Most homeowners who want a bigger kitchen or a family room at the back of the house hope they can build it without a full planning application. In England, permitted development (PD) rights let you do exactly that for many houses, but the rules are precise, and a few centimetres over a limit or one overlooked condition can turn a lawful build into an enforcement problem. This guide goes through the Class A rear-extension limits, the larger-home extension scheme that raises the depth to 6 m or 8 m, the situations in which rights do not apply, and what you still need besides planning.
The rules below apply to houses in England. Scotland, Wales and Northern Ireland have different regimes, and flats and maisonettes have no householder PD rights for extensions.
Check you actually have the rights
Permitted development rights apply to houses, not flats or maisonettes, and they can be taken away. Before measuring anything, check:
- Article 4 directions. A council can remove specific PD rights in an area, often in conservation areas or around heritage assets. Your local planning authority will tell you.
- Planning conditions. A condition attached to the original permission (common on estates built in the last few decades) may have removed PD rights for extensions.
- Listed buildings. PD rights do not extend to listed buildings; you need listed building consent as well as planning permission.
- Previous alterations. The limits are cumulative, counted against the “original house”: the house as first built, or as it stood on 1 July 1948 if it was built before then. Earlier extensions, including those by previous owners, count.
- How the house was created. Rights do not apply where the home was converted under PD from another use such as offices.
The basic limits for a single-storey rear extension
According to the Planning Portal, for a single-storey rear extension the depth beyond the rear wall of the original house is limited to:
| House type | Standard PD limit | With prior approval (neighbour consultation) |
|---|---|---|
| Detached | 4 metres | 8 metres |
| Semi-detached, terraced and other | 3 metres | 6 metres |
The larger limits do not apply on Article 2(3) land (see below) or on a Site of Special Scientific Interest. The maximum height of a single-storey rear extension is 4 metres.
Conditions that apply to every extension
- Half the land. Extensions and other buildings (sheds, garages, outbuildings) cannot cover more than half the area of land around the original house. Garden space already taken up counts.
- Height. No part of the extension can be higher than the highest part of the existing roof, and the eaves cannot be higher than the existing eaves.
- Eaves near the boundary. If any part of the extension is within 2 metres of a boundary, the eaves height cannot exceed 3 metres.
- Not forward. The extension cannot extend beyond the principal elevation, or beyond a side elevation that fronts a highway.
- Materials. Materials must be similar in appearance to the existing house. Matching brick, render or tile finish is expected.
- No raised platforms. The PD rights do not allow verandas, balconies or raised platforms, nor new chimneys, flues or soil and vent pipes on the extension.
The larger home extension scheme
To build beyond 3 m (or 4 m for detached houses), up to 6 m (or 8 m), you do not need full planning permission, but you do need to notify the council through the “prior approval” route, often called the neighbour consultation scheme. Roughly, the process goes like this:
- You submit an application to the local planning authority with a written description, plans, the address of the property and the details of the extension, including its depth, height and materials.
- The council notifies the adjoining neighbours and gives them at least 21 days to comment.
- If any adjoining neighbour objects, the council assesses the impact on neighbours’ amenity, specifically considering the effect on their enjoyment of their home. If no objection is made, the extension may proceed under the prior approval.
- The council issues a decision. You must complete the development within a stated period and notify the council on completion.
The fee is much lower than a full householder planning application. The council’s decision is made on amenity grounds: sunlight, outlook and overbearing effect on neighbours. Careful design, such as keeping height low near the boundary, usually helps. Do not start building before approval is confirmed: a council that has not responded within the statutory period may be taken to have no objection, but check the position and keep records.
Two-storey and side extensions
- Two-storey rear extensions may extend up to 3 metres beyond the rear wall, and must be at least 7 metres from the rear boundary opposite. The roof pitch must match the existing house as far as practicable, and upper-floor side windows must be obscure-glazed and non-opening unless the opening part is more than 1.7 m above the floor. On Article 2(3) land, rear extensions of more than one storey need planning permission.
- Side extensions must be single storey, no more than 4 metres high, and no wider than half the width of the original house. They always require planning permission on Article 2(3) land.
Where the rights are reduced: Article 2(3) land
Article 2(3) land includes conservation areas, National Parks, Areas of Outstanding Natural Beauty (now named National Landscapes in England), the Broads and World Heritage Sites. In these locations, side extensions need planning permission, two-storey rear extensions need permission, and the larger single-storey limits (6 m and 8 m) are not available. Cladding with stone, artificial stone, pebble dash, render, timber, plastic or tiles may also be restricted. If you live in one of these areas, call the planning department before doing anything.
Worked example
Take a 1960s semi-detached house on a plot with a rear garden 15 m deep. The original rear wall is the starting point. Suppose a previous owner added a conservatory on the back that projected 2 m (a conservatory counts as an extension). A new kitchen extension must then be assessed with it. If the conservatory is removed and replaced, only the new extension counts, which is the usual approach. If the conservatory stays and the new extension would project 3 m from the original wall in a different part of the rear wall, the combined enlargement still must comply with the half-the-land rule. The simplest method: draw the original rear wall, measure from it, and show the council each dimension. Our permitted development extension compliance audit tool helps check these dimensions against the published limits, and the Planning Portal or your council gives the final word. Half-the-land check with example numbers: if the original house has a 200 m² plot around it (garden and outbuildings), the extension plus all other buildings must stay under 100 m²; an existing 12 m² shed plus a new 25 m² extension totals 37 m², well within the limit.
Certificate of lawful development
Permitted development means you do not need to apply, but a lawful development certificate (LDC) from your council confirms in writing that the proposal is lawful. Buyers’ solicitors often ask for evidence that an extension was lawful, and an LDC saves arguments later. It costs a fraction of a full application. Without it, you rely on your own reading of the rules, with the risk of enforcement if you are wrong.
What else you still need
- Building regulations. PD removes the need for planning permission, not for building regulations. Foundations, structure, insulation, drainage, electrics, ventilation and fire safety all need approval, via building control or an approved inspector. See our guide on which projects need building regulations approval.
- Party Wall etc. Act 1996. If you build on or near the boundary, excavate close to a neighbour’s foundations or cut into a party wall, you must serve notices on the adjoining owners. This is separate from planning.
- Drains and sewers. Building over or near a public sewer may need the water company’s consent.
- Structure. Opening up the rear wall needs a structural engineer’s calculations for steel beams, and timber elements need correct sizing; see timber joist sizing and notching.
- Foundations and slabs. Use the concrete slab volume calculator for rough quantities, but foundation depth must come from building control and soil conditions.
- Community Infrastructure Levy (CIL). Some councils charge CIL on new floor area above a size threshold; many householder extensions under 100 m² are exempt. Ask your council.
- Other consents. Trees with Tree Preservation Orders, protected species such as bats, and flood-risk areas can all affect what you can do.
Policy may change
The government has consulted on widening householder PD rights, including bigger extensions, and policy continues to evolve. At the time of writing, the Planning Portal’s published limits are those described here, but always check the current position before applying or building. The technical guidance on GOV.UK states its latest edition date and the legislation it reflects.
This is general information, not legal or planning advice. If a boundary, a covenant or a previous extension is unclear, talk to your local planning authority or a planning consultant.