Do You Need Planning Permission? How to Know When Planning Permission is Required

Understanding what planning permission means

Planning permission is the formal approval you need from your local authority to carry out building works or make major changes to your property. It ensures your project fits with local development plans, doesn’t harm neighbours’ amenities, and meets national design and environmental standards.

In most cases, you’ll need planning permission for major structural changes, new dwellings, or anything that alters the external appearance significantly — especially in conservation or listed areas.

When planning permission is required

You’ll typically need permission if your project:

• Creates a new building or separate dwelling (for example, a new house or annex).
• Extends beyond the limits allowed under house extension permitted development rules.
• Changes the use of a building (for instance, converting a shop into a flat).
• Raises the height of a roof, adds multiple storeys, or significantly changes external materials.
• Is located within a conservation area or involves a listed building.

If your proposal doesn’t fall under these categories, it may be allowed under permitted development — but you should still confirm before starting work.

When work can be done under permitted development

Permitted Development (PD) rights allow homeowners to carry out minor works without full planning permission, provided strict limits are met. These rights apply to many types of improvement, such as small extensions, loft conversions, and certain outbuildings.

Examples of common PD-eligible works include:

• Loft conversions under 40–50m² (depending on property type).
• Porches under 3m² in floor area and under 3m high.
• Rear extensions that do not extend more than 3m (terraced/semi) or 4m (detached) from the rear wall.
• Garden rooms not used as self-contained accommodation.

Common triggers that require permission

Even projects that look minor can fall outside PD limits. The most frequent triggers for when planning permission is required include:

• Extensions that take up more than 50% of the original garden area.
• Any extension facing a highway or principal elevation.
• Raising the roof ridge or installing dormer windows on the front elevation.
• External materials that don’t match the existing property.
• Outbuildings or garages used as separate accommodation.

Local council and area-specific restrictions

Each local planning authority interprets national guidance slightly differently. This means that two identical extensions may be treated differently depending on where you live. Councils can also introduce Article 4 Directions that remove permitted development rights for certain neighbourhoods or building types.

Examples include:

• Planning Permission High Wycombe – strict height and materials rules in Article 4 zones.
• Planning Permission Buckinghamshire – differing rural vs. urban PD limits.
• Planning Permission Guildford – additional constraints on ridge heights and extensions in conservation belts.

How to confirm if you need planning permission

Step 1 – Review national guidance

Start with the Planning Portal, which provides official criteria for England and Wales. Look up your project type and compare measurements against PD limits.

Step 2 – Check your property’s planning history

Use your local authority’s online planning register to see if previous extensions already used up PD allowances or had special conditions attached.

Step 3 – Request a pre-application enquiry

Many councils offer pre-application advice. This informal feedback can clarify if permission is likely to be required or approved — a worthwhile early step.

Step 4 – Get professional drawings

Accurate planning permission drawings make it easier for the council to understand your proposal and assess compliance. Our team prepares drawings ready for submission to local planning authorities.

Step 5 – Apply (if required)

If planning permission is needed, submit your application through the Planning Portal or directly to your council. Include all required documents, design statements, and site plans.

Step 6 – Await a decision

Most councils aim to decide within eight weeks, though larger or more complex projects can take longer. You’ll receive an approval notice or refusal letter with reasons and options to appeal if necessary.

Frequently asked questions

Next steps & useful guides

• Do I Need Planning Permission?
• Building Regulations: Complete Homeowner’s Guide
• Planning Permission Timelines
• Planning Permission Appeal
• Planning Permission Cost (UK Guide)

Key facts snapshot

For official guidance, visit the Planning Portal or GOV.UK planning pages.