How Long Does Planning Permission Last?
Planning permission in England does not last indefinitely. Once your permission is granted, there is a defined window within which you must commence the approved development — and if that window passes without work starting, the permission expires. Here's what the rules are, and what to do if your permission is approaching its time limit.
The Standard Time Limit
Under the Town and Country Planning Act 1990 (as amended), full planning permission must be implemented within three years of the date of the decision notice, unless the planning authority has specified a different period as a planning condition. The majority of householder planning permissions specify a three-year implementation period.
"Implementation" means physically starting the approved development on site — not completing it. Once you have lawfully started the development within the three-year period, the planning permission remains valid for the entirety of the works even if they continue beyond that period.
Prior Approval for Larger Home Extensions
Prior approval for a Larger Home Extension (the prior approval route for single-storey rear extensions beyond standard PD limits) must be commenced within three years of the prior approval being granted. The same three-year rule applies.
What Counts as "Commencing Development"?
This is a technical legal point and has been the subject of case law. In general, development is considered to have commenced when a material operation is carried out — typically defined as any operation that is part of the approved development and is not merely preparatory. In practice, for a home extension or loft conversion, this means the contractor must be on site doing actual construction work, not just clearing vegetation or erecting a site sign.
To be certain of having commenced development before a permission expires, it's advisable to undertake a meaningful physical operation (such as excavating foundations, laying the first course of blockwork, or cutting into the roof structure) and to inform the local planning authority that development has commenced.
If Your Permission Is About to Expire
If your three-year window is approaching and you are not yet ready to start, you have two options:
Submit a fresh planning application. If the scheme is unchanged and planning policy hasn't significantly altered, a fresh application is likely to be granted — but it involves re-running the application process, incurring fees, and waiting for a decision.
Commence development minimally before expiry. As noted above, starting a meaningful physical operation preserves the permission. This is a legitimate approach, but you should take legal advice on what constitutes valid commencement in your specific case before relying on it.
Change of Ownership
Planning permission runs with the land, not the applicant. If you sell the property after planning permission has been granted but before development begins, the new owner can implement the permission in the same way you could — subject to the same time limits.
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