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Free 2026 London Planning Report — London planning glossary

London rooftops and rear gardens across several boroughs, the housing stock these planning terms govern
Planning Glossary

The London Planning Terms That Decide Your Extension

Eight terms do most of the damage on a London householder project. Each one gets a straight definition, the statute it comes from, and the real London numbers behind it.

Most planning confusion is vocabulary. “Permitted development” sounds like permission and is not; “prior approval” sounds like a formality and is frequently refused; a conservation area and an Article 4 direction get used interchangeably and are different instruments with different consequences. Each page below defines one term, cites the legislation it comes from, and shows what actually happens across the 33 London boroughs — from government data, not estimates.

Article 4 directionAn Article 4 direction removes permitted development rights in a defined area. Work that would need no application elsewhere — a rear extension, new windows, a front boundary wall — needs full planning permission inside one. Councils use them to protect the character of conservation areas and terraced streets.Permitted developmentPermitted development is planning permission granted nationally by legislation rather than by your council. If a project stays inside every published limit — depth, height, materials, position — it needs no planning application. Exceed one limit, or sit under an Article 4 direction, and it does.Lawful development certificateA lawful development certificate is a council's formal decision that works are lawful without planning permission — either because they are permitted development, or because they have stood long enough to be immune from enforcement. It is decided on fact and dimension, not on design merit.Conservation areaA conservation area is an area designated by the council for its special architectural or historic interest. Designation does not freeze it, but it removes some permitted development rights, adds control over demolition and trees, and raises the bar on design in any application.Prior approvalPrior approval is a narrow council check on named aspects of a project that is otherwise permitted development — usually impact on neighbouring amenity, transport or flooding. The council cannot refuse on grounds outside that list, but within it, refusal is common.Party Wall etc. Act 1996The Party Wall etc. Act 1996 governs work to a shared wall, building on the boundary line, or excavating near a neighbour's foundations. You must serve written notice — two months for party wall work, one for excavation — whether or not you need planning permission.Building regulations approvalBuilding regulations approval confirms that work meets national construction standards for structure, fire safety, insulation, ventilation and drainage. It is separate from planning permission: planning asks whether the building may exist in that form, building control asks whether it is safe to occupy.Planning appealA planning appeal asks the Planning Inspectorate, an independent national body, to redetermine your council's refusal. For householder applications the deadline is twelve weeks from the decision, and the appeal is decided by an inspector on the planning merits.
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