Two genuinely different legal routes exist for regularising a conservatory built without permission — and a recent law change has extended how long enforcement action can be time-barred.

This article covers regularising an unauthorised conservatory or extension in England. It is general information, not planning advice for your specific situation – if you’re dealing with this directly, a planning consultant or solicitor experienced in enforcement matters is worth the cost.

Why this situation comes up

It’s a more common problem than people expect: a conservatory that turns out to exceed permitted development limits, was built without the planning permission it actually needed, or was put up by a previous owner without proper consent. Sometimes it only surfaces when you come to sell, and a buyer’s conveyancer or lender flags a mismatch between what’s on the ground and what the planning records show.

Option one: apply for retrospective planning permission

English planning law specifically allows you to apply for planning permission for development that’s already been carried out – this is a genuine, legitimate route, not a loophole. The council has to assess a retrospective application on exactly the same planning merits as it would have assessed the same proposal before you built it; it cannot refuse simply because the work is already done, though in practice the fact that it exists doesn’t guarantee approval either. If the retrospective application is refused, the council can then take enforcement action requiring alteration or removal – so this route carries genuine risk if the structure wouldn’t have been approved in the first place, and it’s worth an honest planning assessment before applying, rather than applying and hoping.

Option two: a Certificate of Lawfulness, but only once enough time has passed

This is a different legal route entirely, and it’s commonly confused with retrospective permission. A Certificate of Lawfulness of Existing Use or Development doesn’t ask the council to judge the planning merits of the structure at all – it’s a factual and legal determination confirming that the council can no longer take enforcement action because the relevant time limit has passed. To succeed, you generally need to provide solid evidence – dated photographs, utility bills, statutory declarations from neighbours, or similar – proving the structure has existed continuously, without a break, for the full relevant period. If you can’t demonstrate that continuity, or the time limit hasn’t actually passed yet, this route isn’t available to you, and retrospective planning permission is your only option.

The enforcement time limit itself has recently changed

This is a genuinely important point to check carefully rather than assume. Historically, most unauthorised building work in England became immune from enforcement action after four years. Changes introduced through the Levelling Up and Regeneration Act 2023 have extended this time limit to ten years for most types of unauthorised development, bringing building work into line with the longer period that already applied to unauthorised changes of use. Transitional rules govern exactly how this applies depending on when the unauthorised work took place, so don’t assume an older four-year rule of thumb still protects work carried out some years ago – check the current position, including any transitional provisions that might apply to your specific dates, with your council or a planning professional before relying on any time limit.

What happens if you do nothing

Leaving an unauthorised structure unresolved doesn’t make the underlying problem go away, even once enforcement action is technically time-barred, because without a formal Certificate of Lawfulness, there’s no official record confirming that status. This routinely surfaces at the worst possible time – during a sale, when a buyer’s solicitor or mortgage lender wants clarity and isn’t willing to simply take your word for it.

Indemnity insurance: a workaround, not a fix

In some cases, particularly where enforcement risk is genuinely low but no formal certificate has been obtained, conveyancers sometimes suggest indemnity insurance as a way to satisfy a buyer or lender rather than formally regularising the structure. This can work in the right circumstances, but it’s a commercial workaround rather than a legal resolution – it doesn’t make the structure lawful, it simply insures against the financial consequences if enforcement action is ever taken, and not every lender or buyer will accept it as sufficient. Getting proper retrospective permission or a Certificate of Lawfulness, where either is genuinely available to you, resolves the underlying issue rather than just insuring around it.

Practical first steps

• Establish exactly what was built, when, and what (if any) permission was obtained at the time;
• Gather any dated evidence you have of the structure’s history, in case a Certificate of Lawfulness becomes relevant;
• Get an honest, early assessment of whether the structure would likely pass on its planning merits before applying for retrospective permission;
• Don’t wait until you’re trying to sell to address it – resolving it in advance avoids a rushed, pressured process during a transaction.

FAQs

What’s the difference between retrospective planning permission and a Certificate of Lawfulness?

Retrospective planning permission asks the council to judge the structure on its planning merits, with a real risk of refusal and enforcement action if it wouldn’t have been approved. A Certificate of Lawfulness doesn’t judge the merits at all – it’s a factual and legal determination that enforcement action is now time-barred, and it’s only available once you can prove the structure has existed continuously for the full relevant period.

How long does an unauthorised conservatory need to stand before it becomes immune from enforcement?

Historically this was four years for most unauthorised building work in England. Changes introduced through the Levelling Up and Regeneration Act 2023 extended this to ten years for most types of unauthorised development, with transitional rules governing exactly how it applies depending on when the work took place.

Sources

This guide draws on the following primary sources, current as of 15 September 2026:

• Planning Portal, retrospective planning permission – planningportal.co.uk
• GOV.UK, planning enforcement guidance – gov.uk/guidance/ensuring-effective-enforcement
• Legislation.gov.uk, Levelling-up and Regeneration Act 2023 – legislation.gov.uk
• Legislation.gov.uk, Town and Country Planning Act 1990 – legislation.gov.uk

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