ProjectCalcWhat "permitted development" means
In England, most householder work does not need a planning application because the Government has already granted permission for it in the Town and Country Planning (General Permitted Development) (England) Order 2015 (the GPDO). That grant is not unlimited: each class of development comes with its own size, height, siting and materials restrictions, and step outside them and you need an application.
Two things follow from that, and they are the two things people get wrong. First, permitted development is still a grant of planning permission — you are relying on it, so the limits have to be respected exactly. Second, permitted development rights can have been removed for a particular property (see when PD is removed), in which case the limits below do not help you.
Plan-and-build rules that are easy to miss
- The 50% rule. For both outbuildings (Class E) and extensions (Class A), the total ground area covered by buildings within the curtilage — other than the original house — must not exceed 50% of the curtilage, excluding the ground area of the original house.
- Nothing in front. Under Class E, no part of the outbuilding may be forward of a wall forming the principal elevation of the original dwellinghouse.
- Heights are measured to the highest point, and eaves separately. For outbuildings the overall height limit and the eaves limit are two different numbers.
- Decking is the awkward one. See below — a raised platform is expressly excluded from the classes that would otherwise cover it.
Outbuildings, sheds, garages and summer houses — Class E
Class E covers "any building or enclosure, swimming or other pool" provided for a purpose incidental to the enjoyment of the dwellinghouse, plus containers for domestic heating fuel. Development is not permitted if any of the following applies.
| Limit | What the Order says |
|---|---|
| Ground covered | The total area of ground covered by buildings, enclosures and containers within the curtilage (other than the original dwellinghouse) must not exceed 50% of the total area of the curtilage (excluding the ground area of the original dwellinghouse) — E.1(b). |
| Position | No part may be situated on land forward of a wall forming the principal elevation of the original dwellinghouse — E.1(c). |
| Storeys | The building must not have more than a single storey — E.1(d). |
| Height — dual-pitched roof | 4 metres — E.1(e)(i). |
| Height — within 2 m of the boundary | 2.5 metres for a building, enclosure or container within 2 metres of the boundary of the curtilage — E.1(e)(ii). |
| Height — any other case | 3 metres — E.1(e)(iii). |
| Eaves | The height of the eaves of the building must not exceed 2.5 metres — E.1(f). |
| Listed buildings | Not permitted if the building, enclosure, pool or container would be situated within the curtilage of a listed building — E.1(g). |
| Raised platform | Not permitted if it would include the construction or provision of a verandah, balcony or raised platform — E.1(h). |
| Fuel containers | The capacity of a container must not exceed 3,500 litres — E.1(j). |
Two special areas change the answer further. In an area of outstanding natural beauty, the Broads, a National Park or a World Heritage Site, the total ground area covered by outbuildings sitting more than 20 metres from any wall of the dwellinghouse must not exceed 10 square metres (E.2). And on article 2(3) land, no part of the outbuilding may sit between a wall forming a side elevation of the dwellinghouse and the curtilage boundary (E.3).
Decking — why it is not simply an outbuilding
Decking is not named in the GPDO, and the two classes that most often cover garden structures both exclude a raised platform. Class E is not permitted if the development "would include the construction or provision of a verandah, balcony or raised platform" (E.1(h)), and the extension class, Class A, excludes the same thing at A.1(k)(i). A hard surface at ground level is a different matter — that is Class F, below.
So the practical question for a deck is not "how high can it be?" but "is this a raised platform?" If it is, it falls outside the permitted development grant that would otherwise apply and you should take it to your local planning authority. There is no height figure in the Order that turns a raised platform into permitted development, so we have not invented one.
Driveways, paths and other hard surfaces — Class F
Class F permits "the provision within the curtilage of a dwellinghouse of a hard surface for any purpose incidental to the enjoyment of the dwellinghouse as such", and the replacement of one. There are no height or area limits on the surface itself. Instead there is a drainage condition:
The condition applies where the hard surface would be between a wall forming the principal elevation of the dwellinghouse and a highway, and the area of ground covered by it — or the area replaced — would exceed 5 square metres. Where both are true, either the surface must be made of porous materials, or provision must be made to direct run-off water from the surface to a permeable or porous area or surface within the curtilage (Class F, condition F.2).
