Outbuilding Size Checker: Does Your Garden Room or Shed Need Planning Permission?

The Class E rules, one by one

• Class E is the permitted development right for buildings in the garden of a house. It covers any building, enclosure or pool "required for a purpose incidental to the enjoyment of the dwellinghouse as such", and tanks storing oil or LPG for heating the house. (legislation.gov.uk, as at 26 Sep 2026)

• The government's examples include garden sheds, other storage buildings, garages and garden decking up to 0.3 metres high, as long as they can properly be described as incidental to the enjoyment of the house. A building attached to the house isn't covered by Class E: it counts as an extension under Class A, so use the extension size checker instead. (MHCLG, 10 Sep 2019)

• Class E sets no fixed floor-area limit. Size is controlled by the height limits, the single-storey rule, the 50% rule and, in some protected landscapes, a 10 m² cap on buildings more than 20 metres from the house. (legislation.gov.uk, as at 26 Sep 2026)

• No part of it can sit forward of a wall forming the principal elevation of the original house (paragraph E.1(c)), and it can only have a single storey (E.1(d)). (legislation.gov.uk, as at 26 Sep 2026)

• The principal elevation is usually the part of the house that faces the main road serving it, and a house has only one. On a corner plot, a view has to be taken on which side it is. The front-garden rule also covers anywhere in front of a line drawn from the principal elevation out to the side boundary. (MHCLG, 10 Sep 2019)

• Height limits (E.1(e)): 4 metres for a building with a dual-pitched roof, 2.5 metres for a building, enclosure or container within 2 metres of the boundary of the garden, and 3 metres in any other case. The eaves can't be higher than 2.5 metres (E.1(f)). (legislation.gov.uk, as at 26 Sep 2026)

• Buildings, enclosures and containers other than the original house can't cover more than 50% of the curtilage, leaving out the ground the original house stands on (E.1(b)). There is a worked example further down this page. (legislation.gov.uk, as at 26 Sep 2026)

• Class E doesn't allow a veranda, balcony or raised platform (E.1(h)). In the householder rules, "raised" means a platform with a height greater than 0.3 metres. (legislation.gov.uk, as at 26 Sep 2026)

• A heating oil or LPG tank can hold no more than 3,500 litres (E.1(j)). Nothing that relates to a dwelling or to a microwave antenna, such as a satellite dish, is covered (E.1(i)). (legislation.gov.uk, as at 26 Sep 2026)

• Class E was last changed on 1 August 2021, and legislation.gov.uk lists no changes to it waiting to be applied. (legislation.gov.uk, as at 26 Sep 2026)

• A government consultation in February 2024 asked about changing Class E, including allowing bin and bike stores in front gardens and removing the 10 m² cap in protected landscapes. No outcome had been published and the law hadn't changed by 26 September 2026, so the checker uses the rules in force. (MHCLG, 13 Feb 2024)

How to measure height, eaves and the 2 metre zone

• Heights are measured from ground level, which the Order defines as the surface of the ground immediately next to the building. Where the ground isn't level, it is the highest part of the ground next to it. (legislation.gov.uk, as at 26 Sep 2026)

• Ground level doesn't include anything laid on top of the ground, such as decking. Measure from the ground itself, not from a deck or raised base the building stands on. (MHCLG, 10 Sep 2019)

• Height is measured to the building's highest point. If any part of the building is within 2 metres of the boundary, the 2.5 metre limit applies to the whole building. The 4 metre limit for dual-pitched roofs also applies to hipped roofs, which slope on all four sides. (MHCLG, 10 Sep 2019)

• The checker takes the boundary distance from the nearest part of the building, counting any roof overhang or gutter, and treats exactly 2 metres as within 2 metres. That is the cautious reading. If you want the higher limit, keep every part more than 2 metres from the boundary.

