Permitted development: what you can build without planning permission

Permitted development lets you extend or alter a house without applying for planning permission, as long as the work stays inside limits set in law. In England that means a single-storey rear extension of 3 metres on most houses and 4 metres on a detached one. We set out the limits project by project, where the rights do not apply, what prior approval and a lawful development certificate cost, and how Wales, Scotland and Northern Ireland differ.

What permitted development is

Permitted development rights are a planning permission granted nationally, so work that fits them needs no application to the council. In England they sit in Part 1 of Schedule 2 to the Town and Country Planning (General Permitted Development) (England) Order 2015, split into Classes A to H. Gates, fences and walls are in Part 2.

A project has to meet every limit in every class it touches. A two-storey extension whose roof joins the main roof has to pass Class A for the extension and Class C for the roof, and Class B as well if it adds a dormer.

The limits are measured from the original house: the house as it stood on 1 July 1948, or as it was built if it is newer. Extensions added since then count against the allowance, whether they were built under permitted development or with planning permission.

These rights only matter for work that needs planning permission in the first place. Internal work that does not enlarge the house, such as turning an integral garage into a room, usually needs none, so whether you need planning permission at all is the first question and permitted development the second.

What you can build under permitted development: the limits at a glance

These are the main limits in England, from the government's technical guidance on householder permitted development.

Two rules run through the whole list. Extensions and outbuildings together can cover no more than half of the land around the original house, and no extension or roof enlargement can rise above the highest part of the existing roof. Materials on the outside have to look similar to the house, though a conservatory is exempt from that condition.

Single-storey rear and side extensions

Rear extensions

A single-storey extension can go 3 metres beyond the rear wall of the original house, or 4 metres on a detached house, and be up to 4 metres high. The depth is measured from the base of the original rear wall to the outside face of the new wall, not to the gutter.

The eaves can sit no higher than the eaves of the existing house, and no higher than 3 metres if any part of the extension is within 2 metres of a boundary. Verandas, balconies and platforms raised more than 0.3 metres are not permitted development, although a Juliet balcony with no platform normally is.

Earlier extensions count. The government's own example is a detached house with a 4 metre rear extension already in place: adding another 5 metres takes the total to 9 metres, past the 8 metre maximum, so it needs a planning application.

Side extensions

An extension beyond a side wall must be single storey, no more than 4 metres high and no wider than half the width of the original house, measured at its widest point. A wraparound that fills the corner between the side and the back has to meet the rear limits and the side limits at once.

Each rear wall counts where the back of a house is stepped, so a side return infill on a terrace running the length of a long outrigger can end up more than 3 metres past the main rear wall, which needs prior approval, or past 6 metres, which needs a planning application. In a conservation area it is not permitted development at all, because side extensions are excluded there.

Two-storey rear extensions

An extension of more than one storey can go 3 metres beyond the rear wall and must stay at least 7 metres from the boundary opposite. Its roof pitch has to match the house as far as practicable, and upstairs windows in a side wall must be obscure-glazed and fixed shut below 1.7 metres above the floor. Two-storey side extensions always need planning permission.

Larger rear extensions: prior approval and the neighbours

Outside designated land and sites of special scientific interest, a single-storey rear extension can go to 6 metres, or 8 metres on a detached house, still no more than 4 metres high. The route is prior approval, also called the neighbour consultation scheme:

1. You notify the council of the proposed extension and pay the fee, £249 in England from 1 April 2026.
2. The council notifies the adjoining neighbours and gives them the chance to object.
3. The council assesses the impact of the extension on the neighbouring homes.
4. Work can start once the council says prior approval is not needed, grants it, or 42 days pass without a decision.

Going from 3 to 6 metres doubles the floor area and the build cost with it. A 5 metre wide extension costs about £36,000 to £50,400 with VAT at 3 metres deep and £68,400 to £97,200 at 6 metres, at standard-quality prices per square metre.

