You built without planning permission. Now you need to sell.
Illegal extensions create massive problems during conveyancing. Buyers can’t get mortgages, and solicitors raise red flags immediately.
I’ve purchased properties with unauthorised building work. Kitchen extensions, loft conversions, conservatories – all built without consent.
I’m Saif Derzi, founder of Property Buyers Today. I’ve been buying non-standard properties since 2015.
This guide explains your options with illegal extensions. You’ll discover retrospective planning permission, certificates of lawfulness, and indemnity insurance.
I’ll also show you when regularisation makes sense and when selling as-is becomes your best option.
- Why Illegal Extensions Create Problems When Selling
- Different Routes for Selling with Unauthorised Extensions
- What You Must Disclose About Illegal Building Work
- Costs of Dealing with Unauthorised Extensions
- How Illegal Extensions Impact What Buyers Will Pay
- Obstacles to Traditional Sales with Illegal Extensions
- Selling Your Property with Illegal Extensions to Property Buyers Today
Why Illegal Extensions Create Problems When Selling
Illegal extensions have no planning permission or building rules approval. Both are needed for most building work. Missing either one causes big problems.
Rear extensions need permission. Loft conversions need it too. Even conservatories need approval in many cases.
Buyers find out during surveys. Their surveyor spots work without certificates. Banks then refuse mortgages immediately. I’ve watched sales die within days of survey reports arriving.
Common illegal work:
- Rear extensions
- Loft conversions
- Garage conversions
Old work might be safe now. Extensions over four years old usually can’t be touched by councils. Loft conversions need ten years before becoming legal automatically.
Building rules are different from planning permission. You need both. I’ve seen extensions with planning permission but no building certificate. Banks still won’t lend.
Planning issues and building rules failures both kill sales. Selling with illegal extensions means finding cash buyers only.
Check government guidance before any building work starts.
Different Routes for Selling with Unauthorised Extensions
Here are the 3 primary approaches to sell your property when an illegal extension exists…
Estate Agents
The conventional route presents severe obstacles for houses with illegal extensions:
- Standard sale duration: 6-12 months (extended timeframe – mortgage lenders reject properties with unauthorised building work)
- Many sales fall through when solicitors discover the extension lacks planning permission
- You need agents experienced with illegal extension properties and planning applications
- You’ll encounter these costs:
- Agent commissions (up to 3%)
- Solicitor fees (up to £4,000)
- Planning advice and consultations (£500-£1,500)
- Retrospective planning applications (£206-£462 fee plus costs)
- Enforcement action defence if required (£2,000-£10,000)
- Very limited buyers interested in properties with illegal extensions
Property Buyers Today
When an illegal extension makes your property challenging to market:
- We can complete within just 7 days
- No financing complications or planning permission needed
- What you gain:
- No agent fees
- We handle legal costs
- No property viewings – we buy illegal extension properties as they stand
- No application expenses – we manage planning issues ourselves
- We understand planning law and enforcement procedures
- Completion date you can trust
- Trade-off: Obtain up to 85% of property value (often better after application costs and enforcement risks)
Professional cash house buyers like Property Buyers Today understand illegal extension complications and handle all procedures.
Property Auction
Auctioning attracts purchasers who deal with illegal extension properties:
- Duration: 3-4 months
- Sale finalises instantly when gavel drops
- Key factors:
- Property sold as-is – bidders understand planning breach
- Attracts specialist developers and experienced investors
- Perfect for regularisation projects – draws suitable buyers
- Extension status disclosed in auction legal pack
- Wait 4-8 weeks until auction date
- Wait 28 days to finalise transaction
- Registration fees (up to £1,000)
- Auction house charges (up to 6%)
- Full illegal extension details must be disclosed to all bidders
Review our guide on selling a house at auction to understand how this process works for properties with illegal extensions.
What You Must Disclose About Illegal Building Work
You must tell buyers about illegal extensions. Property forms ask directly about planning permission. They ask about building rules, too. Lying here is fraud.
Surveyors request all building certificates. Your solicitor needs planning permission documents. Missing paperwork raises red flags immediately.
I’ve seen buyers cancel sales and sue sellers for hiding illegal work. Courts call it fraud. You could face prosecution. Your buyer can void the whole contract.
