How far can an extension go without planning permission?
A single-storey rear extension can go 3 m beyond the original rear wall of a semi-detached or terraced house, or 4 m if it's detached, and up to 6 m or 8 m with prior approval from the council. Check yours, including side and two-storey extensions.
1. Your address (optional)
Conservation areas and other protected land rule out side and two-storey extensions and the prior approval route.Your postcode stays in your browser. We only fetch the data for its first half (for example "SW1A"). See the map and everything published for this postcode
2. Your extension
This is an example design: change the figures to yours.
Likely permitted development, with things to check
Everything we can measure fits. Read the 3 points marked Check below before you build.
This is guidance, not legal advice. For certainty, apply to your council for a Lawful Development Certificate.
Rule by rule
- FitsNot forward of the front, or of a side wall facing a roadAn extension at the back is allowed, within the limits below.Source:
Schedule 2, Part 1, Class A, paragraph A.1(e)
“the enlarged part of the dwellinghouse would extend beyond a wall which— (i) forms the principal elevation of the original dwellinghouse; or (ii) fronts a highway and forms a side elevation of the original dwellinghouse”
- CheckMeasured from the original houseThe limits are measured from the original house, as it was on 1 July 1948 or as first built, so extensions added since count towards them. Check the planning history if you're not sure.Source:
Schedule 2, Part 1, Class A, paragraph A.1(f)(i)
subject to paragraph (g), the enlarged part of the dwellinghouse would have a single storey and— “extend beyond the rear wall of the original dwellinghouse by more than 4 metres in the case of a detached dwellinghouse, or 3 metres in the case of any other dwellinghouse”
- FitsDepth beyond the original rear wall: max 3 m (semi-detached or terraced)Yours: 3 m. Limit: 3 m.Source:
Schedule 2, Part 1, Class A, paragraph A.1(f)(i)
subject to paragraph (g), the enlarged part of the dwellinghouse would have a single storey and— “extend beyond the rear wall of the original dwellinghouse by more than 4 metres in the case of a detached dwellinghouse, or 3 metres in the case of any other dwellinghouse”
- FitsHeight of a single-storey extension: max 4 mYours: 3.5 m. Limit: 4 m.Source:
Schedule 2, Part 1, Class A, paragraph A.1(f)(ii)
“the enlarged part of the dwellinghouse would have a single storey and— (i) extend beyond the rear wall of the original dwellinghouse by more than 4 metres in the case of a detached dwellinghouse, or 3 metres in the case of any other dwellinghouse, or (ii) exceed 4 metres in height”
- FitsNo higher than the highest part of the roofYours: 3.5 m. The house's roof: 8.5 m.Source:
Schedule 2, Part 1, Class A, paragraph A.1(c)
“the height of the part of the dwellinghouse enlarged, improved or altered would exceed the height of the highest part of the roof of the existing dwellinghouse”
- FitsEaves no higher than the house's eavesYours: 2.6 m. The house's eaves: 5 m.Source:
Schedule 2, Part 1, Class A, paragraph A.1(d)
“the height of the eaves of the part of the dwellinghouse enlarged, improved or altered would exceed the height of the eaves of the existing dwellinghouse”
- FitsEaves within 2 m of a boundary: max 3 mYours: 2.6 m. Limit: 3 m.Source:
Schedule 2, Part 1, Class A, paragraph A.1(i)
“the enlarged part of the dwellinghouse would be within 2 metres of the boundary of the curtilage of the dwellinghouse, and the height of the eaves of the enlarged part would exceed 3 metres”
- FitsCovers no more than 50% of the gardenYours: 8%. Limit: 50%.Source:
Schedule 2, Part 1, Class A, paragraph A.1(b)
“as a result of the works, the total area of ground covered by buildings within the curtilage of the dwellinghouse (other than the original dwellinghouse) would exceed 50% of the total area of the curtilage (excluding the ground area of the original dwellinghouse)”
- FitsJudged together with any extension it joinsIt doesn't join an earlier extension.Source:
Schedule 2, Part 1, Class A, paragraph A.1(ja)
“any total enlargement (being the enlarged part together with any existing enlargement of the original dwellinghouse to which it will be joined) exceeds or would exceed the limits set out in sub-paragraphs (e) to (j)”
- FitsMaterials look similar to the houseThey must look similar, not be identical. That's a visual judgement for the council.Source:
Schedule 2, Part 1, Class A, paragraph A.3(a)
“the materials used in any exterior work (other than materials used in the construction of a conservatory) must be of a similar appearance to those used in the construction of the exterior of the existing dwellinghouse”
- FitsProtected land: no cladding of the houseNo stone, artificial stone, pebble dash, render, timber, plastic or tiles cladding the outside of the house.Source:
Schedule 2, Part 1, Class A, paragraph A.2(a)
“it would consist of or include the cladding of any part of the exterior of the dwellinghouse with stone, artificial stone, pebble dash, render, timber, plastic or tiles”
- FitsNo balcony, veranda or raised platformNone planned.Source:
Schedule 2, Part 1, Class A, paragraph A.1(k)(i)
“the construction or provision of a verandah, balcony or raised platform”
- FitsThe house wasn't created under permitted developmentYou said it wasn't converted or built under permitted development.Source:,
Schedule 2, Part 1, Class A, paragraph A.1(a)
“permission to use the dwellinghouse as a dwellinghouse has been granted only by virtue of Class G, M, MA, N, P , PA or Q of Part 3 of this Schedule (changes of use)”
Schedule 2, Part 1, Class A, paragraph A.1(l)