• The eaves are "the point where the lowest point of a roof slope, or a flat roof, meets the outside wall of the building". They can be no higher than 2.5 metres on any part of the building, whatever its overall height. (MHCLG, 10 Sep 2019)

• Parapet walls and overhanging eaves are left out when measuring eaves height. So on a flat-roofed garden room the roof can be no higher than 2.5 metres where it meets the wall. A parapet can rise above that, but it counts towards the overall height limit. (MHCLG, 10 Sep 2019)

• A figure exactly at a limit passes, because the Order only rules out a height that "would exceed" it. Uneven ground and building tolerances can add a few centimetres, so the checker warns you when a height or eaves figure is less than 10 cm under its limit. (legislation.gov.uk, as at 26 Sep 2026)

Working out the 50% rule

• Paragraph E.1(b) compares two figures: the ground covered by buildings, enclosures and containers other than the original house, and the area of the curtilage minus the ground area of the original house. The first can't be more than 50% of the second. (legislation.gov.uk, as at 26 Sep 2026)

• Every extension counts, whether it was built under permitted development or with planning permission, and so does every outbuilding, existing or proposed. That includes detached buildings from before 1948 and, for a newer house, a garage built at the same time as the house. (MHCLG, 10 Sep 2019)

• "Original" means the house as it stood on 1 July 1948, or as it was built if it was built after that date. Anything added later, such as an extension, conservatory or porch, counts towards the 50%. (legislation.gov.uk, as at 26 Sep 2026)

• The curtilage is land that "forms part and parcel with the house". It is usually the garden and the land the house sits on, but for a house with large grounds it may be a smaller area, so the council may not count all the land you own. (MHCLG, 10 Sep 2019)

• Worked example: a house stands on a 200 m² plot and the original house covers 80 m², so the rule measures against 200 minus 80, which is 120 m². Half of that is 60 m². A rear extension covers 30 m² and an old shed and greenhouse cover 20 m². A new 4 m by 3 m garden room adds 12 m², making 62 m², or 51.7%, which is over the limit. Taking down 4 m² of the old buildings as part of the project brings the total to 58 m², or 48.3%, which is within it.

• Measured against the whole 200 m² plot, the same 62 m² would look like 31%. That is why the checker asks for the original house's footprint separately.

• Paragraph E.1(b) counts "buildings, enclosures and containers" and, unlike other Class E limits, doesn't mention pools. If a new pool would only take you over 50% when it is counted, the checker asks you to confirm with the council how it treats pools. (legislation.gov.uk, as at 26 Sep 2026)

Conservation areas, National Parks and other protected land

• "Article 2(3) land" means conservation areas, Areas of Outstanding Natural Beauty (now also called National Landscapes), areas specified under section 41(3) of the Wildlife and Countryside Act 1981, the Broads, National Parks and World Heritage Sites. (legislation.gov.uk, as at 26 Sep 2026)

• On all article 2(3) land, including conservation areas, no part of an outbuilding, enclosure, pool or tank can go between a wall forming a side elevation of the house and the boundary of the garden (paragraph E.3). Behind the house is still possible if the other limits are met. (legislation.gov.uk, as at 26 Sep 2026)

• In an Area of Outstanding Natural Beauty, the Broads, a National Park or a World Heritage Site, buildings, enclosures, pools and containers more than 20 metres from any wall of the house can cover no more than 10 m² in total (paragraph E.2). Conservation areas aren't on that list, so the 10 m² cap doesn't apply in a conservation area. (legislation.gov.uk, as at 26 Sep 2026)

• Natural England refers to "AONBs, or national landscapes". A proposed new AONB or boundary extension, such as the Surrey Hills extension it submitted in September 2026, gains no new status unless and until the Secretary of State confirms it. (Natural England, 10 Sep 2026)

• Green belt and flood zones aren't article 2(3) land, so they don't reduce Class E rights. They matter if you need to apply for planning permission. (legislation.gov.uk, as at 26 Sep 2026)

• If you don't know whether your home is on protected land, the checker runs these two rules as if it were. If your design passes anyway, the answer makes no difference. If it doesn't, the result tells you what to check, and the conservation area checker shows what the published planning data holds for your postcode's centre point.

