Often not. Many single-storey rear and side extensions in England are permitted development, so no planning application is needed, provided they stay within set limits on size, height and position. Flats, conservation areas, listed buildings and homes with Article 4 directions follow stricter rules, and you still need Building Regulations approval either way.
What is permitted development?
Permitted development, often called PD rights, is a national grant of planning permission for certain types of household work. It is set out in the General Permitted Development Order. If your extension fits inside every limit and condition, you don't need to apply to the council for planning permission.
The limits are measured against the 'original house' – the house as it was first built, or as it stood on 1 July 1948 if it is older. That matters, because an extension added by a previous owner counts towards your allowance. PD rights for extensions apply to houses, not to flats or maisonettes, and some newer estates had them removed by a planning condition when they were built.
How big can an extension be without planning permission?
These are the main limits for a house in England. Every one has to be met. If you fail one, you need to apply.
- Single-storey rear extensions can project up to 3 m beyond the original rear wall of a semi-detached or terraced house, or up to 4 m for a detached house, and can be up to 4 m high.
- No extension can be higher than the highest part of the existing roof, or higher at the eaves than the existing eaves. Within 2 m of a boundary, the eaves can't be more than 3 m high.
- Side extensions must be single storey, no more than 4 m high and no wider than half the width of the original house.
- Extensions of more than one storey can project up to 3 m beyond the original rear wall and must be at least 7 m from the boundary opposite the rear wall.
- Nothing can be built forward of the principal elevation (usually the front), or of a side elevation that faces a road.
- Extensions and outbuildings together can't cover more than half the land around the original house.
- No verandas, balconies or raised platforms are allowed, and external materials must look similar to the existing house.
- On a two-storey extension, upper-floor windows in a side wall must be obscure-glazed and non-opening unless the opening part is more than 1.7 m above the floor. The roof pitch should match the house as far as practicable.
What is prior approval for a larger home extension?
Outside conservation areas and other designated land, you can build a single-storey rear extension of up to 6 m on a semi or terrace, or 8 m on a detached house, through a lighter process called prior approval. It isn't a full planning application, but you must apply and wait before starting.
You send the council a description of the extension with its depth, maximum height and eaves height, a plan, and the addresses of your neighbours. The council writes to adjoining neighbours, who get at least 21 days to comment. If anyone objects, the council judges the effect on their amenity. The legislation gives the council 42 days. If it hasn't told you its decision by then, the work can go ahead as described. From 1 April 2026 the fee in England is £249. Some councils also provide a form for telling them when the work is finished, so check what yours asks for.
Should I get a lawful development certificate?
A lawful development certificate (LDC) is a legal document from the council confirming that a proposed or existing project is lawful. For a permitted development extension it isn't compulsory, but it is the formal way to prove the work didn't need planning permission.
It is worth having if you are close to any limit, if the house has been extended before, or if you plan to sell, because buyers' solicitors often ask for evidence. From 1 April 2026 an LDC for proposed work costs half the normal householder fee, which is £274 in England. It is not a replacement for planning permission. If it is refused, you may need to apply.
When do conservation areas and Article 4 directions change the rules?
Some land is 'Article 2(3) land': conservation areas, National Parks, Areas of Outstanding Natural Beauty, the Broads and World Heritage Sites. On this land, side extensions and rear extensions of more than one storey always need planning permission, cladding such as render, stone, timber or tiles isn't permitted development, and the larger home extension route isn't available.
Separately, a council can make an Article 4 direction that removes some or all PD rights in a defined area. If your home is listed, you need listed building consent for significant works inside or out, whatever the planning position. None of this is obvious from the street, so check with the council before you pay for drawings.
Which council deals with it, and how long does a planning application take?
Planning is handled by your local planning authority. Across the West Midlands that is the city, borough or district council: Birmingham, Sandwell, Dudley, Walsall, Wolverhampton, Solihull or Coventry, for example. In Staffordshire, Worcestershire and Warwickshire, householder applications currently go to the district or borough council, not the county council.
The council normally has 8 weeks to decide a householder application. From 1 April 2026 the fee for extending a single house in England is £548. If permission is granted, you normally have three years to start. Building something that needed permission without getting it can lead to an enforcement notice requiring you to alter or remove the work.
Do I still need Building Regulations approval and a party wall notice?
Yes. These are separate from planning. Almost every extension needs Building Regulations approval for structure, fire safety, insulation, drainage and ventilation, whether or not it needs planning permission. If you are building on or near a shared boundary, or digging foundations close to a neighbour's, the Party Wall etc. Act 1996 may also require you to serve notice.
Planning Portal guidance is introductory and local rules vary. Treat this guide as a starting point, and confirm your own case with the council or a planning professional before you commit to a design.
Sources
- Planning Portal – Extensions: planning permission
- legislation.gov.uk – GPDO 2015, Schedule 2, Part 1, Class A (house extensions)
- Planning Portal – Lawful development certificate
- GOV.UK – Planning fees: annual indexation from 1 April 2026
This guide is general information for homes in England, not legal or professional advice for your property. Rules change — check with your council or the Planning Portal before you rely on it.