 Class A) | assets.publishing.service.gov.uk |
| 270 | Our analysis of MHCLG planning application statistics, table PS1 (district open data table) (released 24 Sep 2026, quarters to 2026 Q2) | www.gov.uk |
| 53 | Our analysis of MHCLG planning application statistics, table PS1 (district open data table) (released 24 Sep 2026, quarters to 2026 Q2) | www.gov.uk |
| 118 | Our analysis of MHCLG planning application statistics, table PS1 (district open data table) (released 24 Sep 2026, quarters to 2026 Q2) | www.gov.uk |
| 43 | Our analysis of the MHCLG Planning Data Platform conservation-area register (extracted 19 Oct 2026) | www.planning.data.gov.uk |
| 3 | Our analysis of the MHCLG Planning Data Platform article-4-direction-area register (extracted 19 Oct 2026) | www.planning.data.gov.uk |
Questions people ask
Do Hounslow's Article 4 directions stop a larger extension?
Is my Hounslow house in a conservation area?
How often does Hounslow need no decision?
What if I am in a conservation area?
Photographs: David Howard (CC BY-SA 2.0); Derek Harper (CC BY-SA 2.0).