“the dwellinghouse is built under Part 20 of this Schedule (construction of new dwellinghouses)”
- CheckNo Article 4 direction removes these rightsEnter your postcode above and we'll check what your council has published.Source:
Article 4(1)
“may make a direction under this paragraph that the permission granted by article 3 does not apply to— (a) all or any development of the Part, Class or paragraph in question in an area specified in the direction; or (b) any particular development, falling within that Part, Class or paragraph, which is specified in the direction”
- CheckNo planning condition removes these rightsWas your house built in the last 30 years, or on an estate? A planning condition may have removed these rights. Check the council's planning register.Source:
Article 3(4)
“Nothing in this Order permits development contrary to any condition imposed by any planning permission granted or deemed to be granted under Part 3 or Part 13 of the Act otherwise than by this Order”
3. Check for planning conditions
Was your house built in the last 30 years, or on an estate? Planning conditions may have removed these rights. When a council grants planning permission for new houses, it can attach a condition that removes some or all permitted development rights, for example extensions, outbuildings or fences. This is common on newer estates. If there is such a condition, the rights in this checker do not apply and you need planning permission. Open data does not record these conditions, so this tool cannot check them for you. The 30 years is a prompt, not a legal cut-off. A condition on a permission of any age still applies.
How to check
- Find your council's online planning register (search for the council name and "planning applications search").
- Search by your address, your road name or the estate name for the permission that allowed the house to be built. On an estate this is usually the developer's application, which may list many plots.
- Open the decision notice and read the conditions. Look for any condition that mentions the General Permitted Development Order, "permitted development", or Part 1 (Class A: extensions) of Schedule 2, or that says no extensions may be put up without permission. A condition that only removes other rights (for example outbuildings or fences) doesn't affect this project.
- Also check any later permission for your house, such as an earlier extension. Its conditions can remove rights too.
- If the permission is old and not online, ask the council's planning department, or look at the local authority search in your purchase documents.
- If you are still unsure, ask the council or apply for a Lawful Development Certificate.
Extension questions
How big can an extension be without planning permission?
A single-storey rear extension can go 3 m beyond the original rear wall of a semi-detached or terraced house, or 4 m on a detached house, and be up to 4 m high.
Under the larger home extension route you can go up to 6 m (semi-detached or terraced) or 8 m (detached), but only after telling the council and getting prior approval. That route isn't available in conservation areas, National Parks and other protected land.
What is the larger home extension (prior approval) route?
It lets a single-storey rear extension go further than the ordinary limits, up to 6 m or 8 m, if you notify the council first and it gives prior approval (or doesn't reply in time).
The council tells your adjoining neighbours, and if one objects it decides whether the effect on them is acceptable. It isn't planning permission, and the other limits still apply.
Can I build a two-storey extension without planning permission?
Sometimes, at the back: it can go up to 3 m beyond the original rear wall and must be at least 7 m from the boundary behind.
Upper-floor side windows must be obscure-glazed and high-opening, the roof pitch must match the house as far as practicable, and it isn't allowed on protected land.
How wide can a side extension be?
No wider than half the width of the original house, single storey and no more than 4 m high. Side extensions aren't permitted development in conservation areas, National Parks, the Broads, National Landscapes or World Heritage Sites.
What does "original house" mean?
The house as it stood on 1 July 1948, or as it was first built if that was later. Extensions added since, even ones a previous owner built, count towards the limits, so measure from the original rear wall.
How close to the boundary can an extension be?
As close as you like under planning rules, but if any part is within 2 m of a boundary its eaves can be no higher than 3 m. Building near a boundary may also need a party wall agreement, which is separate from planning.
The law behind these limits
- The Town and Country Planning (General Permitted Development) (England) Order 2015, Schedule 2, Part 1, Class A (enlargement, improvement or other alteration of a dwellinghouse), including the prior approval procedure in paragraph A.4, on legislation.gov.uk. Text in force from 27 August 2026, checked 14 October 2026.
- Permitted development rights for householders: technical guidance (September 2019), used only to explain words such as "original", "rear wall" and "similar appearance".
Other checks
- Check my addressSee whether protected land or an Article 4 direction changes these rules for your postcode.
- Fence, wall and gate height checkerHow high a fence, wall or gate can be: next to a road or not, on a slope, with trellis on top.
- Garden room and outbuilding checkerHeight near the boundary, roof shape, eaves, how much of the garden it covers, and use.
- Heat pump checkerAir, ground and water source, including the May 2025 changes.
- Loft and dormer checkerThe volume allowance, front roof slopes, side windows and set-backs.