If the works fully comply with permitted development rules, full planning permission may not be required.

However, we usually recommend applying for a Lawful Development Certificate before building so you have formal written confirmation from the council.

No. Planning permission involves the council assessing the proposal against planning policy.

A Lawful Development Certificate confirms whether the proposal is lawful under permitted development or other planning rules.

It is not always compulsory, but it is strongly recommended.

It can help avoid future problems with the council, neighbours, solicitors, lenders or buyers.

Flats and maisonettes do not benefit from the same householder permitted development rights as houses.

If you live in a flat or maisonette, planning permission is more likely to be required for external alterations (even changing windows) or extensions.

Sometimes, but the rules are more restricted.

Conservation areas can limit certain works, particularly roof extensions, side extensions, cladding and works visible from public areas.

Some areas may also be affected by Article 4 Directions.

It’s therefore normally safer to use the full planning application route.

An Article 4 Direction is a planning restriction that removes certain permitted development rights in a defined area.

If your property is affected, you may need planning permission for works that would otherwise have been permitted development.

Yes. Previous extensions and alterations can count towards the permitted development limits, even if they were built by a previous owner.

This is one of the key reasons to check the planning history before relying on permitted development.

Many garden rooms can be built under permitted development if they are incidental to the main house and comply with the relevant limits.

However, a building used as a separate dwelling, sleeping accommodation or independent living space is unlikely to be treated as a simple outbuilding.

You can, but it carries risk.

If the council later decides the works were not lawful, you may need to apply for retrospective planning permission or alter the works.

We usually recommend obtaining the certificate before construction starts.

If the council refuses the certificate, we will review the reasons and advise on the next steps.

This may involve amending the design, submitting a full planning application or considering whether the council’s decision can be challenged.

The preparation time depends on the complexity of the project and whether a measured survey is required.

Once the drawings and application documents are ready, the council assessment period is usually around 8 weeks. This timescale starts once the application has been submitted and validated by the council.

The council application fee is usually around £370, although this should always be checked at the time of submission as fees can change.

Our fee depends on the project type, the drawings required and whether a site survey is needed. We will confirm our fee following your enquiry once we understand the property and proposed works.

For many single-storey rear extensions, the usual permitted development depth limits are:

• Up to 3 metres for a terraced or semi-detached house
• Up to 4 metres for a detached house

Larger rear extensions may sometimes be possible through the prior approval process, but this is not the same as standard permitted development and neighbours will be consulted.

For many single-storey rear extensions, the maximum height is usually 4 metres, with a maximum eaves height of 3 metres.

In some cases, a two-storey rear extension can be considered under permitted development, but the rules are much more restrictive.

It usually must not be within 2 metres of a boundary and it must not connect to other existing extensions in a way that takes it outside the permitted development limits. Because of this, two-storey permitted development extensions are often not suitable for typical London properties.

A side extension may be possible under permitted development if it complies with the relevant rules.

As a general guide, the width of the side extension must not be more than half the width of the original house. It also usually cannot be used on corner plots where the extension would be on land forward of a side elevation facing a highway.

Usually, no.

A rear extension and a side extension can sometimes each be considered under permitted development, but they generally cannot join together to form a wraparound extension. If the side and rear elements touch, the proposal is likely to fall outside permitted development and a full planning application may be required.

This can be a problem.

Permitted development rights are assessed against the original house and previous extensions. If the new extension touches, connects to or combines with an existing extension, it may take the proposal outside permitted development limits.

This is particularly important on properties that have already been extended by a previous owner.

L-shaped houses can be more complicated.

If part of the original house projects to the rear or side, a proposed extension may touch what is technically a side wall. This can mean the extension is treated as a side extension, or as exceeding the permitted width limits, even if it looks like a rear extension on plan.

This is a common reason why a simple-looking extension may not qualify under permitted development.

F

or roof extensions, the permitted development volume allowance is usually:

• 40 cubic metres for terraced houses, including end-of-terrace houses
• 50 cubic metres for semi-detached and detached houses

This allowance includes any previous roof additions. If the roof has already been extended, the remaining volume may be reduced or used up completely.

This can be difficult and often may not qualify under permitted development.

Corner plots need careful review because works to a roof slope or elevation facing a highway can fall outside permitted development. A hip-to-gable extension on a corner property is therefore more likely to require a full planning application.

Permitted development rules are set nationally, not by each individual council.

However, councils still assess whether a proposal complies with the national rules when deciding a Lawful Development Certificate application. Local factors can also affect the position, such as conservation areas, Article 4 Directions, planning conditions and the planning history of the property.

A typical Lawful Development Certificate application requires:

• Existing and proposed floor plans
• Existing and proposed elevations
• Existing and proposed roof plans, where relevant
• A site location plan
• A block plan
• Application form
• Description of the proposed works
• Volume calculations for roof extensions, where relevant
• Supporting information explaining why the works are lawful

The exact requirements depend on the project type.

A Lawful Development Certificate does not normally expire in the same way as planning permission.

However, it confirms the lawfulness of the specific works shown and described in the application, based on the planning rules and circumstances at the relevant time. If the national rules change, the property changes, area becomes a conservation area, or the works carried out are materially different from the approved certificate, the position may need to be reviewed.