Do I need planning permission for my extension or renovation?

Plenty of home projects in England and Wales are built without a planning application, under permitted development rights. Plenty of others are refused because the owner assumed they were covered. This guide helps you work out which side you are on before you spend money on drawings.

The three routes

1. Permitted development (PD): no planning application needed, provided the work stays inside strict limits. Strongly worth applying for a Lawful Development Certificate anyway — it is your proof at sale.
2. Householder planning application: needed when you exceed PD limits, or when PD does not apply to your property.
3. Full planning / additional consents: needed for flats, new dwellings, changes of use, and anything affecting a listed building.

When permitted development usually covers you

Broadly, and subject to the current General Permitted Development Order:

• Single-storey rear extension up to 3m deep on a terraced or semi-detached house, or 4m on a detached house (larger under the prior-approval neighbour consultation scheme).
• Maximum height 4m for a single-storey rear extension, and eaves no higher than the existing eaves within 2m of a boundary.
• Side extensions no wider than half the width of the original house, single storey only.
• Loft conversions within a volume allowance (commonly 40 m3 for terraces, 50 m3 for semis and detached), with no dormer on the principal elevation facing a highway.
• Outbuildings and garden rooms, if single storey, incidental to the house, and within height limits.

"Original house" means as built, or as it stood in 1948. Previous owners' extensions eat into your allowance.

When PD does not apply

• Flats and maisonettes — always need permission.
• Listed buildings — listed building consent is required, and it is a criminal offence to proceed without it.
• Conservation areas, National Parks, AONBs and World Heritage Sites — side extensions, cladding and some rooflights lose PD rights.
• Properties where an Article 4 Direction has removed PD rights. Many London boroughs use these.
• New-build estates with planning conditions removing PD.

Check your title deeds too. Restrictive covenants are a private legal matter, not planning, but they can still stop the work.

Planning is not building regulations

They are separate. Planning controls what the outside looks like and its impact on neighbours. Building regulations control structure, insulation, fire safety, drainage and ventilation. Almost every extension needs building control approval even when planning permission is not required.

How long it takes

• Lawful Development Certificate: usually 8 weeks.
• Householder planning application: statutory 8 weeks, often longer if the case officer requests changes.
• Prior approval for a larger rear extension: 42 days, including a 21-day neighbour consultation.
• Listed building consent: 8 weeks, frequently longer, and pre-application advice is worth paying for.

Build these into your programme before agreeing a start date with a contractor.

What improves your chances

• Read your council's householder design guide and follow it.
• Pay for pre-application advice on anything unusual, or in a conservation area.
• Talk to neighbours before you submit, not after they receive the consultation letter.
• Respect the 45-degree daylight rule and avoid overlooking habitable rooms.
• Match materials, or contrast confidently and deliberately — half-hearted matching is what gets refused.

If you are refused

You can amend and resubmit — usually free within 12 months — or appeal to the Planning Inspectorate, which takes months. Amending is nearly always faster.

Next step

BuildWise Workspace builds the planning route into your programme, so the approval you actually need appears on your timeline with realistic durations, and you can appoint the right designer for that route from a network of over 1,000 UK practices.