Frequently Asked Questions About Rear Extensions and Permitted Development

Planning rules can often feel complicated, especially if you're starting your first home improvement project. Below are answers to some of the questions we're asked most often by homeowners considering a rear extension.

Can I build a rear extension without planning permission?

In many cases, yes. If your property benefits from Permitted Development Rights and your proposed extension complies with the relevant size, height and design restrictions, you may not need to submit a full planning application.

However, every property is different, so it's important to check whether any planning conditions or Article 4 Directions affect your home before work begins.

How far can I extend my house under Permitted Development?

For most properties, the standard limits are:

• Up to 3 meters from the original rear wall for terraced and semi-detached houses.

• Up to 4 meters for detached houses.

Larger extensions may also be possible under the Larger Home Extension scheme, provided additional procedures are followed.

What is meant by the "original house"?

The "original house" refers to the property as it was first built, or as it stood on 1 July 1948 if it was constructed before that date.

This is important because any extensions added after this point may count towards your Permitted Development allowance, even if they were built by a previous owner.

Can I extend an existing extension?

Yes, in many cases you can.

However, the combined development must still comply with all Permitted Development rules. Existing extensions don't reset your allowance, so it's essential to consider the property's entire planning history before designing further additions.

Do I need Building Regulations approval?

Almost certainly.

Even if planning permission isn't required, most rear extensions still need Building Regulations approval to ensure they meet current standards for structure, insulation, drainage, fire safety and energy efficiency.

Planning permission and Building Regulations are completely separate legal requirements.

Do I need my neighbour's permission?

Not usually for planning purposes.

However, if your extension affects a shared wall or is built close to a neighbouring boundary, the Party Wall etc. Act 1996 may apply.

It's also good practice to discuss your plans with neighbours before work starts, particularly if construction is likely to cause temporary disruption.

Can I build a wraparound extension under Permitted Development?

In most cases, no.

Because wraparound extensions include both rear and side elements, part of the proposal is often assessed under the rules for side extensions. This frequently means a full planning application is required.

Every property is different, so obtaining professional advice before finalising your design is recommended.

Do sheds and garages count towards the 50% rule?

Yes.

When calculating the amount of land that has been developed around your property, existing outbuildings such as garages, sheds and other permanent structures are normally included.

This is one of the reasons it's important to assess the entire site rather than focusing solely on the proposed extension.

Can I build a rear extension if I live in a Conservation Area?

Possibly.

Many homes within Conservation Areas still benefit from certain Permitted Development Rights, but additional restrictions often apply. Larger or two-storey extensions are more likely to require planning permission.

The exact rules depend on your property's location and planning history.

Is a Lawful Development Certificate compulsory?

No.

A Lawful Development Certificate (LDC) is optional, but many homeowners choose to obtain one because it provides formal confirmation that the extension was lawful when built.

This can be particularly useful when selling your property, as buyers and solicitors often request evidence that development was carried out legally.

What happens if I build without checking the rules?

Constructing an extension that doesn't comply with planning legislation can have serious consequences.

Your local planning authority may require changes to the development, request a retrospective planning application or, in some cases, take enforcement action.

Taking advice before work starts is almost always quicker, less expensive and far less stressful than trying to resolve planning issues after construction has begun.

Still Unsure About Your Extension?

Every property has its own planning history, and even houses that appear identical can be subject to different restrictions.

If you're unsure whether your proposed rear extension qualifies under Permitted Development, seeking professional advice before construction begins can save considerable time, money and uncertainty. A planning assessment at the design stage can identify potential issues early and help you move forward with confidence.

Whether you're planning a modest kitchen extension or a larger family living space, understanding the rules before you build is the best way to ensure your project runs smoothly from start to finish.