Selling a House With Unpermitted Work: Planning & Building Regs

By Lisa Hayes · 7 November 2026

You can sell a house with an extension, loft conversion or other alteration that was built without planning permission or building regulations sign-off, but you have to deal with it, not hide it. Planning and building regulations are two separate systems with two separate fixes, and which one bites depends on what was built, when it was finished and where in the UK you are. Most sales that wobble over this do so because nobody sorted out which problem they actually had.

I'll say this up front because I see it go wrong so often: the paperwork gap is rarely the end of your sale. The delay almost always comes from finding out late. A buyer's solicitor spots it six weeks in, the mortgage lender gets nervous, and a deal that looked solid turns into a renegotiation. Find it first and you control the story.

Planning permission vs building regulations: what is the difference?

This is the bit that trips people up, and honestly it trips up some estate agents too. They sound like the same thing. They are not.

Planning permission is about whether the development is acceptable at all: how big it is, what it looks like, how it affects neighbours and the street. It is decided by your local planning authority, usually the district or borough council. Plenty of small extensions and loft conversions are built under permitted development rights, which means no application was needed, but the work still has to meet the conditions of those rights.

Building regulations are about whether the work is safe and sound: structure, fire escape, insulation, drainage, electrics, ventilation. Almost every extension and loft conversion needs building regulations approval, whether or not it needed planning permission. The sign-off is a completion certificate from building control, or from an approved inspector.

Why does the split matter? Because the solutions are different, the timescales are different and the risks to a buyer are different. A missing completion certificate is a safety question. A missing planning permission is a legal-status question. Lenders care about both.

Why does unpermitted work stop a sale?

Three reasons, in the order they usually appear.

First, the paperwork request. Early in the conveyancing process your solicitor will ask you to complete the TA6 property information form, which asks directly whether any building work has been done, and whether planning permission and building regulations sign-off were obtained. If you've never seen it, our guide to the TA6 property information form walks through it line by line. Answer it truthfully. A wrong answer here is the sort of thing that comes back to haunt sellers after completion.

Second, the searches and the survey. The buyer's solicitor will check the council's planning history. A surveyor may spot a loft that looks newer than the paperwork says, or a rear extension that isn't on the title plan. Neither needs to be dramatic. A mismatch between what's standing and what's recorded is enough to trigger an enquiry.

Third, the lender. Mortgage lenders instruct solicitors to check that planning and building regulations were complied with. If the answer is "we don't know", plenty of lenders will want a fix before they release funds. That is where a buyer on a mortgage can quietly drop out, and why this problem sits close to the wider issue of material information you must give buyers. Estate agents now have to disclose certain material facts on the listing itself. Unpermitted work that you know about belongs on that list.

How do I find out what paperwork I actually have?

Before you panic, work out what you have. Many sellers assume there is a problem when there isn't, because the papers are simply in a drawer or with a previous solicitor.

1. Dig out your own purchase file. Your conveyancer's completion pack, or the pack you got when you bought, often includes planning decisions and completion certificates for earlier work.
2. Search the council's online planning register. Most councils let you search by address. You are looking for decision notices, approved drawings and any lawful development certificates.
3. Ask building control for the building regulations history. Councils keep records of applications and completion certificates for their area. Work signed off by an approved inspector should leave you with a final certificate in your own hands.
4. Check any specialist certificates. Replacement windows installed since 2002 should have a FENSA or similar certificate. Our FENSA certificate guide covers what to do if yours has gone missing.
5. Ask the previous owner or their agent, if you can reach them. It sounds obvious. It works more often than you'd expect.

Once you've done that, sort the work into three piles: things that have approval, things that never needed it, and things you can't evidence. The third pile is the one to focus on.

Is unpermitted work my problem if the previous owner did it?

Yes. This surprises people. Planning breaches and building regulations failures attach to the property, not to the person who carried them out. If you bought a house in 2016 with a conversion that was never signed off, you inherited the gap. You may have a claim against whoever sold it to you if their paperwork was misleading, but that is a separate, slower process and not a way to fix a live sale.

The flip side is helpful. You do not have to prove you built it. You only have to show what happened and when, which matters a lot in the next section.

How long does the council have to take action over planning breaches?

Here is where the law has changed recently, and where plenty of articles online are out of date.

In England, councils used to have four years to take enforcement action against building works and against a change of use to a single home, after which the breach became immune. Other breaches had 10 years. From 25 April 2024 the Levelling-up and Regeneration Act 2023 swept away the shorter period, replacing it with a single 10-year limit. The Planning Inspectorate set this out in its guidance on the changes.

• 4 yearsold immunity period for works substantially completed before 25 April 2024
• 10 yearssingle enforcement limit for breaches on or after 25 April 2024
• 25 April 2024the date the change took effect in England

The important detail is the transition. The 10-year limit applies where the building work was substantially completed on or after 25 April 2024, or the change of use to a single dwellinghouse happened on or after that date. Works finished earlier keep the four-year period. In plain terms: an extension built in 2019 without permission has probably already become immune. One finished in 2025 will not be for ten years.

