If you’ve secured planning permission for a home extension, loft conversion or even a new build, you might be asking yourself: How long does planning permission last?
Building projects often take longer than expected, and with deadlines set by the council, it’s important to know how much time you really have — and what to do if your permission is about to expire.
In this guide, we’ll explain how long planning permission lasts, what counts as starting work, whether it can be extended, and what to do if your approval has already expired.
How long does planning permission last in the UK?
In most cases, planning permission lasts for three years from the date your local authority approves it.
- Full planning permission – You must start building work within three years.
- Outline planning permission – You have three years to apply for the detailed “reserved matters.” Once those are approved, you then have two further years to begin construction.
Unless your decision notice says otherwise, the three-year rule applies to most home projects.
What counts as starting work?
You don’t need to finish your project within three years, but you do need to make a genuine start before your permission expires.
Examples of accepted works include:
- Digging the foundations
- Demolishing existing structures
- Laying underground services (pipes, drains, cables)
- Starting an access road or driveway
Important: You must discharge any pre-commencement planning conditions first. For example, if your council requires details of materials or landscaping, these must be signed off before you can begin digging trenches or demolishing walls. Otherwise, the work may not legally count.
If your project is liable for a Community Infrastructure Levy (CIL), payment must also be made before work officially starts. Where an exemption has been granted (such as for a self-build home), you must notify the council of commencement using the correct form, otherwise the exemption may be lost.
To avoid any doubt later on, it’s also sensible to have an official record that work has begun. Submitting a Building Regulations application means the start date will appear on the council’s system. Some homeowners also choose to apply for a Lawful Development Certificate, which provides written confirmation from the Planning Department that the permission has been lawfully implemented.
Can planning permission be extended?
A common question homeowners ask is: Can I extend my planning permission?
Unfortunately, since 2013, it is no longer possible to simply “renew” an approval. If your permission is nearing expiry, you have two main choices:
- Start meaningful work before the deadline – even small but genuine works may be enough to keep it valid.
- Submit a new application – this will be judged against current planning policies, which may have changed since your original approval.
In some cases, you may also be able to reapply under Section 73 of the Town and Country Planning Act, which allows you to vary conditions. However, this is not the same as an extension, and it still requires a fresh decision from the council.
It’s also worth noting that Permitted Development rights (such as certain extensions or loft conversions) do not carry a three-year expiry date. If you’ve applied for a Lawful Development Certificate to confirm your project qualifies as Permitted Development, the certificate itself remains valid indefinitely, as long as the proposal is unchanged.
What if planning permission expires?
If planning permission lapses before work begins, you’ll need to reapply in full.
While previous approval can sometimes help set a precedent, there are no guarantees. Councils regularly update their planning policies, so an application that was acceptable three years ago may now be refused.
For homeowners making modest improvements, such as a rear extension or loft conversion, the risk is lower than for large developments. Still, it’s worth checking the latest planning rules before resubmitting.
Why professional help matters
Understanding how long planning permission lasts is only one part of the process. Getting the timing and conditions right can make the difference between a smooth build and a frustrating setback.
Working with an architect ensures you:
- Know exactly when your permission will expire
- Correctly discharge all planning conditions
- Deal properly with CIL payments or exemptions
- Have clear proof that your planning has been lawfully implemented
- Get advice on whether to begin works or reapply
- Have drawings and applications that meet the latest standards
At AML Architects, we specialise in helping homeowners across South London make the most of their property — from extensions and loft conversions to one-off houses.
Whether you’re looking for an architect in Chislehurst for a family home extension, an architect in Surbiton for a loft conversion, or an architect in Wimbledon for a complete remodel, our team can guide you through planning permission and beyond.
We also offer a free initial consultation, so you can discuss your project and get clear, practical advice before committing.
FAQs: How Long Does Planning Permission Last?
1. What happens if planning permission expires before work starts?
If planning permission expires, you must submit a new application. The new application will be assessed under current planning policies, which may have changed since your original approval.
2. How can I prove I’ve started work before my permission runs out?
Carrying out meaningful works like digging foundations counts, but it’s best to keep official proof. Submitting a Building Regulations application or applying for a Lawful Development Certificate ensures the start is formally recorded.
3. Does planning permission ever last longer than three years?
Only in rare cases. For example, outline planning permission has slightly different rules (three years to apply for details, then two years to start). Most household projects must begin within three years.
4. Do Permitted Development rights expire?
No, Permitted Development rights don’t have an expiry date. However, if you applied for a Lawful Development Certificate to confirm your project, the certificate remains valid indefinitely as long as the proposal itself doesn’t change.