What is permitted development and does it apply to my extension?

The short answer

Permitted development means you may be able to extend your house without applying for full planning permission, provided the extension stays within strict rules on size, height, position, materials and location.

For many simple rear extensions, permitted development can be enough. But it does not apply to every property or every design. Flats, maisonettes, listed buildings, some conservation areas, properties affected by Article 4 directions and homes with previous planning restrictions often need a different route.

Even when your extension is permitted development, you may still need prior approval, a Lawful Development Certificate, building regulations approval, and accurate drawings before work begins.

What is permitted development?

Permitted development rights are planning rules that allow certain types of building work to be carried out without a full planning application. They are designed for common household projects where a full application would usually be disproportionate, such as modest rear extensions, some side extensions, loft conversions and outbuildings.

The key point is that permitted development is still controlled. Your extension must meet all of the relevant conditions. If one condition is missed — for example the extension is too deep, too high, too close to a boundary, or on a restricted property — it may need planning permission.

Does permitted development apply to my extension?

Permitted development may apply if you are extending a house and the work stays within the rules. It is less straightforward if the property is a flat, maisonette, listed building, in a conservation area, or has had permitted development rights removed.

Before assuming your extension is covered, check:

• Your property type — householder permitted development rights generally apply to houses, not flats or maisonettes.
• Your location — conservation areas, National Parks, Areas of Outstanding Natural Beauty, the Broads and World Heritage Sites can have tighter restrictions.
• Your planning history — previous permissions may include conditions removing permitted development rights.
• Article 4 directions — some councils remove specific permitted development rights in sensitive streets or areas.
• The exact design — depth, height, width, roof form, materials and boundary distances all matter.

Permitted development rules for rear extensions

For a standard single-storey rear extension in England, the usual depth limits are:

• Detached houses — up to 4 metres beyond the rear wall of the original house.
• Semi-detached, terraced and other houses — up to 3 metres beyond the rear wall of the original house.

There are also height limits. A single-storey rear extension must not exceed 4 metres in height, and if it is within 2 metres of a boundary, the eaves height must not exceed 3 metres.

The phrase original house is important. It usually means the house as it stood on 1 July 1948, or as it was first built if built after that date. Previous extensions by earlier owners can reduce what you are allowed to build now.

What about larger rear extensions?

Some larger single-storey rear extensions can still be built without a full planning application, but they normally require the larger home extension prior approval process.

This can allow rear extensions of up to:

• 8 metres beyond the rear wall for detached houses.
• 6 metres beyond the rear wall for other houses.

This is not the same as simply building under standard permitted development. Your council must be notified, neighbours are consulted, and the extension cannot proceed unless the prior approval process is satisfied.

What about side extensions?

Side extensions can sometimes be permitted development, but the rules are more restrictive. In general, a side extension must be single storey, no more than 4 metres high, and no wider than half the width of the original house.

On designated land, side extensions are usually not permitted development. Wraparound extensions can also be tricky, because combining side and rear elements may take the design outside the permitted development limits. In many cases, a wraparound extension needs a full householder planning application.

Can a two-storey extension be permitted development?

Some two-storey rear extensions can fall under permitted development, but the rules are tighter than for single-storey extensions. They must normally be at the rear, not exceed 3 metres in depth, sit at least 7 metres from the rear boundary, use materials similar to the existing house, and avoid certain window arrangements that affect neighbours' privacy.

Because two-storey extensions have a bigger impact on neighbours, daylight, privacy and the appearance of the house, it is sensible to check with your local planning authority or apply for a Lawful Development Certificate before committing to the design.

When permitted development does NOT apply

Permitted development does not apply in every situation. You are likely to need planning advice or a full application if:

• You live in a flat or maisonette.
• The property is listed or attached to a listed building.
• The extension would be on designated land where the relevant PD rights are restricted.
• Your council has introduced an Article 4 direction.
• A previous planning permission removed or limited your permitted development rights.
• The extension would cover more than half the land around the original house.
• The proposed materials would not be similar in appearance to the existing property.
• The extension would include a balcony, veranda, raised platform or other feature that falls outside the rules.

Should you get a Lawful Development Certificate?

If you believe your extension is permitted development, it is still often worth applying for a Lawful Development Certificate. This is a formal decision from the council confirming that the proposed work is lawful.

An LDC is especially useful when you come to sell or remortgage the property, because buyers, solicitors and lenders may ask for proof that the extension did not need planning permission. It also reduces uncertainty before builders start work.

To apply, you will normally need clear existing and proposed drawings, a site plan and enough information for the council to assess the proposal against the permitted development rules.

Building regulations still apply

Permitted development only deals with planning permission. It does not remove the need for building regulations approval. Most extensions require building regulations approval because the work affects structure, insulation, drainage, fire safety and energy performance.

Building regulations are separate from planning. An extension can be permitted development for planning purposes and still need detailed technical design, structural input and inspection under building control.

What drawings do you need?

Whether you are applying for a Lawful Development Certificate, prior approval or full planning permission, accurate drawings make the process much smoother. For an extension, you will usually need:

• Existing floor plans — showing the current layout of the house.
• Proposed floor plans — showing the new extension and internal layout.
• Existing elevations — showing the current appearance of the property.
• Proposed elevations — showing the extension, roof form, openings and materials.
• Site plan — showing the property, boundaries and extension location.
• Block plan — often required to show the wider site context.

Good drawings also help builders price the work accurately and reduce misunderstandings once the project is on site.

How to check before you build

The safest way to check whether permitted development applies is to look at the rules for your exact property and your exact design. Do not rely on a neighbour's extension as proof, because their property type, planning history or boundary position may be different.

Before starting work:

• Check your local council's planning map for conservation areas and Article 4 directions.
• Review your property's planning history for conditions affecting permitted development rights.
• Check whether the property is listed.
• Measure the extension from the original rear wall, not just the current rear wall.
• Prepare drawings and consider applying for a Lawful Development Certificate.

Summary

Permitted development can make many home extensions quicker and simpler because a full planning application may not be needed. However, the rules are detailed and depend on the property, location and design.

For a typical single-storey rear extension, permitted development may apply if the extension stays within the relevant depth, height, boundary and design limits. Larger rear extensions may need prior approval, and side, wraparound or two-storey extensions often require closer checking.

Even when planning permission is not required, drawings are still important — both for checking the rules and for giving the council, builder and building control a clear record of the proposed work.