What you can use it for: incidental use, not living space

• Government guidance says an incidental purpose doesn't cover "normal residential uses, such as separate self-contained accommodation or the use of an outbuilding for primary living accommodation such as a bedroom, bathroom, or kitchen". (MHCLG, 10 Sep 2019)

• Working from home doesn't normally need planning permission if the work stays incidental to living there. More traffic, visitors, deliveries, noise or smells can point to a material change of use, which the council judges as "a matter of fact and degree". (MHCLG, 26 Jul 2023)

• Keeping poultry, bees, pets, birds or other livestock for your household's own needs or enjoyment counts as incidental (paragraph E.4), so a hen house or dog kennel can come under Class E. (legislation.gov.uk, as at 26 Sep 2026)

• How the checker treats use: a home office, gym, hobby room, playroom, greenhouse or store passes. A bedroom, self-contained living space, separate home or holiday let gives "needs planning permission". A kitchen, shower or toilet gives "needs checking", because whether the building stays incidental then depends on how it is used, so ask the council or apply for a lawful development certificate.

When the rights don't apply or have been removed

• Class E only applies to houses. In the Order, "dwellinghouse" doesn't include a building containing one or more flats, or a flat within one, so a flat or maisonette needs planning permission for a garden building. (legislation.gov.uk, as at 26 Sep 2026)

• Nothing within the curtilage of a listed building is permitted under Class E (paragraph E.1(g)). If your home is listed, or another listed building or structure is on the property, ask the council's conservation officer. (legislation.gov.uk, as at 26 Sep 2026)

• A home created by a permitted development change of use under Class G, M, MA, N, P, PA or Q of Part 3 has no Class E rights (paragraph E.1(a)). Nor does a home built under the Part 20 rights for new homes (E.1(k), in force since 1 August 2020). Classes MA and G were added to the list in 2021. (legislation.gov.uk, as at 26 Sep 2026)

• In plain terms, those classes cover homes converted from shops and other commercial, business and service premises, storage or distribution buildings, light industrial premises, agricultural buildings and some other uses. Part 20 covers new homes added to existing buildings, for example by building extra storeys on top. Class O, the older right to convert offices to homes, isn't on the E.1(a) list, but Class MA, which also covers offices, is. If your home used to be an office, check which right was used. (legislation.gov.uk, as at 26 Sep 2026)

• The government's 2019 technical guidance predates these changes. It still lists only Classes M, N, P, PA and Q and doesn't mention Part 20 homes, so the checker follows the current legislation instead. (MHCLG, 10 Sep 2019)

• Your council can remove permitted development rights "either by means of a condition on a planning permission, or by means of an article 4 direction". What is removed depends on the wording of each condition or direction, so read it. (MHCLG, 6 Mar 2014)

• An Article 4 direction can cover a whole Part, Class or paragraph of the rules, in a defined area or for one particular development. The conservation area checker shows Article 4 areas at your postcode where the council has published them to the national planning data service, and tells you when it hasn't. (legislation.gov.uk, as at 26 Sep 2026)

• Nothing in the Order permits development contrary to a condition on a planning permission (article 3(4)). To check, look up your address on the council's planning register and read the conditions on the permission that built the house and on any later ones. (legislation.gov.uk, as at 26 Sep 2026)

• If you're altering an existing outbuilding, permitted development doesn't apply where the building's construction was unlawful (article 3(5)(a)). (legislation.gov.uk, as at 26 Sep 2026)

• Permitted development also doesn't cover anything that obstructs the view of people using a road used by vehicles "so as to be likely to cause danger to such persons" (article 3(6)). This matters near junctions and driveways. (legislation.gov.uk, as at 26 Sep 2026)

Building regulations and other consents are separate

• Permitted development doesn't remove the need for building regulations approval or Party Wall Act consent where they apply. (MHCLG, 10 Sep 2019)

• A detached building with a floor area of no more than 15 m² and no sleeping accommodation is exempt from building regulations. (legislation.gov.uk, as at 26 Sep 2026)

• A detached single-storey building of up to 30 m² with no sleeping accommodation is exempt if no point of it is less than 1 metre from the boundary, or if it is built substantially of non-combustible material. This is where the "1 metre rule" comes from: it is a building regulations test, not a planning one. Above 30 m², or with sleeping accommodation, this exemption doesn't apply. (legislation.gov.uk, as at 26 Sep 2026)

• Covenants in your deeds are a separate legal matter. Government guidance says land ownership, including any restrictions attached to the land, "is not a planning matter". (MHCLG, 6 Mar 2014)

If a rule fails, or you want certainty

• If the result is "needs planning permission", you can change the design and check again, for example by keeping every part more than 2 metres from the boundary or lowering the eaves, or you can apply to your council.

