Do I need planning permission? A decision guide
Which home projects need planning permission in England and which do not, the homes where the answer changes, what a definite answer costs, and how Wales, Scotland and Northern Ireland differ.
Most extensions, lofts, porches and garden buildings on a house in England need no planning application, because permitted development covers them. New buildings, bigger extensions and changes of use need one. We answer project by project, list the homes where the answer changes, price a definite answer and cover Wales, Scotland and Northern Ireland.
What needs planning permission
The gov.uk planning guide for England and Wales says you will probably need planning permission to build something new, to make a major change such as an extension, or to change the use of a building. Your local council decides.
The legal test is section 55 of the Town and Country Planning Act 1990: works that affect only the inside of a building, or do not materially change how it looks outside, are not development. So a new kitchen needs no planning permission, though a new bathroom or fuse box needs building regulations approval, as does every extension and loft conversion in England. Splitting one house into 2 or more homes is a material change of use, which is development.
House projects that usually need no application
Most house projects that need no application in England are permitted development: planning permission granted nationally by the General Permitted Development Order 2015, as long as the work stays inside fixed limits.
| Project | Application needed? | What decides it |
|---|---|---|
| Single-storey rear extension | Usually no | 3 m deep, 4 m if detached, max 4 m high; 6 m or 8 m with prior approval |
| Side extension | Usually no | Single storey, max 4 m high, no wider than half the house; yes on designated land |
| Two-storey extension | Rear usually no, side yes | Rear: 3 m deep, at least 7 m from the rear boundary |
| Loft dormer or hip-to-gable | Usually no | Up to 40 m³ added on a terrace, 50 m³ on other houses; no front dormer facing a road |
| Rooflights | Usually no | Project 0.15 m or less from the roof |
| Porch | Usually no | Up to 3 m² and 3 m high, at least 2 m from a boundary with a road |
| Conservatory | Usually no | Same limits as an extension |
| Garage conversion | Usually no | Internal work, with the house not enlarged |
| Shed or garden room | Usually no | Single storey, behind the house front; eaves 2.5 m; 4 m high with a dual-pitched roof, 3 m otherwise, 2.5 m within 2 m of a boundary |
| Driveway or front paving | Usually no | Over 5 m²: porous, or draining to a lawn or border |
| New kitchen or internal walls | No | Not development |
| Splitting a house into flats | Yes | A material change of use |
Depths are measured from the original house: the house as it stood on 1 July 1948, or as built if newer. A previous owner's extension counts against your allowance, and extensions and garden buildings together can cover no more than half the land around the original house.
Four projects turn on a detail the table cannot hold:
- A conservatory is an extension in planning terms, with the same limits, though its materials need not match the house.
- Converting a garage into a room is usually internal work, but the right is sometimes removed, particularly on newer housing developments.
- A garden room used as an office or gym is an outbuilding; with a bedroom, bathroom or kitchen it needs an application.
- A mansard, a raised ridge or a roof enlargement on designated land means applying for planning permission for a loft conversion.
Homes where the answer changes
The table assumes a house with its full rights. These homes have fewer, or none:
- Flats and maisonettes: no householder permitted development, so extensions, lofts and garden buildings need an application.
- Houses converted from a shop or farm building under permitted development: usually no householder rights.
- Listed buildings: listed building consent may be needed, and no garden building goes up under permitted development in the grounds.
- Designated land (conservation areas, National Parks, National Landscapes, the Broads and World Heritage Sites): no side extensions, two-storey rear extensions, roof enlargements, cladding or prior approval extensions.
- Article 4 directions and planning conditions: either can remove named rights, so check the estate's original permission on any newer house.
How to get a definite answer
A council's online checker gives guidance based on your answers, not a decision you can rely on later. An answer that holds comes from checking the address itself.
Planning fees and decision times in England
Planning fees in England are set nationally and rise every 1 April. Most applications are decided within 8 weeks, or 13 for unusually large or complex ones, and an appeal against a refusal can take several months.
Against what the extension will cost, every fee here is small: a 30 square metre single-storey extension at standard quality runs £68,400 to £97,200 with VAT.
Prior approval takes less time than an application: the council notifies the neighbours, who can object, and work can start if it has not decided within 42 days.
What happens if you build without planning permission
Work that needed permission and went ahead without it can draw an enforcement notice ordering you to undo all the changes. Under section 171B of the 1990 Act, the council has 10 years from substantial completion to act in England and 4 in Wales.
The question also comes back when you sell, because the buyer's solicitor asks for proof the work was lawful.
Planning permission in Wales, Scotland and Northern Ireland
| Nation | Limit | Building approval |
|---|---|---|
| England | 3 m, or 4 m detached; 6 m or 8 m with prior approval; max 4 m high | Building regulations approval |
| Wales | 4 m beyond the rear wall; max 4 m high | Building regulations, Welsh Approved Documents |
| Scotland | Within 1 m of a boundary: 3 m on a terrace, 4 m on other houses; max 4 m high | Building warrant |
| Northern Ireland | 4 m detached, 3 m on other houses | Separate NI building control |
Wales has run its own planning system since 2016. Welsh flats have no permitted development rights, and designated areas allow no multi-storey rear extensions without an application.
Scotland's planning guidance gives the same 3 reasons for needing permission and adds conservation area consent and listed building consent. Permitted development extensions are ruled out for flats and in conservation areas, and a building warrant will likely be needed.
Northern Ireland runs separate planning and building control, and work there to a listed building, in a conservation area or in an area of outstanding natural beauty needs planning permission.
Common questions
What is allowed without planning permission?
In England a house can usually have a 3 metre single-storey rear extension, or 4 metres if detached, a loft dormer adding up to 40 or 50 cubic metres, a porch of up to 3 square metres and single-storey garden buildings without planning permission. Flats and listed buildings have fewer rights or none.
How can I find out if I need planning permission?
Your local council decides, and a lawful development certificate, £274 in England from 1 April 2026, is the definite answer for proposed work. An online checker gives guidance only, so search the council's planning register for conditions on your address.
Can you start building work without planning permission?
You can start permitted development work without a planning application. Work that needed permission and went ahead without it can draw an enforcement notice ordering it undone, and the council has 10 years to act in England and 4 in Wales.
At what point do I need planning permission?
You need planning permission once a project builds something new, goes past the permitted development limits, or changes a building's use. In England that includes a rear extension deeper than 3 metres, or 4 metres detached, without prior approval, any two-storey side extension, and splitting a house into flats.
Do I need planning permission for a porch?
A porch in England needs no planning permission if its ground area is no more than 3 square metres, no part is over 3 metres high, and it sits at least 2 metres from a boundary with a road or footpath. A bigger porch needs a £548 householder application.