Should You Buy a Property That Has Been Converted Without Planning Permission?
The Surprising Answer Is Yes. Read to Find Out Why.
If you’re a first-time buyer, new property developer, or aspiring investor in the UK, the idea of buying a property without planning permission might sound like a costly mistake. And you’d be right to proceed with caution — but also wrong to walk away entirely.
In today’s competitive market, properties that seem “too risky” to most are often the most lucrative opportunities when approached correctly. These are the properties the banks won’t lend on, the auction rooms whisper about, and most buyers ignore. But with the right bridging finance strategy and a clear understanding of planning options, they can be your ticket to high returns and below-market entry points.
At Sunrise Commercial Finance, we’ve helped clients across the UK secure funding for unmortgageable properties, unauthorised conversions, and planning uplift projects. Here’s why buying a property with no planning permission could be the smartest move you make in property.
Why Is Planning Permission So Important?
If a property has been converted — say, from a single dwelling to flats, or from a shop into a house — without planning consent, several issues arise:
- Mortgage lenders won’t fund it – making it unmortgageable.
- The local council can issue an enforcement notice – requiring changes to be reversed or demolition carried out.
- Fines can be imposed – with potential daily penalties for ongoing breaches.
- You could inherit legal liabilities – even if the work was done by a previous owner.
- No guarantee of retrospective permission – applying after the fact may not work.
Despite all that — or perhaps because of it — these properties can be bought at a heavy discount.
The Opportunity: Why Buy a Property Without Planning Permission?
The answer is simple: undervalued potential.
Most buyers shy away from complicated planning issues, which pushes down demand and price. That means:
- You can often buy at 20–40% below market value.
- You gain a value uplift if you resolve the planning issues.
- Bridging loans give you a route to finance the purchase and planning journey.
- The property becomes mortgageable or sellable once planning is sorted.
Your Three Options After Purchase
Once you own the property, you have several routes forward:
1. Undo the Conversion
Return the property to its original use (e.g., converting flats back into a single house). This satisfies planning enforcement and can allow you to refinance.
2. Apply for Retrospective Planning Permission
If the changes were recent, apply for full permission for the existing use. While not guaranteed, it can legitimise the current setup.
3. Use the “10-Year Rule” or Apply for a Certificate of Lawful Use
If the property has been in the same use without enforcement for 4 or 10 years (depending on the change), you may be eligible to apply for a Certificate of Lawful Development or Lawful Use, essentially grandfathering in the current setup.
How to Finance It: Bridging, Refurbishment & Planning Loans Explained
Traditional mortgages won’t touch these properties — but bridging lenders will, especially when backed by a solid exit strategy.
🔹 Bridging Loans
- Short-term loan (usually 3–24 months)
- Used to buy unmortgageable property quickly
- Ideal when planning permission is pending or being applied for
🔹 Refurbishment Bridging Loans
- Similar to a standard bridge, but includes funds for refurb work
- Great if you’re restoring the property to its original use
- Can include internal repairs, reconfigurations, and compliance upgrades
🔹 Planning Improvement Bridging Loans
- Specifically designed for properties where planning uplift is the main value driver
- Lenders assess the future value of the property with planning in place
- Excellent for developers who plan to legalise and sell/refinance
Each of these loans can be arranged without traditional income proof, using the property itself as security. At Sunrise, we guide clients step-by-step and find the best bridging solution for their specific project and exit strategy.
Real-World Example
One of our clients recently bought a commercial unit that had been converted into four flats without planning permission. It was unsellable on the open market and rejected by every mortgage lender. With a planning improvement bridge, they bought it at a 35% discount and applied for lawful use under the 10-year rule.
The result?
- Retrospective permission granted
- Valuation increased by £175,000
- Re-mortgaged onto a buy-to-let portfolio product
- Bridging loan repaid within 8 months
Common Mistakes to Avoid
- Assuming retrospective planning is guaranteed – it’s not.
- Not checking enforcement history – speak to the local council before buying.
- Failing to plan your exit strategy – you need a clear route to refinance or sell.
- Using the wrong broker or lender – many won’t understand planning risk.
- Underestimating legal fees and timescales – make sure your solicitor is experienced with planning irregularities.
Frequently Asked Questions (SEO-Targeted)
❓ Can I get a mortgage on a property without planning permission?
No — not from standard lenders. You’ll need bridging finance until the planning issue is resolved.
❓ What is a Certificate of Lawful Use?
It’s legal confirmation that a property has been used in a certain way long enough (4 or 10 years) to be lawful, even if it didn’t have planning permission originally.
❓ Is it illegal to buy a property without planning permission?
No — buying it isn’t illegal. But owning and continuing the unauthorised use could lead to enforcement action.
❓ How long does it take to get retrospective planning permission?
Typically 8–12 weeks, but delays can occur. Be prepared for longer if appeals are involved.
❓ What are the risks of the 10-year rule?
You must prove continuous use for 10 years without interruption or enforcement. Gaps or complaints can invalidate your case.
Glossary of Key Terms
Unmortgageable: A property that cannot be financed through a standard mortgage due to legal, structural, or planning issues.
Bridging Loan: A short-term loan used to bridge a gap between buying a property and refinancing or selling it.
Retrospective Planning Permission: Permission applied for after building works or changes have already taken place.
Certificate of Lawful Use/Development: A legal document from the council stating that a use or development is lawful.
10-Year Rule: A planning rule allowing lawful use applications if a use has continued uninterrupted for 10 years.
Final Word: Don’t Be Afraid of the Problem Properties
Buying a property without planning permission isn’t for the faint of heart — but it is for the strategic investor. With expert advice and the right financial structure, these “problem properties” become profitable projects that can be refinanced, re-sold, or retained as income-generating assets.
Let us guide you through the process — from deal analysis to completion.
Get Expert Help Today
Sunrise Commercial Finance is a trusted UK specialist in:
- Bridging loans
- Development finance
- Auction purchases
- Planning gain funding
📞 Speak to an expert today at: www.sunrisecommercial.co.uk
📩 Or get in touch for a no-obligation consultation.
For more information contact us for a fees free chat.
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