Survey finding
Extension without planning consent: what to do
Extensions built without planning permission are common on older UK housing. This page covers the enforcement clock, Certificate of Lawfulness, and indemnity insurance.
Last updated: 6 May 2026. Editorially reviewed: 20 May 2026.
Finding
Extension without planning consent
What this usually means
An extension built without planning permission can be either: (a) under permitted development rights (PD) and so didn't need permission; (b) needed permission and went ahead without it; or (c) built before 1948 when planning didn't apply. Local authority enforcement is time-limited, generally 4 years for unauthorised building works (extending to 10 years under the Levelling Up and Regeneration Act 2023 in some cases), after which a Certificate of Lawfulness can be obtained.
Why it matters
Lenders typically require evidence of planning compliance, either the original consent, evidence the works were under PD, or a Certificate of Lawfulness. Indemnity insurance is the common fallback where evidence is absent. The 4-year/10-year enforcement clock matters: if the extension is recent, indemnity may not be available.
Ask your surveyor
- Check:Does the extension look professionally built and does it match the original property?
- Check:Are there visible signs of structural issues or non-compliance with current Building Regs?
Ask the seller
- Check:Was planning permission obtained for the extension?
- Check:Is there a Building Regulations completion certificate?
Next steps
- •Get two written quotes from local trades before negotiating with the seller.
- •Speak to your mortgage broker before exchanging if the finding affects mortgageability.
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What you need to know
Severity
Significant. Specialist follow-up usually warranted before exchange.
Typical cost to fix
Certificate of Lawfulness application: £206 (England) plus drawings and supporting evidence £500–£1,500. Retrospective planning application £206–£500 plus design fees. Indemnity insurance £150–£600 one-off where time-barred.
Mortgage impact
Most mainstream lenders accept retrospective consent or Certificate of Lawfulness. Indemnity insurance is widely accepted where the extension is time-barred from enforcement. Lenders are more cautious where the extension is recent or where Building Regulations approval is also missing.
Insurance impact
Indemnity insurance covers enforcement risk where the extension is time-barred but unauthorised.
When to pull out
Pull out if a recent unauthorised extension cannot be regularised, indemnity is unavailable, and the lender refuses.
When to renegotiate, and by how much
Ask the seller to obtain Certificate of Lawfulness or fund indemnity insurance. Not typically a price-renegotiation item unless the works are also defective.
Thinking of pulling out or renegotiating? What to do after a bad survey
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No planning permission for extension , often sits near extension without planning consent on a survey and is the next thing to check.
How MyPropertyScan produces this guide, and what it is not
Published by MyPropertyScan and written by Ziad Nasr, who is accountable for its accuracy. No page here is written or reviewed by a chartered surveyor, conveyancer or regulated adviser, and we do not claim otherwise.
This page is not:
- Chartered surveying — we do not inspect properties or produce RICS Home Survey reports
- Legal advice — we do not act as conveyancers or advise on title, tenure or contracts
- Mortgage or insurance advice — we are not regulated by the FCA and give no recommendations
Figures and process steps come from the published UK datasets and standards listed on this page, not from professional practice. Pages are updated when source coverage, survey cost assumptions, or lender and legal requirements materially change. Dataset limitations are set out on the methodology page.
Spotted something out of date or wrong? Email hello@mypropertyscan.com and we will correct it and change the update date.
Sources used
We use UK public and specialist sources where they are available. Public datasets can be incomplete, delayed, or missing for some addresses. Treat them as a starting point, not as a replacement for professional advice.
Source standard: preference goes to official government datasets, statutory bodies, professional standards, and primary dataset publishers. We cite the source family on the page and explain coverage limits rather than filling gaps with unsupported estimates.
- Professional standard: RICS Home Survey StandardRICS standard for condition-based residential surveys in the UK.
- Learn more from: RICS consumer guide to surveysConsumer-facing guide to survey types and when each level is appropriate.
- Official guidance: GOV.UK buying or selling your homeGovernment overview of the home buying and selling process.