That is the whole of the "permeable driveway" rule as the Order writes it. It is triggered by the position and the area together: a small area, or one that is not between the front wall and the highway, is not caught by it.
Fences, walls and gates — Part 2, Class A
Gates, fences, walls and other means of enclosure are permitted development, subject to height:
| Situation | Maximum height above ground level |
|---|---|
| Adjacent to a highway used by vehicular traffic — school | 2 metres, provided that anything more than 1 metre above ground level does not obstruct the view of persons using the highway so as to be likely to cause danger — A.1(a)(i). |
| Adjacent to a highway used by vehicular traffic — any other case | 1 metre — A.1(a)(ii). |
| Any other gate, fence, wall or means of enclosure | 2 metres — A.1(b). |
| Maintained, improved or altered enclosure | Must not exceed its former height, or the height that would apply if newly built, whichever is the greater — A.1(c). |
| Listed building curtilage | Not permitted — A.1(d). |
Extensions — Part 1, Class A
Extensions are the most restricted class, and the limits depend on the type of house. The main numbers:
| Limit | What the Order says |
|---|---|
| Single-storey rear, detached house | More than 4 metres beyond the rear wall is not permitted — A.1(f)(i). |
| Single-storey rear, any other house | More than 3 metres beyond the rear wall is not permitted — A.1(f)(i). |
| Single-storey rear height | More than 4 metres is not permitted — A.1(f)(ii). |
| Larger rear extension (prior approval) | For a house not on article 2(3) land or a site of special scientific interest: more than 8 metres (detached) or 6 metres (other) is not permitted — A.1(g). Development beyond the 4 m / 3 m limits but within the 8 m / 6 m limits follows the prior approval procedure in A.4 and needs information given to the local planning authority first. |
| Two-storey rear extension | More than 3 metres beyond the rear wall is not permitted — A.1(h)(i). |
| Boundary opposite the rear wall | A two-storey enlargement must not be within 7 metres of a curtilage boundary opposite the rear wall — A.1(h)(ii). |
| Eaves within 2 m of the boundary | Eaves must not exceed 3 metres — A.1(i). |
| Side extension | Must not exceed 4 metres in height, must not have more than a single storey, and its width must not be greater than half the width of the original dwellinghouse — A.1(j). |
| Front and side-facing walls | The enlargement must not extend beyond a wall forming the principal elevation, or a side elevation that fronts a highway — A.1(e). |
| Ground covered | The 50% curtilage rule applies — A.1(b). |
Class A also imposes conditions. Exterior materials must be of a similar appearance to the existing house (A.3(a)); an upper-floor window in a side elevation must be obscure-glazed and non-opening below 1.7 metres above the floor of the room (A.3(b)); and where the enlargement has more than one storey the roof pitch must, so far as practicable, match the original (A.3(c)).
When permitted development does not apply at all
- Flats and maisonettes. The GPDO defines a "dwellinghouse" as not including a building containing one or more flats, or a flat within such a building (article 2). The Part 1 householder rights described above are rights for dwellinghouses, so they are not available to a flat in these terms.
- Conservation areas and other article 2(3) land. Article 2(3) land is the land described in Part 1 of Schedule 1 to the Order, which includes land designated as a conservation area under section 69 of the Planning (Listed Buildings and Conservation Areas) Act 1990, an area of outstanding natural beauty, and the other designations listed there. Different restrictions bite on that land — for example Class E is restricted by E.3 and a single-storey extension cannot extend beyond the rear wall at all under A.2(c).
- Listed buildings. Development is not permitted within the curtilage of a listed building (Class E.1(g); Class A of Part 2, A.1(d)). A listed building also has its own consent regime: the GPDO takes the definition of "listed building" from section 1 of the Planning (Listed Buildings and Conservation Areas) Act 1990, and works to a listed building are dealt with by the local planning authority, not by the permitted development classes.
