The standard 3-year window
Section 91 of the Town and Country Planning Act 1990 sets the default duration of a full planning permission in England at 3 years from the date of the decision notice. The decision notice will state the exact expiry date. Some applications carry a shorter or longer window if a condition specifies — read condition 1 of every decision notice carefully as it almost always sets out the time limit. Outline permissions work differently: the outline approval gives you 3 years to apply for reserved matters (or whatever the condition specifies), and then a further 2 years from reserved matters approval to commence development. Listed Building Consent has its own 3-year clock that runs in parallel — both must be implemented before expiry, not just one.
What counts as a material start
A 'material start' is any substantive, lawful work referenced in the planning consent. Pouring oversite concrete, digging foundation trenches, or removing a load-bearing wall covered by the consent will all typically count. Token works do not — putting up a fence, demarking the site or temporary digging without commitment is unlikely to count. Crucially, all pre-commencement conditions must be discharged before the material start, otherwise the works are unlawful and the permission can lapse. Common pre-commencement conditions in London include: tree protection plans, construction management plans, sustainable drainage details, materials samples, and arboricultural method statements. Discharge each condition via the formal condition discharge application (typically £116 fee) and obtain written confirmation before breaking ground.
Keeping permission alive and the consequences of lapse
Once a permission has been lawfully implemented (material start made, all pre-commencement conditions discharged), it remains valid indefinitely — there is no longer a deadline to finish the works. This is why planning consultants advise clients to make a defensible material start within the 3-year window even if the main works will not begin for several months. If the permission lapses, a fresh application is required at full fee with no guarantee of approval — planning policy, neighbour objections and officer turnover can all change in three years. London councils enforce expiry strictly and will not extend by negotiation. Re-applications also re-trigger CIL liability and any Section 106 obligations attached to the original consent.
