What is the difference between planning permission and building regulations?
Planning permission governs whether you may build something — its size, appearance and impact on neighbours. Building regulations govern how it must be built — structure, fire safety, insulation, drainage and ventilation. They are separate approvals and you frequently need both.
Planning is about the effect on other people and on the area: how big the extension is, what it looks like, whether it overshadows a neighbour, whether it suits a conservation area. It is administered by the council's planning department and decided against local and national policy. A project can fall under permitted development and need no planning application at all.
Building regulations are about safety and performance, and they apply to almost all building work regardless of whether planning permission is needed. They cover structural adequacy, fire escape, thermal insulation, ventilation, drainage, electrical safety and sound insulation. There is no permitted development equivalent — an inspector must approve the work, and the process ends with a completion certificate.
The practical consequence is that a project can be entirely lawful in planning terms and still be unlawful in building control terms. A loft conversion built under permitted development with no fire doors and a non-compliant staircase needed no planning permission and is still unlawful. The completion certificate is the document that matters when you sell, and it is the one people most often find is missing.
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