Two things to flag. One: these changes apply to England. The commentary I read on the reform says Wales was not included, and Scotland and Northern Ireland run their own systems, so don't assume the same dates apply there. Two: a solicitor writing about the reform noted that proving the completion date will matter, and suggested evidence like dated photographs, invoices and statutory declarations. I'd treat that as good practice whatever your date.

If you want to check where the council stands on a particular breach, our existing guide on selling with a planning enforcement notice covers what happens when the council has already acted.

What is a lawful development certificate, and should I get one?

A lawful development certificate, often shortened to LDC or called a certificate of lawfulness, is a document from the council confirming that something already built or already in use is lawful, even though it never had planning permission. Councils describe it as establishing whether an existing use of land, operational development previously undertaken, or an activity in breach of a planning condition is lawful. West Berkshire Council, for one, explains it exactly that way on its certificate of lawfulness page.

It is not compulsory. Buckinghamshire Council's page says as much. But it turns an uncomfortable "we think the time has run out" into a piece of paper your buyer's solicitor can file. That is worth a lot.

On cost, councils publish their own fees. As one example, Buckinghamshire lists the fee for an existing-use certificate as "£293 or relevant full application fee", and half the full fee for a proposed one. I can't tell you which figure applies to your case, because that council's page does not say, so check your own council's fee schedule before you budget. Councils also set their own timescales, so ask how long they are currently taking before you commit to a completion date.

When is it worth it?

• When the work is more than four years old and was finished before 25 April 2024, and you have evidence of when it was done.
• When the work fell within permitted development but you never recorded that formally.
• When your buyer's solicitor has said they will not proceed without it.

When is it not worth it? When the breach is recent, because the certificate cannot be granted if the time has not passed. And when the cost and wait outweigh the problem, which brings us to indemnity insurance in a moment.

What evidence do you need for a lawful development certificate?

The councils I looked at do not publish a full evidence list on their landing pages, so I'm not going to pretend there is a statutory checklist. What helps in practice is anything that fixes the date the work was finished: dated photographs, builders' invoices, utility or council tax records showing when a new room came into use, and a statutory declaration from you or from someone who watched the work happen. The more independent the evidence, the better. A neighbour's declaration carries more weight than your own.

Should I apply for retrospective planning permission instead?

Sometimes, but it is a bigger gamble than most sellers realise. A retrospective application asks the council to approve something that already exists. If they say yes, you are done. If they say no, you have just drawn their attention to a breach and may have made enforcement more likely.

Councils can also issue an enforcement warning notice, a tool that invites you to submit a retrospective application when development has taken place in breach of planning control. Issuing one counts as taking enforcement action. And where a regularisation application has already been made, the right to appeal on the ground that permission should be granted is restricted in some cases. These are changes brought in alongside the 10-year rule.

My view: if the work is clearly harmless and well built, a retrospective application can make sense. If the work is out of keeping with the area, close to a neighbour's boundary, or you have had any dispute with the neighbours, speak to a planning consultant before you submit anything. A neighbour dispute is exactly the sort of thing that turns a quiet paperwork gap into a complaint to the council.

What is a building regulations regularisation certificate?

This is the building regulations route. The Planning Portal describes a regularisation application as a retrospective application relating to previously unauthorised works, meaning works carried out without building regulations consent, started on or after 11 November 1985. The result is a certificate of regularisation. The Planning Portal page on regularisation also says it applies even if the work was done before you owned the property.

What happens next is where sellers get nervous. The council will arrange to inspect the work. The Planning Portal notes that exposure, removal or rectification of works may be necessary to establish compliance. In practice that can mean lifting floorboards, opening up a ceiling to see the joists, or showing the steel to the inspector. And the fee varies with the level of work, so I won't quote a number.

What if the council inspects and finds something wrong?

Then you have a choice, and it is a better choice than finding out in the buyer's survey. The council will say what needs doing for the work to comply. You can do it, you can price it in and sell, or you can sell to someone who will take it on. What you can't do is un-know it.

How long can a council enforce building regulations?

One commonly cited time limit is that a section 36 enforcement notice under the Building Act 1984 cannot be served more than 12 months after the work was completed. That figure comes from a community-written reference page rather than the statute, so treat it as a rule of thumb and ask a solicitor if it matters to your case. The important point is that the short enforcement window does not remove the problem. The buyer's solicitor still wants the certificate. Lenders still want the certificate. The absence of a certificate is what shows up in a search, not the council's appetite to chase you.

Can I use indemnity insurance instead?

This is the shortcut most sellers hear about first, and for good reason: it can work. An indemnity policy is a one-off premium that protects the buyer and their lender against financial loss if the council later takes action over a specific, defined defect, such as missing building regulations sign-off on an old conversion. Our dedicated guide on indemnity insurance when selling a house goes through the types of policy.

