Permitted development rights cover most small-to-medium extensions
Permitted development (PD) is a national grant of planning permission that allows you to build certain types of extension without submitting a full planning application to your local council. It is not automatic, and you must meet specific conditions.
Most small-to-medium extensions do not need planning permission if they meet permitted development rules. For single-storey rear extensions, the limit is 6m (detached) or 4m (semi/terraced), temporarily increased to 8m and 6m until May 2027. Check conditions before building.
- Single-storey rear extensions up to 6m (detached) or 4m (semi/terraced) under PD.
- Temporary 2024 rule extends rear limits to 8m (detached) and 6m (semi/terraced) until May 2027.
- Side extensions must be single-storey, max 3m eaves, and no wider than half house width.
- PD does not apply to flats, listed buildings, or conservation areas.
- Apply for full planning permission if extension exceeds PD limits or is forward of front wall.
- Permitted development rights cover most small-to-medium extensions
- The 2024 temporary rule change extended rear extension limits until May 2027
- When you must apply for planning permission regardless of size
- Quick numbers — size limits that decide PD vs planning permission
- The direct answer to "Do you need planning permission for extension UK?"
- How to confirm your extension is permitted development using MCS, Building Regulations, and the Lawful Development Certificate
For a single-storey rear extension, the standard PD limits are 6 metres depth for a detached house and 4 metres for a semi-detached or terraced house, measured from the original rear wall of the house. Side extensions are more restricted: they must be single-storey, no wider than half the original house width, and have a maximum eaves height of 3 metres. Two-storey rear extensions must stay within 7 metres of the rear boundary and cannot be closer than 3 metres to the boundary at the rear.
PD does not apply to flats, maisonettes, listed buildings, or properties in conservation areas, Areas of Outstanding Natural Beauty, or National Parks. You cannot use PD for any extension that is forward of the principal elevation (the front wall of your house) or that is higher than the existing roof ridge line (GOV.UK, 2026).
The 2024 temporary rule change extended rear extension limits until May 2027
From 2024, the government introduced a temporary increase to permitted rear extension depths. For detached houses, the limit rose from 6 metres to 8 metres. For semi-detached and terraced houses, it rose from 4 metres to 6 metres. This change applies only to single-storey rear extensions and is set to expire on 30 May 2027 unless the government renews it (DESNZ / Ministry of Housing, 2024).
The temporary measure does not relax any other PD conditions. Your extension must still have a maximum eaves height of 3 metres, a roof pitch matching the main house, and no verandas or balconies. The extension must also be built in materials that match the appearance of the existing house.
When you must apply for planning permission regardless of size
You must submit a full planning application if your extension exceeds the PD size limits, is forward of the principal elevation, or is higher than the existing roof ridge line. Two-storey rear extensions that are more than 3 metres from the rear boundary, or within 7 metres of the boundary, trigger a neighbour consultation scheme that may block PD. Extensions that convert a house into a separate self-contained unit, such as a granny annexe with its own kitchen, are not PD and always need planning permission (GOV.UK, 2026).
If your property is listed or in a conservation area, you cannot rely on PD at all. For listed buildings, you will also need listed building consent for any external alterations. For conservation areas, you may need planning permission for even small rear extensions.
Quick numbers — size limits that decide PD vs planning permission
| Extension type | House type | Standard PD limit (metres) | Temporary PD limit (metres, until May 2027) | Height limit (metres) | Width limit (metres) | Neighbour consultation applies |
|---|---|---|---|---|---|---|
| Single-storey rear | Detached | 6 | 8 | Eaves 3 | N/A | No (unless over 4m depth under temporary rule) |
| Single-storey rear | Semi-detached or terraced | 4 | 6 | Eaves 3 | N/A | Yes, if over 4m depth under temporary rule |
| Two-storey rear | Any | 7 from rear boundary | 7 from rear boundary (no change) | Ridge must not exceed house ridge | N/A | Yes, if within 3m of rear boundary |
| Side extension | Any | N/A | N/A | Eaves 3, ridge 4 | Half original house width | No |
Source: GOV.UK, 2026 and DESNZ 2024 Order.
The direct answer to “Do you need planning permission for extension UK?”
You do not need planning permission for a single-storey rear extension up to 6 metres (detached) or 4 metres (semi-detached or terraced) under standard permitted development, or up to 8 metres or 6 metres under the temporary rule through May 2027, provided your property is not a flat, listed, or in a protected area, and you meet all other PD conditions on height, roof pitch, materials, and no balconies. If your extension exceeds those dimensions, is forward of the front wall, or your property is in a conservation area or is listed, you must apply for planning permission from your local council (GOV.UK, 2026).
Around 60% of single-storey rear extensions in England are carried out under permitted development, according to Ministry of Housing data. However, you should always check your specific property’s PD eligibility before starting work, as local designations can override the national rules.
How to confirm your extension is permitted development using MCS, Building Regulations, and the Lawful Development Certificate
Permitted development is not the same as Building Regulations approval. You still need Building Regulations compliance for structural safety, fire safety, and energy efficiency. This is checked by your local authority building control or an approved inspector (GOV.UK, 2026).
If you want a formal legal record that your extension is PD, apply for a Lawful Development Certificate (LDC) from your local planning authority. The 2026 fee is approximately £103. An LDC is optional but can be useful when selling your home, as it provides proof that the extension was lawful without planning permission (GOV.UK, 2026).
For extensions involving new windows or doors, you need Building Regulations compliance for glazing (Part L) and structural openings. For gas or heating work, use a Gas Safe Register engineer. For electrical work, use a NICEIC or NAPIT-registered electrician (Gas Safe Register, 2026; NICEIC, 2026). MCS certification is not required for the extension itself, but if you include a heat pump or solar panels, the installer must be MCS-certified to qualify for the Boiler Upgrade Scheme or Smart Export Guarantee (MCS, 2026).
Understanding Building Regulations for home extensions
Frequently Asked Questions
Under permitted development, a single-storey rear extension can be up to 6m deep for a detached house and 4m for a semi-detached or terraced house. The temporary 2024 rule increases these to 8m and 6m respectively until May 2027 (GOV.UK).
Yes, unless it meets permitted development conditions: single-storey, no wider than half the original house width, and with a maximum eaves height of 3m. Side extensions must also not be forward of the principal elevation (GOV.UK, 2026).
The 2024 temporary rule increases permitted rear extension depths to 8m for detached houses and 6m for semi-detached or terraced houses. It applies only to single-storey rear extensions and expires on 30 May 2027 unless renewed (DESNZ / Ministry of Housing, 2024).
Yes, unless it meets permitted development conditions: it must be rear of the principal elevation, within 7m of the rear boundary, and no closer than 3m to the rear boundary. Two-storey extensions also cannot be higher than the existing roof ridge line (GOV.UK).
Permitted development does not apply to properties in conservation areas, Areas of Outstanding Natural Beauty, or National Parks. You must submit a full planning application for any extension in these locations (GOV.UK, 2026).
If your extension exceeds permitted development limits or breaches conditions, you may need to apply for retrospective planning permission. The council can issue an enforcement notice requiring you to alter or remove the extension (GOV.UK).
