If you have just had a project approved, you are probably asking how long does planning permission last before you need to start building. It is a fair question. the answer is Three Years for Most Projects.
Most homeowners find this out the hard way. They wait too long, then have to reapply from scratch.
How Long Does Planning Permission Last? Three Years for Most Projects
For the vast majority of homeowners in England, full planning permission lasts three years from the date on your decision notice. This applies to house extensions, loft conversions, kitchen extensions, and most home renovation projects. The clock starts on the day your local council approves the application, not the day you actually pick up a tool.
This three-year limit has been standard since 2009. Before that, councils set their own time limits, often five years. Today, unless your decision notice says otherwise, three years is the rule under the Town and Country Planning Act 1990.
Why Three Years, and Not Something Else?
Planning policy changes over time. Local plans get updated. Road layouts shift. A local planning authority wants to make sure that what gets built still fits current rules, not rules from years ago. Three years is seen as a fair balance between giving homeowners time to organise finances and builders, while stopping old approvals from sitting around indefinitely.
How Long Does Outline Planning Permission Last?
How long does outline planning permission last is a separate question, and the answer works differently. Outline permission only approves the principle of development, not the fine detail. Because of that, it comes with two separate deadlines instead of one.
First, you have three years to submit what is called a reserved matters application. This covers details left out of the outline stage, such as design, layout, access, and landscaping. Once reserved matters are approved, you then get a further two years to begin construction.
- Stage one: submit reserved matters within 3 years of outline approval
- Stage two: start work within 2 years of reserved matters approval
- Total possible window: up to 5 years from the original outline decision
Miss either deadline and the whole outline permission lapses. There is no grace period and no automatic warning letter from the council.
How Long Does Planning Consent Last for Larger Sites?
For bigger or phased developments, a council can set a different planning permission time limit under section 92 of the Act. Large sites sometimes get much longer windows, occasionally a decade or more for later phases. This is unusual for a typical house extension, but worth checking if your project sits within a larger site allocation.
What Actually Counts as Starting Work?
This trips up a lot of homeowners. Simply having materials delivered to the site is not enough. To legally start development, you need what planners call a “material commencement.” This generally means genuine, meaningful building work has begun.
Examples that usually count:
- Digging foundation trenches
- Laying the first course of brickwork
- Demolition work connected to the approved scheme
- Certain groundworks tied directly to the project
Examples that usually do not count:
- Ordering bricks or windows
- Storing scaffolding on site
- A site visit from your builder
If you are close to your planning permission expiry date, speak to your local council before assuming a small task is enough to keep your approval alive.
How Long Does a Planning Permit Last Once Work Has Started?
Once genuine construction has started, the picture changes. How long does a planning permit last after that first spade goes in the ground? In most cases, once work has properly begun, your permission remains valid indefinitely, even if the build takes several years to finish. There is no need to complete the whole extension within the original three-year window.
There is one exception. If a council issues a completion notice, you must finish the project within twelve months of that notice. This is rare for standard home extensions and tends to apply to larger or stalled sites.
What Happens If Your Planning Permission Expires?
If you miss the deadline, your approved planning application simply becomes invalid. You cannot start work under it anymore. The only route forward is submitting a brand new application.
The good news is that renewing is usually simpler than starting from zero. If policies have not changed much since your original approval, a fresh application covering the same scheme is often approved quickly. If local rules have shifted, for example new rules on extension sizes or conservation area restrictions, you may need to adjust your plans.
Costs and Delays to Expect
- A new application fee, similar to your original one
- A typical wait of 8 to 10 weeks for a decision
- Possible new conditions if planning policy has changed
- A need to update drawings if building regulations have moved on
Budgeting extra time here matters. How long do planning applications last while waiting for a decision varies by council workload, so build in a buffer before you plan to start building.
Can You Extend or Renew Planning Permission?
There is no formal way to simply extend an existing consent past its expiry date. What you can do is apply for a new permission covering an identical or nearly identical scheme, sometimes called a renewal application. This does not restart your original clock. It creates a brand new three-year window from the date of the new approval.
If your circumstances have changed, for example you now want a bigger kitchen extension or an extra bedroom, this is also the point to update your drawings rather than trying to squeeze changes into an expired approval.
How Long Is a Planning Permission Valid For If You Bought a Property With Existing Approval?
Buying a house with an unused planning permission attached is common in London and the surrounding areas. How long is a planning permission valid for in this situation depends entirely on the date it was originally granted, not the date you bought the property. Always check the decision notice date on your council’s planning portal before assuming you have the full three years left.
How to Check Your Planning Permission Validity Period
- Search your address or application reference on your council’s online planning register
- Look for the decision notice and note the exact grant date
- Check for any special conditions that alter the standard time limit
- Confirm whether your approval is full, outline, or reserved matters
Common Mistakes Homeowners Make With Planning Permission Duration UK Rules
Getting the planning permission duration UK rules wrong is more common than people think. Some frequent mistakes include:
- Assuming the clock starts when building work begins, not when permission was granted
- Believing that ordering materials counts as starting work
- Forgetting outline permission has two separate deadlines, not one
- Not checking conditions that shorten the standard three-year period
- Leaving a renewal application too late to avoid a construction gap
Why Work With ABL Design & Build
Timing matters just as much as design when it comes to home improvement projects. At ABL Design & Build, we help homeowners track planning deadlines, prepare accurate drawings, and avoid the costly trap of a lapsed approval. Whether you are planning house extensions London homeowners have trusted us for, a loft conversion, or a full renovation, we manage the planning process alongside the build itself, so nothing slips through the gaps.
Final Thoughts
Planning permission does not last forever, and missing a deadline can cost you time and money. Know your dates, understand the difference between full and outline consent, and start work properly within your window. If you are unsure where your project stands, we can review your approval and help you plan the next steps. Contact us today for a free consultation and keep your project on track before your permission runs out.