My honest view on where it helps and where it doesn't:

If the work involves structure, gas or electrics, I'd be reluctant to rely on a policy at all. A policy pays out on a financial loss. It won't stop a loft staircase failing a fire inspection. For anything where someone could be hurt, get it properly inspected.

What are my options if I just want to sell?

Line them up honestly, because they suit different sellers.

On that last route, a cash buyer is not buying a mortgage lender's approval, so the lender's paperwork requirements do not apply in the same way. That is why unpermitted work often pushes sellers towards cash house buyers. But a good cash buyer will still price the risk, so you should expect a discount. Our guide to what percentage of market value cash buyers pay gives you a sense of how offers are usually pitched. And if the problem is part of a bigger list, such as a house that struggles on several fronts, our page on how to sell an unsellable house is a useful companion.

What will a cash buyer or investor actually ask about?

They'll ask the same questions a solicitor would: what was built, when it was finished, who did it, and what paperwork exists. They'll want dated photographs if you have them. And they will want to know whether anyone has complained. A buyer who can see the full picture can price it with confidence, which is why good disclosure usually gets a better offer than a vague one.

If you're thinking about this route, selling your house fast explains how the process works and what to expect from a legitimate buyer.

A sensible order of play

1. Establish the facts. What was built, when it was finished, and what paperwork you have.
2. Sort the work into planning and building regulations. They need separate fixes.
3. Check the dates. Was the work substantially completed before 25 April 2024? That decides which enforcement clock applies in England.
4. Get an independent view of the work. A chartered surveyor or a structural engineer can tell you whether it is sound before you spend money on certificates.
5. Take advice before approaching the council. Particularly if you are considering indemnity insurance, because the order matters.
6. Choose your route. Fix, insure, disclose and sell, or sell as-is.
7. Disclose it on the TA6 and tell your agent. Straight away, not at the last minute.

The mistakes I'd steer you away from

• Hoping nobody notices. Searches and surveys are built to notice. If you answer the TA6 wrongly, the problem becomes a misrepresentation claim rather than a paperwork gap.
• Assuming "it's been there for years" means it's lawful. Time can make planning breaches immune, but only if you can show when the work was finished. Without evidence, you have a story and not a certificate.
• Confusing the two systems. A planning decision doesn't prove building regulations were met, and the other way round.
• Ringing the council before you have a plan. Not because the council is the enemy, but because your options narrow once a file is opened. Take advice, then decide.
• Paying for a certificate you don't need. If the work was permitted development and the paperwork is simply missing, a copy from the council's own records may cost far less than a retrospective application.
• Leaving it to the buyer's solicitor to raise. That is when you have the least leverage and the shortest time.

What about Scotland, Wales and Northern Ireland?

Each is different, and I would not apply the English dates to any of them. The 25 April 2024 changes covered England; commentary on the reform said Wales was not included. Scotland uses building warrants and completion certificates rather than building regulations approval, and its own planning enforcement rules. If you're selling north of the border, our guide to selling a house in Scotland covers how the process differs, and a Scottish solicitor should advise on the paperwork itself.

Common scenarios, and what I'd do

These are illustrative examples rather than case studies, but they show how the logic plays out.

A loft conversion done years ago with no completion certificate

Check first whether it needed planning permission at all. Many do not. Then check building regulations. Often the planning side is fine and the gap is the missing completion certificate. A regularisation certificate or, if the work looks sound and the lender is willing, an indemnity policy are the usual routes. Our guide on selling a house with a loft conversion goes deeper on the specifics, such as stairs, fire escape and head height.

A rear extension that went beyond what was approved

This is where I'd get specialist advice quickly, because the work may be outside both the permission and any permitted development rights. If it was substantially completed before 25 April 2024 and more than four years ago, it may be immune and a lawful development certificate could help. If it is newer, the 10-year clock applies and the safer routes are a retrospective application or a sale to a buyer who is comfortable with the risk.

A garage converted into a room

Very common, often missing both paperwork and sometimes proper insulation and damp-proofing. See our guide to selling a house with a garage conversion for the checks buyers make.

Work left half finished

A different problem again, because there's no completion to certify. We cover it in selling a house with unfinished building work.

How do I keep this from derailing a sale?

Treat the paperwork like any other part of preparing the house. Gather it early, put it in a folder, and hand your solicitor a complete pack before you list. If a gap exists, decide your route before the first viewing. Buyers who see a tidy file with a clear plan feel safe. Buyers who see a surprise feel suspicious, and they price accordingly.

And one last thing, because it is easy to feel this is all your fault. It usually isn't. Unpermitted work is one of the most common issues in UK conveyancing, partly because the rules have changed so often and partly because builders sometimes skipped the sign-off and left owners to find out later. You're not the first, and you won't be the last. There's almost always a route through.

Ready to see what your house could sell for?

If you'd like to know what your options look like with the house exactly as it stands, you can compare offers from vetted buyers with no obligation. It costs nothing to see the numbers, and you can walk away if the sums don't work. Lisa Hayes and the Ready Steady Sell team are independent, so the aim is simply to put the choices in front of you.