Permitted development & Article 4 checker — do I need planning permission?

Check your planning route

Answer a few questions about your home and your plans. No email or sign-up — your verdict shows straight away.

Check by extension type

• Single-storey rear extension

  Often permitted development within depth and height limits.

• Two-storey rear extension

  Tight rules on boundary distance; often full planning in London.

• Side extension

  Half the original width, single storey — and never on designated land.

• Wraparound extension

  A combined side + rear assessment — usually full planning.

• Rooflight (Velux) loft conversion

  Usually permitted development off designated land.

• Dormer loft conversion

  Volume limits apply; not permitted on designated land.

• Hip-to-gable loft conversion

  Class B volume limits; needs a hipped roof to start with.

• Mansard loft conversion

  Almost always full planning permission.

• Additional storey (upward extension)

  Class AA prior approval — strict age and height limits.

• Porch

  Small porches are permitted development (Class D).

• Outbuilding / garden room

  Curtilage and height limits under Class E.

• Garage conversion

  Usually permitted development — unless a condition removed PD.

Frequently asked questions

What’s the difference between planning permission and building regulations?

They are two separate approvals. Planning permission controls whether you can build and how it looks and affects neighbours; building regulations control how it is built — structure, fire safety, insulation, drainage and ventilation. A project can be permitted development, needing no planning application, yet still need building-regulations approval. Most extensions and conversions must satisfy both.

What is a Lawful Development Certificate and do I need one?

A Lawful Development Certificate (LDC) is a formal council document confirming that your work is lawful permitted development. It is not a planning permission — it proves you did not need one. It is optional but strongly recommended: it is the evidence buyers, solicitors and lenders ask for when you sell. The checker links you to your council’s portal.

What is an Article 4 direction?

An Article 4 direction is made by a council to remove specified permitted-development rights in a defined area — often a conservation area or particular streets. Where one applies, work that would normally be permitted development instead needs a full planning application. In London these directions are zone or street-specific, so the checker names the exact one at your address.

How much of my garden can I cover with an extension?

Under permitted development, all extensions and outbuildings together must not cover more than half — 50% — of the area of land around the "original house" (as it stood in 1948, or as first built). Exceeding this 50% rule tips the whole scheme into needing full planning permission, even if every other limit is met.

What happens if I build without planning permission?

Unauthorised building is not automatically safe after a fixed period. Since 25 April 2024 England has a single 10-year enforcement time limit for most breaches (Levelling-up and Regeneration Act 2023, section 115, amending the Town and Country Planning Act 1990); the older four-year rule no longer applies in England, though Wales retains it. The safe route is a Lawful Development Certificate.

Can my neighbour stop my extension?

Neighbours cannot block genuine permitted development, because no planning application is involved. For a full planning application they can comment and object, and the council weighs material planning considerations, but personal objections alone do not decide it. Separately, the Party Wall etc. Act 1996 gives neighbours rights over shared-boundary works — a different process from planning.

Does this checker cover the whole UK?

It covers England only. The General Permitted Development Order is an England instrument, and permitted-development rules differ in Scotland, Wales and Northern Ireland. If you enter a non-England postcode, the checker tells you rather than giving a verdict that would not apply.