- Article 4 directions. The Secretary of State or the local planning authority may make a direction that the permission granted by article 3 does not apply to a specified class of development, or to a particular development, in a specified area (article 4(1) of the Order). Where an article 4 direction applies, you need an application for the work it covers. Your local planning authority keeps the register of directions affecting its area, so that is the place to check for your address.
Planning permission is not the only gate
Building regulations are a separate regime from planning, and crossing one does not cross the other. Some garden buildings are exempt from building regulations altogether under Schedule 2 to the Building Regulations 2010 — for example a detached single-storey building of no more than 30 m² containing no sleeping accommodation with no point less than 1 metre from the curtilage boundary (or built substantially of non-combustible material), a detached building of no more than 15 m², and a ground-level extension consisting of a conservatory, porch, covered yard or covered way or a carport open on at least two sides of no more than 30 m². Those exemptions are about building regulations; they say nothing about planning permission.
Excavating near a neighbour — the Party Wall etc. Act 1996
There is a third regime, and it is the one most often missed on a boundary job such as fence posts, a deck, a soakaway or a footing. Section 6 of the Party Wall etc. Act 1996 applies where a building owner proposes to excavate, or excavate for and erect a building or structure:
- within a distance of three metres measured horizontally from any part of a building or structure of an adjoining owner, and any part of the proposed excavation, building or structure will within those three metres extend to a lower level than the bottom of the foundations of the adjoining owner's building or structure; or
- within a distance of six metres measured horizontally from any part of a building or structure of an adjoining owner, and any part of the proposed excavation, building or structure will within those six metres meet a plane drawn downwards at an angle of forty-five degrees to the horizontal from the line formed by the intersection of the level of the bottom of the adjoining owner's foundations with the plane of the external face of their external wall.
Where the section applies, the building owner must, at least one month before beginning to excavate, serve notice on the adjoining owner indicating the proposals and stating whether they propose to underpin or otherwise strengthen or safeguard the foundations of the adjoining owner's building or structure.
Notice under the Act is not a planning application and is not a building regulations application. It is a separate notice with its own timescales, and the one month runs from service — so it has to be thought about before the job is booked, not after the holes are marked out.
England only
The Order above applies to England. Scotland, Wales and Northern Ireland have their own planning and building regimes, and their own permitted development rules. The library hub lists what we verified for the other nations.
Last verified 22 September 2026. Every requirement quoted on this page was read from the primary source listed below on that date, not from a summary. If a figure could not be confirmed in the primary source it is not on this page.
Where these figures come from
- Town and Country Planning (General Permitted Development) (England) Order 2015, Schedule 2, Parts 1 and 2 and article 2(3) (as amended) — legislation.gov.uk, checked 22 September 2026.
- Town and Country Planning (General Permitted Development) (England) Order 2015, Schedule 2, Part 2 (gates, fences, walls) — legislation.gov.uk, checked 22 September 2026.
- Town and Country Planning (General Permitted Development) (England) Order 2015, article 2(3) and Schedule 1, Part 1 (article 2(3) land); article 4 (directions restricting permitted development) — legislation.gov.uk, checked 22 September 2026.
- Building Regulations 2010, Schedule 2 (exempt buildings and work), Classes 6 and 7 — legislation.gov.uk, checked 22 September 2026.
- Party Wall etc. Act 1996, section 6 (adjacent excavation and construction) — legislation.gov.uk, checked 22 September 2026.
Guidance only, not advice
This page is a plain-English summary of published regulations and standards, written to help you plan a job. It is not professional advice, it is not a substitute for the actual document, and it is not a building-control decision.
Building regulations are enforced by your local authority (or an approved inspector) and the facts of a particular job can change the answer. Confirm with your local building control before you start work, and where a job is structural, get it designed by a suitably qualified person. If this page and the source document disagree, the source document wins.