How long does a building permit last before it expires?

Building permit validity varies by jurisdiction, but a common pattern in the US and Canada is 12-24 months from the date of issue, or 6-12 months from the date work must begin (sometimes both conditions apply simultaneously). In the UK, planning permission typically lapses if work hasn't commenced within 3 years of approval; building regulations approval works on a different clock with a shorter commencement window.

Most jurisdictions allow extensions, but they must be requested before the permit expires -- not after. An expired permit that hasn't been extended requires a new application, which means new fees, new review, and potentially new compliance with updated codes. Inspections already completed under the expired permit may not count. Work done on an expired permit can require demolition to be re-inspected from the start. Checking the exact expiry conditions in the permit documents themselves is essential -- they vary even within a single city.