Documents needed:
- Planning permission
- Building certificates
- Completion certificates
Trading Standards take false statements seriously. Hiding building work breaks consumer protection laws. Penalties include big fines and court cases.
Estate agents must warn viewers about unauthorised work. Their rules require honesty. They can’t hide major problems.
Being upfront actually helps sales progress. Buyers know what they’re getting. They bring cash instead of needing mortgages. I’ve helped sellers find buyers who understand the situation.
Get all documents ready before listing. Missing certificates means finding specialist buyers only.
Costs of Dealing with Unauthorised Extensions
Unauthorised extensions cost thousands to sort out legally. Understanding these costs helps you decide whether to fix problems or sell as-is.
Retrospective Planning
Getting planning permission after building costs £500-£3,000+.
Council application fees are a few hundred pounds. Architects and planning consultants charge for drawing plans and handling paperwork. Simple cases cost less. Complicated extensions cost more.
You might get rejected.
Councils can refuse retrospective planning if your extension breaks the rules. Then you’ve paid fees for nothing and still have illegal work.
Building Control Certificates
Regularisation applications cost £1,000-£5,000+.
Building control inspects your extension and checks if it meets safety rules. You pay for inspections, paperwork, and certificates. Bigger extensions cost more to regularise.
Selling houses without building regulations certificates needs this paperwork sorted first.
You might need to do extra work to pass inspections. Opening up walls for checks costs money. Fixing things that don’t meet rules costs even more.
Structural Surveys
Engineer reports cost £500-£2,000.
Structural engineers check if your extension is safe. They look at foundations, walls, and roof structure. Banks and councils need these reports before approving anything.
You often need multiple surveys.
One before applying, another during inspections, and more if problems get found. Each survey costs hundreds.
Remedial Work
Fixing non-compliant work costs £2,000-£20,000+.
You might need to add proper foundations, fire doors, or ventilation. Electrical work might need redoing. Damp proofing might be missing. Selling houses with building regulation issues often needs expensive fixes.
Some extensions can’t be fixed.
If your extension is too big or in the wrong place, you might need to demolish it completely. This wastes all your original building costs.
Indemnity Insurance
Insurance against enforcement risk costs £100-£500, usually.
This protects you if the council takes action later. It covers legal costs and some compensation. Check building regulations information to understand what insurance covers.
Insurance doesn’t fix existing problems.
It only covers future council action. It won’t help with mortgage rejections or buyer concerns right now.
Legal Fees
Solicitor costs for complicated sales are £1,500-£3,000+.
Selling with illegal extensions needs extra legal work. Your solicitor handles indemnity insurance, disclosure paperwork, and buyer questions. Complex cases cost more.
Legal fees stack up quickly.
Every complication adds to costs. Cases dragging on for months cost even more in legal bills.
How Illegal Extensions Impact What Buyers Will Pay
Illegal extensions slash property values hard. Expect drops between 15-40% for serious cases. Missing building certificates hurt the worst.
Banks won’t lend money on homes with unauthorised work. This cuts out 90% of buyers immediately. Only cash buyers remain interested.
I’ve seen three-bedroom homes worth £300,000 with certificates sell for £180,000 without them. That’s a £120,000 loss from illegal building work.
Price killers:
- No planning permission
- Missing building certificates
- Failed council inspections
Cash buyers know you’re desperate. They offer low prices because your options are limited. I’ve helped sellers choose between accepting low offers or spending thousands getting late permission.
Values recover after getting certificates. Apply for late planning permission. Get building rules signed off properly. Your home becomes mortgageable again.
Buyers use illegal work to negotiate hard. Surveyors highlight every missing certificate. Buyers then demand huge price cuts to cover their risk.
Properties become un-mortgageable without proper approvals. Understanding your home’s true value means facing this reality early.
Obstacles to Traditional Sales with Illegal Extensions
Illegal extensions make normal house sales nearly impossible. Estate agents struggle because legal problems scare buyers away fast.
Mortgage Rejections
Banks refuse loans for properties without proper certificates.
About 95% of buyers need mortgages. Lenders won’t release money for properties with illegal extensions. No building control certificates means automatic rejection.