Within the standard 3 and 4 metre depths there is no consultation, so a neighbour has no application to object to. What neighbours keep are their rights over a shared wall: in England and Wales you must tell them before building on or near a party wall or boundary, and a party wall agreement is a separate step from anything planning decides.

Loft conversions and roof alterations

A loft conversion that enlarges the roof, such as a dormer or a hip-to-gable, falls under Class B. The added roof space can be up to 40 cubic metres on a terrace and 50 cubic metres on a semi-detached or detached house, counting any earlier roof extension.

• No dormer or other enlargement on a roof slope that forms the front of the house and faces a road.
• The edge of a dormer set back at least 0.2 metres from the eaves as far as practicable, except on a hip-to-gable or where the new roof joins an extension roof.
• Nothing overhanging the outside face of the original walls.
• Side windows obscure-glazed and fixed shut below 1.7 metres above the floor.
• No balconies or roof terraces, and exterior materials similar in appearance to the house.
• No roof enlargement at all in conservation areas, National Parks, areas of outstanding natural beauty, the Broads or World Heritage Sites.

Rooflights come under Class C and can project no more than 0.15 metres from the roof slope, so a rooflight on the front slope can be permitted development where a front dormer cannot. Rear dormer and hip-to-gable loft conversions can fit these rules. A mansard needs an application, and so does anything that raises the ridge.

Outbuildings, garden rooms and driveways

Class E covers buildings in the garden used for something incidental to the house: a shed, a garage, a greenhouse, a home office, a pool, decking up to 0.3 metres high, or an oil tank of up to 3,500 litres. A building attached to the house is an extension, not an outbuilding.

It must be single storey, sit behind the front of the house and keep to the height limits in the table above. There is no floor area limit of its own, but outbuildings and extensions together cannot cover more than half the land around the original house.

Use is the line that matters. A garden room used as an office, gym or studio is incidental to the house; one with a bedroom, bathroom or kitchen is living accommodation and needs planning permission. Nothing goes up under Class E within the grounds of a listed building.

Paving, gravel or a new drive is permitted development under Class F. The one condition applies between the front of the house and the road: over 5 square metres, the surface must be porous, or the rainwater must drain to a lawn, border or other permeable area within the property.

Where permitted development rights do not apply

The limits above assume a house with its full rights intact. Many homes have fewer, or none. Areas of outstanding natural beauty are now called National Landscapes.

Lawful development certificates and fees

Nobody has to approve work that is permitted development, but a lawful development certificate from the council confirms in writing that it is lawful. It is optional, and it is the proof a buyer's solicitor asks for when you sell. In England a certificate for proposed work costs half the householder planning fee, and planning fees rise each April in line with inflation.

Building regulations and party wall rules still apply

Permitted development settles planning and nothing else. The rights do not remove the need for approval under the building regulations or for notices under the Party Wall Act.

Every extension and loft conversion in England needs building regulations approval, whether or not it needed planning permission. The completion certificate that comes at the end is a separate document from a lawful development certificate.

Permitted development in Wales, Scotland and Northern Ireland

Everything above is the England order. Wales, Scotland and Northern Ireland each set their own permitted development rights, so a house in Cardiff, Edinburgh or Belfast follows different limits.

Wales has run its own planning system since 2016. The Welsh Government's extension rules allow no multi-storey rear extensions under permitted development in conservation areas, National Parks, areas of outstanding natural beauty or World Heritage Sites, and give flats and maisonettes no rights.

Scotland's householder rules are set out in planning circular 1/2024. Neither the single-storey nor the taller extension rules apply in a conservation area or to a flat. A single-storey extension will likely need a building warrant, Scotland's version of building regulations approval, and a taller one will.

Northern Ireland's rights are in the Planning (General Permitted Development) Order (Northern Ireland) 2015, which also allows a porch of up to 3 square metres. Rights are restricted for listed buildings, conservation areas and areas of outstanding natural beauty, and work there needs a planning application.