Many single-storey rear extensions and loft conversions can be built under permitted development, but conservation areas, flats, earlier extensions and Article 4 directions all change the answer. Here is how to work out where your project sits.
The short answer: many single-storey rear extensions and loft conversions in Cheshire and South Manchester can be built under permitted development, without a full planning application. Double-storey, wraparound and side extensions more often need planning permission, and homes in conservation areas, flats and some newer estates have fewer or no permitted development rights.
This guide summarises the national rules for houses in England at the time of writing (last reviewed September 2026). The rules are detailed and do change, so always confirm the position for your address with the council or through a lawful development certificate before you build.
What is permitted development?
Permitted development rights are a national grant of planning permission for certain types of work to houses, provided the work stays within set limits and conditions. They exist so that modest, predictable projects do not need a full application. They apply to houses, not flats or maisonettes, and they can be removed or restricted in some places.
Which extensions can be permitted development?
For a single-storey rear extension, the basic limits are a depth of 3 metres beyond the original rear wall for an attached house, or 4 metres for a detached house, and a maximum height of 4 metres. Under the larger home extension scheme, those depths can increase to 6 and 8 metres, but you must first apply to the council for prior approval, and neighbours are consulted.
Other key conditions include:
- The extension cannot go beyond the front of the house, or the side if that side faces a road.
- If it is within 2 metres of a boundary, the eaves cannot be higher than 3 metres.
- Extensions and outbuildings together cannot cover more than half the garden area around the original house.
- Side extensions must be single storey, no more than 4 metres high and no wider than half the width of the original house.
- Two-storey rear extensions are limited to 3 metres in depth and must be at least 7 metres from the rear boundary.
- Materials should be similar in appearance to the existing house.
Note the word original. It means the house as first built, or as it stood on 1 July 1948 if older. Any earlier extensions, even ones built decades ago by previous owners, count towards the limits.
What about loft conversions?
Loft conversions can often be permitted development if the extra roof space is no more than 40 cubic metres for a terraced house or 50 cubic metres for a semi-detached or detached house. Dormers cannot face the road at the front, the extension cannot be higher than the existing ridge, side-facing windows must be obscure glazed and fixed below 1.7 metres, and dormers should normally be set back from the eaves.
When do I need full planning permission?
You will normally need planning permission if your project goes beyond the permitted development limits, if your house is a flat or maisonette, if permitted development rights have been removed, or if you are in a designated area where the rules are tighter. Most double-storey side and wraparound extensions fall into this category.
Conservation areas
Conservation areas cover parts of many local towns and villages, including Alderley Edge, Prestbury, Knutsford, Didsbury and parts of Altrincham and Chorlton. In a conservation area, side extensions, two-storey rear extensions, roof extensions such as dormers and cladding are not permitted development, so they need planning permission. Listed buildings need listed building consent for most changes, inside as well as out.
Article 4 directions and planning conditions
Councils can remove specific permitted development rights in an area through an Article 4 direction. Separately, many newer estates were approved with a planning condition that removed permitted development rights for extensions or garage conversions. These do not show up on the ground, so we check the planning history of the property before recommending a route.
Green Belt
Much of the countryside around Wilmslow, Prestbury, Alderley Edge and Knutsford is Green Belt. Permitted development still applies to houses in the Green Belt, but where you need planning permission, extensions are assessed against whether they are disproportionate to the size of the original building. Earlier extensions count against you here too.
Which council decides my application?
It depends on where you live. Wilmslow, Alderley Edge, Prestbury and Knutsford are in Cheshire East. Bramhall, Cheadle Hulme and Stockport are in Stockport. Altrincham, Hale and Sale are in Trafford. Didsbury and Chorlton are in Manchester. Each council has its own local policies and design guidance, which shape what is approved beyond the national rules.
Should I get a lawful development certificate?
If you are relying on permitted development, a lawful development certificate from the council confirms that the work is lawful. It is not compulsory, but we usually recommend it. Buyers' solicitors often ask for one when you sell, and it removes any doubt before you spend money on the build.
Planning is not the same as building regulations
Whichever planning route applies, almost every extension and loft conversion needs building regulations approval. Building regulations cover structure, fire safety, insulation, ventilation and drainage. Structural calculations form a key part of that, and at Everstone they are prepared in-house by our Chartered Engineer director.
Not sure whether your project needs planning permission? Our free feasibility check tells you where your project is likely to sit before you pay for drawings.