Under Schedule 2, Part 1, Class A of the General Permitted Development Order 2015, a single-storey rear extension can reach 6m on most houses and 8m on a detached house, once the council's prior approval process has run. The process lasts up to 42 days. Conservation areas, National Parks and other article 2(3) land are excluded.
The route is often called the larger home extension scheme. Ordinary permitted development stops at 3m, or 4m on a detached house. This scheme doubles those depths in return for a notification to the council, a notice to your neighbours and a fee. The council does not grant planning permission. It decides whether its prior approval is needed, and that turns on whether an adjoining neighbour objects.
Key Takeaways
- The depth limits are 8m for a detached house and 6m for any other house, with a maximum height of 4m (paragraph A.1(g) of Class A).
- The scheme is closed to article 2(3) land, which includes conservation areas, and to sites of special scientific interest.
- The council must tell adjoining owners and occupiers, who get at least 21 days to respond. You cannot start until the council decides or 42 days pass.
- The council fee is £249 for applications made on or after 1 April 2026. It is indexed each April.
- Earlier extensions count: depth is judged on the total enlargement beyond the original rear wall.
How deep can a larger home extension be?
A single-storey rear extension can project up to 8m beyond the original rear wall of a detached house and 6m beyond any other house, with a maximum height of 4m. Without prior approval the limits are 4m and 3m. The greater depth is unavailable on article 2(3) land or a site of special scientific interest.
| Extension | No prior approval (A.1(f)) | With prior approval (A.1(g)) |
|---|---|---|
| Single storey, detached house | 4m | 8m |
| Single storey, any other house | 3m | 6m |
| Height of single-storey extension | 4m | 4m |
| More than one storey | 3m, and not within 7m of the boundary opposite the rear wall (A.1(h)) | Not available |
"Any other house" includes semi-detached, end-of-terrace and terraced houses. Two further limits catch people out. Where the extension comes within 2m of a boundary, its eaves may not exceed 3m (A.1(i)). And all buildings other than the original house may not cover more than 50% of the curtilage, not counting the original house's footprint (A.1(b)).
The measurement runs from the rear wall of the "original" house. Article 2 of the Order defines original as the building as it stood on 1 July 1948, or as first built if it is newer.
Which houses and sites cannot use the scheme?
The scheme is closed to houses on article 2(3) land and sites of special scientific interest, to flats, and to houses whose residential use exists only through certain Part 3 change-of-use rights. Local article 4 directions and planning conditions can also remove it, so check both before drawing anything.
Article 2(3) land is defined in Schedule 1, Part 1 of the Order. It covers conservation areas, areas of outstanding natural beauty, areas specified under section 41(3) of the Wildlife and Countryside Act 1981, the Broads, National Parks and World Heritage Sites. On that land you can still build the ordinary 3m or 4m single-storey rear extension, but paragraph A.2 adds restrictions of its own: no side extensions, no extension of more than one storey beyond the rear wall, and no cladding in stone, render, pebble dash, timber, plastic or tiles.
Also excluded are:
- houses whose use as a dwellinghouse was granted only through Part 3 Classes G, M, MA, N, P, PA or Q (A.1(a)), and houses built under Part 20 (A.1(l));
- buildings containing flats, because Article 2 says a dwellinghouse does not include them;
- land covered by an article 4 direction, which lets a council withdraw Class A in an area or for a particular development;
- a house covered by a planning condition, since Article 3(4) says the Order permits nothing contrary to one;
- a house whose own construction was unlawful (Article 3(5)).
Our London borough pages name the article 4 areas for each borough covered, and the permitted development checker will say plainly if you need no application at all.
What does the council fee cost?
The council fee for a larger home extension prior approval is £249 for applications made on or after 1 April 2026, set by regulation 14(1)(zab) of the Fees Regulations 2012 and indexed. It was £240 from 1 April 2025. It is paid to the council, separately from any fee of ours.
Regulation 14(1)(zab) fixes the base amount and regulation 18A raises fees each 1 April by the September rise in the Consumer Prices Index, capped at 10%. The 2026 amount comes from the government's fees table for 1 April 2026, which lists the figure for a larger rear extension under Part 1 Class A. Because it moves every April, confirm it on the day you submit. Regulation 14 refunds it if the application is rejected as invalid.
What must you send the council?
Before building, you must send the council a written description of the extension, a plan showing the site and the development, the addresses of adjoining premises, your contact address and the fee. The description gives the depth beyond the rear wall, the maximum height and the eaves height (paragraph A.4(2)).
Your email address is included if you are content to receive messages electronically. The council may refuse an application that does not comply, or where the information is too thin to judge (A.4(3)). It may also ask for more information it reasonably requires (A.4(8)).
