Do I Need Planning Permission for a Rear Extension in the UK?

If you're planning a house extension in Harrogate, one of the first questions homeowners ask is whether planning permission is required. As a provider of architectural drawings in Harrogate, I regularly help clients underatnd local planning rules...

If you’re planning a rear extension, one of the first questions you’ll ask is whether you need planning permission. The answer is sometimes yes, sometimes no — and getting it wrong can cost time, money, and stress.

This guide explains when planning permission is required, when an extension falls under permitted development, and how drawings fit into the process.

The short answer

You may not need planning permission for a rear extension if it meets permitted development (PD) rules.

However, many extensions do require permission, especially if:

• The property is not a house

• It’s in a conservation area

• The extension exceeds size limits

• Previous extensions have used up PD rights

When in doubt, professional drawings and advice can save months of delays.

Rear Extension Planning Permission Rules in Harrogate

Permitted development rights allow homeowners to extend their property without submitting a full planning application, as long as strict rules are followed.

For rear extensions, the main rules are:

Detached houses

• Up to 4 metres deep (single storey)

• Up to 8 metres with prior approval

Semi-detached and terraced houses

• Up to 3 metres deep (single storey)

• Up to 6 metres with prior approval

Other key limits include:

• Maximum height of 4 metres

• Materials must be similar to the existing house

• Extension must not cover more than 50% of the original garden

When planning permission is required

You will usually need planning permission if:

• The extension exceeds permitted development limits

• It is two storeys

• The property is a flat or maisonette

• The house is listed

• The property is in a conservation area (rules vary by council)

• PD rights have already been removed or used

Each council interprets rules slightly differently, which is why drawings matter.

Do I still need drawings if no planning permission is required?

Yes — almost always.

Even if your extension is permitted development, you’ll typically need:

• Scaled architectural drawings

• Plans suitable for building control

• Drawings for builders to price accurately

Many homeowners also apply for a Lawful Development Certificate to confirm the extension is legal — this requires professional plans.

Can I submit planning drawings myself?

Technically, yes.

Practically, it often causes problems.

Common issues with DIY submissions include:

• Incorrect scaling

• Missing drawings

• Non-compliant layouts

• Council requests for amendments

Professionally prepared drawings greatly improve approval chances and reduce back-and-forth with planners.

How long does planning approval take?

Typical timescales:

• Permitted development / lawful certificate: 6–8 weeks

• Full planning application: 8–10 weeks

Delays are common if drawings are unclear or incomplete.

Should I speak to an architectural designer?

If you want certainty, good design, and fewer delays — yes.

A designer can:

• Confirm whether permission is required

• Design to maximise PD allowances

• Prepare planning-ready drawings

• Advise on building regulations

This often saves money overall by avoiding redesigns and re-submissions.

Need help with rear extension drawings?

If you’re considering a rear extension and want to know:

• Whether planning permission is required

• What size extension is realistic

• What drawings your council will expect

I can review your proposal and prepare clear, council-ready drawings.

👉 Get in touch for advice or a quote.