Your buyer pool drops to cash purchasers only.
The few cash buyers left know you’re desperate. They make very low offers, expecting you to accept.
Valuer Concerns
Surveyors give low valuations or refuse to value properties with illegal work.
They flag missing certificates and unpermitted extensions. Banks use these low valuations to reject mortgages. Some surveyors won’t complete reports at all.
Buyers see these reports and walk away.
Even cash buyers get nervous when surveyors highlight serious problems. Low valuations give them excuses to offer much less money.
Council Enforcement Risk
Buyers worry about future planning enforcement notices.
The council can force the removal of illegal extensions anytime. Buyers don’t want to inherit this risk. They imagine costly demolition and legal fights with the council.
This fear kills most sales fast.
Even if enforcement seems unlikely, buyers won’t take chances. Their solicitors warn them about worst-case scenarios.
Sale Collapses
Most sales fall through when illegal extensions get discovered.
Everything seems fine until solicitors check the planning and building control records. Missing certificates and unpermitted work get flagged immediately. Buyers panic and pull out.
You’ve wasted weeks and paid legal fees for nothing.
Starting again with new buyers leads to the same problems. Understanding why your house isn’t selling often links to illegal extensions that buyers can’t overlook.
Solicitor Advice
Conveyancers tell their clients not to buy properties with illegal extensions.
They warn about mortgage problems, enforcement risks, and resale difficulties. Even buyers who love your house listen to their solicitor’s advice.
Legal professionals protect their clients from bad purchases.
Solicitors see illegal extension problems constantly. They advise walking away rather than taking risks.
Extended Timescales
Retrospective applications add months to normal sales.
Getting planning permission takes 8-13 weeks. Building control regularisation takes another 6-12 weeks. Everything moves slowly through council processes.
Every delay risks the sale collapsing.
Buyers get fed up waiting and find other houses. Their mortgage offers expire. What should take 12 weeks stretches to 6-12 months or never completes at all. Selling property with enforcement notices faces similar timeline problems. Check the Planning Portal guidance for application timescales.
Selling Your Property with Illegal Extensions to Property Buyers Today
Let me be straight about this…
An illegal extension creates a legal nightmare when selling. Buyers demand retrospective planning permission, solicitors raise red flags, and mortgage companies often refuse to lend. If you’d rather not spend months dealing with the council and uncertain outcomes, I completely understand.
I need to be clear—we won’t offer the full market price because we factor in our own costs and aim to resell relatively quickly.
But here’s why homeowners with unauthorised building work still decide to sell their house fast with us…
Speed
Most house sales take months, but we can buy your property in as little as 7 days.
This quick process is perfect if you need to move soon or want to avoid being stuck in a long chain of buyers and sellers. We have the cash on hand so don’t need to wait for mortgages or a chain to collapse.
Guaranteed Sale
Did you know 1 in 3 sales fall through on the open market?
We know how frustrating it is to get 6 months into a process and have a buyer pull out.
When we give you the final price for your house, that’s the amount you’ll get. Guaranteed!
No Costs
You won’t face any costs with us.
We handle all the expenses involved in buying your property, including legal fees and surveys. You get cash in your bank when the sale is complete, and there are no surprise estate agent commissions to worry about.
No Stress Or Hassle
Our team supports you through the whole selling process.
We keep you updated about what’s happening and answer any questions quickly. You’ll always understand what’s going on with your sale and what happens next.
Free Property Valuation
Our property experts will value your house at no cost to you.
They look carefully at your property and check local market prices to give you an accurate figure. This professional service comes with no obligations.
No Viewings Required
Forget about cleaning and tidying for viewings.
We don’t need multiple visits or open houses to make our offer. This means no strangers walking through your home, and no disruption to your daily life.
All Properties Welcome
Whether your house needs work or is in perfect condition, we’ll buy it.
We have experience with all types of properties and conditions. This means you can sell your house to us no matter what state it’s in.
Professional Legal Service
Our expert team manages all the legal requirements for you.
We work with experienced property lawyers who make sure everything runs smoothly, and put your property at the top of their list. This gives you peace of mind that your sale is being handled properly from start to finish.