How does the neighbour consultation work?
The council must serve a notice on each adjoining owner or occupier. It describes the extension, gives the property address, states the date by which the 42 days would expire and sets a deadline for representations of not less than 21 days from the date of the notice. Public holidays are disregarded when counting those days (A.4(5) and A.4(16)).
If an adjoining owner or occupier objects, the council's prior approval is required, and the only question is the impact on the amenity of adjoining premises (A.4(7)). The council must weigh the representations it receives and the amenity of all adjoining premises, not only those of people who wrote in (A.4(9)). It may grant approval unconditionally or with conditions reasonably related to that impact (A.4(12)). If nobody objects, the council still decides whether the extension complies, but no amenity assessment is triggered.
How long is the 42-day period?
Building must not begin until one of three things happens: the council gives written notice that prior approval is not required, the council gives written notice granting it, or 42 days pass from the day it received your information without the council saying whether approval is given or refused (A.4(10)).
The clock runs from receipt, so a complete first submission matters. Once you start, you must build in line with the approved details or, if none were needed, the information you supplied, unless the council agrees a change in writing (A.4(11)). A refusal for non-compliance or missing information skips the neighbour notice and is treated as a refusal for appeal purposes under section 78 (A.4(3) and A.4(4)).
How do earlier extensions count towards the limit?
Depth is judged on the total enlargement: the new part together with any existing enlargement of the original house that it joins (A.1(ja)). A 3m extension built by a previous owner plus a new 3m extension attached to it is a 6m enlargement, so it needs this route and cannot go past 6m on a semi-detached house.
Your written description must give the depth, height and eaves of that total enlargement, not only of the new part (A.4(2)(a)(iv)). Check old drawings and the borough's planning history before measuring.
How does this show up on drawings and fees?
Prior approval deals with planning only. Building regulations are a separate approval, so an extension that gets prior approval still needs construction drawings. Those are £795 from Fixed Fee Plans, fixed, and the council's building control charge is set separately.
If your scheme goes beyond 6m or 8m, or sits on article 2(3) land, a householder application is the route. Our complete planning drawing service is £895, and the council's householder fee is £548, paid to the council. Our house extensions page walks through the sequence. A shared wall may also need notices, covered in our Party Wall Act guide. Beams and openings need an engineer, and our calculations service is from £495; see Part A and calculations and Part L for extensions.
What else do people ask about larger extensions?
Most questions concern who qualifies and when work may start. Only single-storey rear extensions qualify, only outside article 2(3) land and sites of special scientific interest, and work may start only when the council writes to you or the 42 days expire.
Can I build 8m on a semi-detached house?
No. The 8m depth applies only to a detached house. Every other house stops at 6m under paragraph A.1(g).
Can I start early if my neighbours agree?
No. The ban on starting in paragraph A.4(10) applies whatever neighbours think.
Where do these figures come from?
Every figure comes from legislation.gov.uk or a gov.uk document, fetched on 10 October 2026. The Order, the Fees Regulations and the government's fee table supply the limits, periods and fees, and the technical guidance explains them. The links show where each one sits.
- General Permitted Development Order 2015, Schedule 2, Part 1, Class A, paragraphs A.1 to A.4 (6m and 8m, 4m height, 21 days, 42 days): https://www.legislation.gov.uk/uksi/2015/596/schedule/2/part/1
- The Order, Article 2 (original, dwellinghouse): https://www.legislation.gov.uk/uksi/2015/596/article/2
- The Order, Article 3 (conditions, unlawful buildings): https://www.legislation.gov.uk/uksi/2015/596/article/3
- The Order, Article 4 (directions): https://www.legislation.gov.uk/uksi/2015/596/article/4
- The Order, Schedule 1, Part 1 (article 2(3) land): https://www.legislation.gov.uk/uksi/2015/596/schedule/1
- Fees Regulations 2012, regulation 14(1)(zab) (£240 from 1 April 2025): https://www.legislation.gov.uk/uksi/2012/2920/regulation/14
- Fees Regulations 2012, regulation 18A (indexation): https://www.legislation.gov.uk/uksi/2012/2920/regulation/18A
- Planning fees from 1 April 2026 (£249, Part 1 Class A prior approval): https://assets.publishing.service.gov.uk/media/69a073bb07d7bff3604d6df6/Planning_fees_-_annual_indexation_from_1_April_2026.pdf
- Permitted development rights for householders: technical guidance, 2019 (neighbour consultation scheme): https://assets.publishing.service.gov.uk/media/5d77afc8e5274a27cdb2c9e9/190910_Tech_Guide_for_publishing.pdf