The standard permitted development depth limit for a rear extension is 3 metres on a semi-detached or terraced house, and 4 metres on a detached house. But there's a route that lets you go deeper - up to 6 metres on a semi or terrace, and up to 8 metres on a detached house - without a full planning application. It's called the larger home extension scheme, and it works through a process called prior approval.
Prior approval is not full planning permission. It's a lighter process with a lower fee (£249 instead of £548), a shorter timeline, and a narrower scope of assessment. But it involves consulting your immediate neighbours - and if they object, the outcome is less certain.
On a typical semi-detached house, the standard PD limit of 3 metres gives you a decent kitchen extension. But 6 metres through prior approval gives you something fundamentally different - a kitchen-dining room that opens the entire rear of the house, with space for a table, a sofa area, and still room to cook without feeling cramped. On a detached house, 8 metres creates a ground floor that can genuinely change how the house works.
The scheme was originally introduced as a temporary measure in 2013 and made permanent in May 2019. It applies to single storey rear extensions only - not side extensions, not two storey extensions, and not front extensions.
6 metres on a terrace. 8 metres on a detached house. No full planning application required.
You submit a prior approval application to your council through the Planning Portal. You include a description of the proposed extension, a plan showing its position and dimensions, and the addresses of your immediate neighbours (adjoining properties). The fee is £249.
The council then writes to your adjoining neighbours, giving them 21 days to comment. After that, the council has 42 days from the date of your application to make a decision. Three outcomes are possible.
No objections received: If no neighbour objects within 21 days, approval is either granted by the council or deemed to be granted after 42 days. This is the best-case scenario and the most common outcome on detached houses with good separation from neighbours.
Objections received: If a neighbour objects, the council must assess the impact of the extension on the amenity of adjoining properties. They consider factors like loss of light, overshadowing, and the visual impact of the extension. The council then decides whether to approve, approve with conditions, or refuse.
No decision within 42 days: If the council doesn't respond within 42 days, prior approval is deemed to be granted. You can proceed.
Want to check whether your extension qualifies for the standard PD limits first? A free eligibility check takes about two minutes.
A larger extension through prior approval must still meet all the other Class A conditions. The extension must be single storey only, with a maximum height of 4 metres. Eaves within 2 metres of a boundary are capped at 3 metres. Materials must match the existing house. It must be a rear extension only - not forward of the principal elevation and not beyond a side wall. The 50% curtilage rule applies. And depth is still measured from the original rear wall, not from any existing extension.
The prior approval route is available in conservation areas and on other designated land. However, in dense urban areas - particularly mid-terrace houses in London with neighbours on both sides and short gardens - a neighbour objection is more likely, and the council's assessment of amenity impact becomes the deciding factor.
Use prior approval when: you want a deeper single storey rear extension than the standard PD limits allow, your neighbours are likely to be supportive (or far enough away not to be affected), and the extension meets all other Class A conditions.
Use full planning permission when: you want a two storey extension, a side extension, a front extension, or anything that doesn't meet the Class A conditions. Also consider full planning permission if you know your neighbours will object strongly - at least with a full application, the council assesses a wider range of factors and you have more opportunity to present your case through a Design and Access Statement.
For the standard PD depth limits and all other Class A conditions, see our extensions guide.
Common mistakes that cost money
Starting work before the 42 days are up. You must wait for either a formal decision or the expiry of the 42-day period. Starting work before then means the extension doesn't have permission.
Assuming no objection means automatic approval. Even without objections, wait for the council's written confirmation or the 42-day deemed approval. Some councils issue formal decisions; others rely on the deemed approval mechanism.
Not realising the extension still needs to meet all other PD conditions. Prior approval only relaxes the depth limit. Every other Class A condition - height, eaves, materials, curtilage, boundary distances - still applies in full.
PD Assessment Tool
Our free eligibility check tells you whether your property qualifies for permitted development. If your extension exceeds the standard depth limits, the full assessment explains the prior approval route and checks every other condition that still applies.
Free eligibility check. Full assessment £47.
Content verified against the Town and Country Planning (General Permitted Development) (England) Order 2015 (as amended), Class A of Part 1, Schedule 2, paragraphs A.1(g) and A.4 (legislation.gov.uk, revised version). Larger home extension scheme made permanent by SI 2019/907. Fees confirmed as of 1 April 2026. This page is for general information only and does not constitute legal advice.
April 2026