Permitted development for houses: extensions, loft conversions and lawful development certificates
KRAMAN Ltd. Published 29 October 2026. Rules checked on 29 October 2026 against the government guidance and legislation listed under Sources below.
A house in England can be extended without a planning application within the limits of the General Permitted Development Order. The main limits are a single-storey rear extension of up to 3 metres, or 4 metres for a detached house, and 4 metres high, or up to 6 or 8 metres through prior approval, and a loft extension adding up to 40 cubic metres to a terrace house or 50 to other houses. Flats have no such rights, and conservation areas, Article 4 directions and conditions on earlier permissions can remove them. A lawful development certificate from the council, decided within 8 weeks, confirms that a proposal is lawful.
Does your house have permitted development rights?
- House or flat. The rights apply to houses. A building containing flats, or a single flat in a building, is not a dwellinghouse for these rules.
- Conservation area. Conservation areas count as article 2(3) land, where roof extensions, side extensions, rear extensions of more than one storey and the prior approval route are not available. See what needs planning permission in a conservation area.
- Article 4 direction or planning condition. A council can remove rights with an Article 4 direction, and an earlier planning permission for the house may carry a condition that removed them.
- The original house. Limits are measured from the original house: as it stood on 1 July 1948, or as first built if later. Earlier extensions count against the allowance.
Extensions (Class A)
The table lists the key limits. The technical guidance sets out every condition in full, and all of them must be met.
| Extension | Limit without a planning application |
|---|---|
| Single-storey rear extension | Up to 3 metres beyond the rear wall of the original house, or 4 metres for a detached house, and no more than 4 metres high |
| Larger single-storey rear extension | Up to 6 metres, or 8 metres for a detached house, through prior approval. Not on article 2(3) land or a site of special scientific interest |
| Rear extension of more than one storey | Up to 3 metres beyond the rear wall, and at least 7 metres from the boundary opposite the rear wall |
| Side extension | Single storey, under 4 metres high and no wider than half the width of the original house |
| Front and road-facing side | No extension beyond the principal elevation of the original house, usually its front, or beyond a side elevation that fronts a highway, which matters on corner plots |
| Eaves | No higher than the eaves of the existing house, and no higher than 3 metres within 2 metres of a boundary |
| Height and garden coverage | No higher than the highest part of the existing roof. Extensions and outbuildings together can cover no more than half of the land around the original house |
| Conditions | Materials of similar appearance to the house. Upper-floor windows in a side wall obscure glazed and non-opening below 1.7 metres from the floor. No verandas, balconies or raised platforms |
The prior approval route for larger extensions
A single-storey rear extension of 3 to 6 metres, or 4 to 8 metres for a detached house, is permitted only after you notify the council and it decides whether prior approval is needed. The council gives the adjoining neighbours notice of the proposal and the chance to object. Work can start once the council says prior approval is not required or gives it, or once 42 days pass without a decision. The 42 days do not waive anything else: the extension must still meet every other Class A limit and condition. The route is not available in a conservation area. For the options on a terrace or semi, see our house extension page.
Loft conversions (Class B)
| Rule | Limit without a planning application |
|---|---|
| Extra roof space | Up to 40 cubic metres on a terrace house, 50 cubic metres on other houses |
| Front roof slope | No dormer on the principal elevation that fronts a highway |
| Height and set-back | Nothing higher than the highest part of the existing roof. The enlargement stays at least 0.2 metres back from the eaves, unless that is not possible for practical or structural reasons |
| Conditions | Materials of similar appearance. Side-facing windows obscure glazed and non-opening below 1.7 metres from the floor. No verandas, balconies or raised platforms |
| Conservation areas | Roof extensions are not permitted development and need planning permission |
A mansard usually goes beyond these limits and needs planning permission. Converting a loft into a liveable room always needs building regulations approval, and steel beams bearing into a shared wall need notice under the Party Wall Act. For loft types and layouts, see our loft conversion page.
Lawful development certificates
A lawful development certificate is a decision from the council that a use or building work is lawful for planning purposes. There are two kinds: one for an existing use or work already done, under section 191 of the Town and Country Planning Act 1990, and one for proposed work, under section 192.
- It is voluntary. Anyone can apply to the council, with enough information for the council to decide and a precise description of the proposal.
- The council must decide within 8 weeks of receiving the application, unless a longer period is agreed in writing.
- A certificate for proposed work means work carried out as described is presumed lawful, unless something material changes before the work begins, such as an Article 4 direction that removes the relevant right or a change to the permitted development rules.
- A refusal can be appealed to the Secretary of State.
- It does not cover building regulations or listed building consent, and it can be revoked if it was based on false or misleading information.
What permitted development does not cover
- Building regulations approval, which most extensions and every loft conversion need.
- Notices under the Party Wall etc. Act 1996 for work on or near a shared wall.
- Listed building consent, if the house is listed. See our listed building restoration page.
- Flats, which have no householder permitted development rights.
Frequently asked questions
How far can I extend my house without planning permission?
A single-storey rear extension can go 3 metres beyond the rear wall of the original house, or 4 metres for a detached house, up to 4 metres high. Outside conservation areas and other article 2(3) land, the prior approval route allows up to 6 metres, or 8 metres for a detached house. A rear extension of more than one storey can go 3 metres back and must stay at least 7 metres from the rear boundary.
Do I need planning permission for a loft conversion?
Not if the house keeps its permitted development rights and the loft stays within the limits: up to 40 cubic metres of extra roof space on a terrace house and 50 on other houses, no dormer on the front roof slope facing a highway, nothing higher than the existing roof and no balcony. Roof extensions in a conservation area need planning permission. Every loft conversion into a liveable room needs building regulations approval.
Can I build a two-storey extension without planning permission?
A rear extension of more than one storey can be permitted development if it extends no more than 3 metres beyond the rear wall of the original house and stays at least 7 metres from the rear boundary, with the other Class A conditions met. In a conservation area it needs planning permission.
Do flats have permitted development rights?
No. Householder permitted development rights apply to houses. The definition of a dwellinghouse does not include a building containing flats or a single flat within a building, so external changes to a flat usually need planning permission.
Do I need a lawful development certificate?
It is not compulsory. Anyone can apply to the council for one, and a certificate for proposed work means the work, if carried out as described, is presumed lawful, unless something material changes before the work begins, such as an Article 4 direction removing the relevant right or a change to the permitted development rules.
How long does a lawful development certificate take?
The council must give its decision within 8 weeks of receiving the application, unless you agree a longer period in writing.
Sources
- Permitted development rights for householders: technical guidance, Ministry of Housing, Communities and Local Government
- The Town and Country Planning (General Permitted Development) (England) Order 2015, Schedule 2, Part 1
- Lawful development certificates, GOV.UK planning practice guidance
- The Town and Country Planning (Development Management Procedure) (England) Order 2015, article 39
This guide summarises the national rules for houses in England. It is general information, not a planning decision: the council decides each case, so confirm your proposal with the council or apply for a lawful development certificate.
Planning an extension or loft conversion?
Call 07717 778 612 or send us a brief. The initial site visit is free, and every estimate is individual.