What Happens If You Build Without Planning Permission?

Building without planning permission (when you need it) is called “unauthorised development.” It is a breach of planning control, not a crime. Your council cannot fine you or prosecute you just for building without permission.

However, your council can take enforcement action to make you put things right. And the consequences when selling or remortgaging can be significant.

Enforcement notices

If your council decides that the unauthorised development is harmful — for example, it harms the appearance of the area, affects neighbours, or breaches planning policy — it can issue an enforcement notice. This is a formal legal notice that requires you to:

• Remove the unauthorised development entirely, or
• Alter it to make it acceptable, or
• Apply for retrospective planning permission

An enforcement notice gives you a deadline to comply (usually at least 28 days, often longer). If you do not comply, the council can prosecute you — and non-compliance with an enforcement notice is a criminal offence.

Breach of condition notices

If you have planning permission but have not complied with one of its conditions, your council can issue a breach of condition notice. This requires you to comply with the condition within a set period. There is no right of appeal against a breach of condition notice.

Stop notices

In urgent cases, your council can issue a stop notice requiring you to stop work immediately. This is rare and typically used for large-scale or commercially harmful unauthorised development, not routine householder cases.

Injunctions

In extreme cases, your council can apply to the court for an injunction to stop or remove unauthorised development. Again, this is rare for householder projects.

Your council cannot take enforcement action forever. There are statutory time limits:

• 4 years for building work (extensions, outbuildings, loft conversions, structural alterations)
• 10 years for changes of use (converting a house into flats, or a residential property into a business)
• 10 years for breach of a planning condition

If more than 4 years have passed since building work was completed and the council has not issued an enforcement notice, the development becomes lawful through the passage of time. You can apply for an existing Lawful Development Certificate (Section 191) to confirm this.

Important: The 4-year rule applies from the date the work was substantially completed, not from the date it started. And if the development was deliberately concealed, the time limits may be extended.

This is where most homeowners discover the problem. When you sell a property, the buyer’s solicitor will check:

• Whether any building work has been carried out
• Whether it had planning permission or was permitted development
• Whether building regulations approval was obtained and a completion certificate issued

If there is no evidence that the work was authorised, the solicitor will typically:

1. Ask you to provide proof — a planning permission decision notice, a Lawful Development Certificate, or evidence that the work was completed more than 4 years ago
2. Require indemnity insurance — a one-off policy that covers the buyer against the risk of future enforcement action. This typically costs £50–£300 depending on the risk level.
3. Negotiate a price reduction — to account for the uncertainty and potential cost of resolving the issue
4. Delay or refuse to complete — if the risk is too high or no acceptable resolution can be found

Having a Lawful Development Certificate removes all of these problems. It is formal proof from the council that the development is lawful.

Mortgage: Your lender may require evidence that building work is authorised. If you cannot provide it, they may refuse to lend on the property, require you to regularise the work, or reduce the property’s valuation.

Insurance: Your buildings insurance may not cover unauthorised work. If the work causes a problem (for example, a structural failure in an unpermitted extension), your insurer could refuse the claim. Always notify your insurer before starting building work.

If you have already built without planning permission, you have several options:

1. Check if it was actually permitted development

Many homeowners assume they needed planning permission when they did not. If the work falls within permitted development rights, it was always lawful — you just did not have a certificate to prove it.

Use our free PD checker to check. If the work is PD, apply for an existing Lawful Development Certificate (Section 191) to get formal proof. This costs £274.

2. Apply for retrospective planning permission

You can apply for planning permission after the work is done. This is called a retrospective application. It is assessed the same way as any other planning application — there is no penalty for applying late, but there is also no guarantee of approval.

A householder retrospective application costs £548. If it is approved, you receive a decision notice confirming the work is authorised.

3. Wait for the 4-year time limit

If the building work was completed more than 4 years ago and no enforcement notice has been served, the development is immune from enforcement action. You can apply for an existing Lawful Development Certificate to confirm this.

Be careful: You need evidence that the work was completed more than 4 years ago — dated photographs, builder invoices, or other records. The burden of proof is on you.

4. Get indemnity insurance

If none of the above options work, indemnity insurance may be available. This is a one-off policy that covers the property owner against the cost of enforcement action. It is commonly arranged by solicitors during property sales.

Indemnity insurance is a safety net, not a solution. It does not make the development lawful — it just covers the financial risk. It typically costs £50–£300 and can be arranged quickly.

Important: Do not contact the council before arranging indemnity insurance. Most policies become void if the council has been notified or made aware of the issue.

If your situation is complex — for example, the work is recent, substantial, and clearly does not comply with planning policy — you may need professional advice. A planning consultant can assess your options and advise on the best approach. Typical fees are £200–£500 for a consultation, or £500–£2,000 to manage a retrospective planning application.

For straightforward cases where the work may be permitted development, our Permitted Development Certificate Report gives you a full PD assessment and application checklist for £39.

1. Check before you build. Use our free PD checker to find out whether your project is permitted development.
2. Get a Lawful Development Certificate. If your project is PD, an LDC costs £274 and gives you formal proof. Our PD Certificate Report helps you prepare the application.
3. Apply for planning permission if needed. If your project exceeds PD limits, apply before you start. A householder application costs £548 and takes around 8 weeks. See our full cost guide.
4. Do not forget building regulations. Most projects need building regulations approval too — this is separate from planning permission.
5. Check the Party Wall Act. If you are building near a boundary, you may need to serve party wall notices.