• In England, the planning application fee for putting up a building in the garden of a house, for purposes connected with enjoying it, has been £272 since 1 April 2026. (Planning Portal, 1 Apr 2026)

• If the result is "likely permitted development" or "needs checking", a lawful development certificate is the formal way to confirm it. Government guidance says that where it isn't clear whether works are covered by permitted development rights, you can apply for one "for a legally binding decision from the local planning authority". (MHCLG, 6 Mar 2014)

• Once a certificate for proposed work is granted, the work's lawfulness is "conclusively presumed" unless something material changes before it starts. (legislation.gov.uk, as at 26 Sep 2026)

• A certificate for proposed work costs half the full planning application fee, which makes it £136 for an outbuilding at the fee in force from 1 April 2026. (Planning Portal, 1 Apr 2026)

• If you expect to need permission, a Planning Confidence Report shows how your council has decided applications like yours, and why the refused ones were refused, before you pay for drawings.

Common questions

How big can an outbuilding be without planning permission?

Class E sets no fixed floor-area limit. The limits are height (2.5 metres within 2 metres of the boundary, otherwise 3 metres, or 4 metres with a dual-pitched or hipped roof), eaves no higher than 2.5 metres, a single storey, and the 50% rule: extensions and outbuildings together can cover no more than half the curtilage, not counting the original house. In National Parks, National Landscapes, the Broads and World Heritage Sites, buildings more than 20 metres from the house are limited to 10 m² in total.

How close to my boundary can I build a garden room?

Class E sets no minimum distance, but if any part of the building is within 2 metres of the boundary, the whole building can be no more than 2.5 metres high. Building regulations are separate: a detached single-storey building of more than 15 m² and up to 30 m², with no sleeping accommodation, is exempt from them if it is at least 1 metre from the boundary or built substantially of non-combustible material.

How tall can a shed be without planning permission?

2.5 metres if any part of it is within 2 metres of the boundary. Further away, 3 metres, or 4 metres with a dual-pitched or hipped roof. The eaves can't be higher than 2.5 metres in any case. Measure from the highest ground next to the shed, not from its base or any decking.

Can I use a garden room as a bedroom?

Not under permitted development. Class E covers buildings used for something incidental to the house, such as a home office or a store. Government guidance says that doesn't include "primary living accommodation such as a bedroom, bathroom, or kitchen" or anything self-contained, so a bedroom needs planning permission. A building with sleeping accommodation also loses the building regulations exemption for small detached buildings.

Do I need planning permission for a garden room in a conservation area?

Not always. Class E still applies, but no part of the building can go between a side wall of the house and the boundary. The 10 m² cap on buildings more than 20 metres from the house doesn't apply in conservation areas, only in National Parks, National Landscapes, the Broads and World Heritage Sites. Any outbuilding in the grounds of a listed building needs permission, and your council may have removed the rights with an Article 4 direction, so check that too.

Does a garden room need building regulations approval?

Not if it is a detached building of 15 m² or less with no sleeping accommodation. A detached single-storey building of up to 30 m², still with no sleeping accommodation, is exempt if it is at least 1 metre from the boundary or built substantially of non-combustible material. Above 30 m², the small detached building exemption doesn't apply, so check with building control.

Should I get a lawful development certificate for my outbuilding?

You don't have to. It is the formal way to have the council confirm the building is lawful, and once it is granted, the lawfulness of the work is conclusively presumed unless something material changes before you start. A certificate for proposed work costs half the planning application fee, which is £136 for an outbuilding at the fee in force from 1 April 2026. Our lawful development certificate guide explains how to apply.

Does the 50% rule include my house?

No. The original house, as built or as it stood on 1 July 1948, is left out of both sides of the sum. Everything else counts: extensions, conservatories, porches, existing sheds and garages, including detached buildings from before 1948. Their total can't be more than half of the curtilage once the original house's footprint is taken away.

Sources