Boundary Disputes & Proprietary Estoppel
Boundary disputes can be distressing, expensive, and deeply personal—especially when they involve neighbours you have lived alongside for years; one complex but crucial legal concept that often arises in these cases is proprietary estoppel. Understanding how this principle works can mean the difference between keeping land you believed was yours and losing it entirely.
In this guide, we explain in practical terms how Boundary Disputes & Proprietary Estoppel intersect, how the courts interpret these cases, and what steps you should take as a homeowner to protect your position.
What Is Proprietary Estoppel?
Proprietary estoppel is a legal doctrine used to stop (or “estop”) someone from denying another person’s rights over land where it would be unfair to do so. Typically, it applies where one party:
- Makes a promise or representation about land ownership, boundaries, or rights;
- The other party relies on that promise or representation to their detriment; and
- It would be unconscionable (legally unfair) for the promisor to go back on their word.
In boundary disputes, this can mean that even if you do not have formal legal title to a strip of land, you may still have a right to it if you have reasonably relied on your neighbour’s conduct or assurances.
Common Boundary Dispute Scenarios Involving Estoppel
Some of the most common examples of proprietary estoppel in boundary disputes include:
- Fences erected based on a shared belief: Neighbours agree (or assume) a fence marks the true boundary, but decades later one tries to reclaim land on the other side.
- Landscaping and improvements: A homeowner invests in paving, planting, or building on land with the other party’s knowledge and without objection.
- Verbal agreements or informal permissions: One neighbour says, “That bit’s always been yours,” or allows use without paperwork - then later disputes it.
In each case, the key issue is not just what the deeds say, but whether one party reasonably relied on the other’s conduct to their detriment, and whether allowing the other party to backtrack would be unfair.
Legal Ingredients of a Proprietary Estoppel Claim
To succeed in a claim for proprietary estoppel, courts typically look for three elements:
1. A representation or assurance: This doesn’t need to be written. It can be implied from conduct or silence. For example, if a neighbour watches you build a wall on their land and says nothing, that can count.
2. Reliance: You must have acted in reliance on the assurance. This could include financial expenditure, effort, or giving up other opportunities.
3. Detriment: There must be some form of loss or disadvantage. Simply believing something isn’t enough - you must have suffered a consequence.
If these conditions are met, the court will consider whether it would be “unconscionable” for the person who made the assurance to deny your claim.
How Courts Decide Proprietary Estoppel in Boundary Disputes
Court decisions in this area are very fact-sensitive. Judges look closely at:
- All conduct between the parties over time
- The clarity of the representations made
- Evidence of reliance and detriment (e.g., receipts, photos, witness statements)
- Whether the parties behaved reasonably and in good faith
If proprietary estoppel is proven, courts have broad discretion to grant remedies. These can include:
- A declaration that you own or have a right to the land in dispute
- An order preventing your neighbour from reclaiming the land
- Compensation or an easement
Key Case Example: Thorner v Major [2009]
While not strictly about a boundary, the House of Lords decision in Thorner v Major illustrates the power of proprietary estoppel. In that case, a farmer repeatedly implied he would leave his farm to his cousin, who worked unpaid for years based on those suggestions. When the farmer died without a will, the court upheld the estoppel claim - even though no explicit promise had been made.
The principles are directly relevant to boundary disputes. Silence, implied promises, or informal understandings can all carry legal weight.
How Estoppel Interacts with Land Registry and Title Plans
Many homeowners are surprised to discover that the Land Registry’s boundary lines do not define the legal boundary with certainty. Title plans are based on Ordnance Survey maps and are only general boundaries, not precise legal lines.
That’s why disputes often arise over small slivers of land - and why proprietary estoppel can override what the title plan shows. Even if a strip of land lies outside your registered title, you may still claim it if you meet the conditions of estoppel.
Practical Steps for Homeowners
If you are currently in - or at risk of - a boundary dispute where proprietary estoppel may apply, follow these steps:
1. Gather evidence – Collect all emails, letters, texts, photos, and receipts that show what was said or done. Old photos showing fence positions or improvements can be crucial.
2. Get a professional boundary survey – A chartered surveyor can help assess where the boundary likely lies and identify features of long-standing possession.
3. Speak to a property lawyer – Estoppel claims are legally technical and best handled with professional guidance. A solicitor can advise on your likelihood of success and next steps.
4. Act promptly – Delay can damage your case, especially if your neighbour is taking active steps to assert ownership or alter the land.
5. Try to resolve amicably – Courts favour parties who attempt resolution before litigation. Courts and advisors often encourage the parties to pursue mediation..
Defending Against an Estoppel Claim
If a neighbour brings an estoppel claim against you, don’t panic - but don’t ignore it either. Consider:
- Whether any assurances were actually made
- If their reliance was reasonable
- Whether they truly suffered a detriment
- Whether you challenged or objected early on
Early legal advice can often help narrow the dispute or achieve settlement before it escalates.
Costs and Risks
Estoppel based boundary disputes often involve court proceedings, surveyors, and solicitors. Costs can easily reach several thousand pounds or more - especially if the case goes to trial. However, if successful, the court may order the losing party to pay some or all of the winner’s legal costs.
Even so, many parties settle their cases before trial once they disclose the evidence. The strength of your documentary evidence and legal argument will influence your position significantly.
Conclusion
Boundary Disputes & Proprietary Estoppel raise complex legal and emotional issues. The law recognises that not every arrangement over land is formal - and that fairness sometimes requires giving effect to informal understandings. If your disputed boundary depends on what the parties said or agreed years ago, estoppel may offer a powerful legal remedy.
But each case turns on its own facts. If you're unsure whether you have a claim or need to defend one, seek professional advice as soon as possible.
Need Help with a Boundary Dispute?
At Anstey Horne, we specialise in boundary disputes and have deep experience in cases involving proprietary estoppel. Our surveyors and legal partners work together to help homeowners resolve complex land disputes with clarity and confidence.
Our chartered surveyors provide:
- Accurate boundary surveys
- Expert witness reports compliant with court standards
- Support with mediation, legal teams, and Land Registry submissions
We collaborate with solicitors and barristers to build your case on solid, defensible evidence while also identifying cost-effective solutions where possible.
We combine technical expertise with in-depth legal understanding to help you achieve clarity and avoid costly conflict.
For advice direct from one of our Surveyors, please call our Enquiry line on 020 4534 3135.
If you would rather we called you instead, please fill in our Contact form and we will be in touch.
For more information on all aspects of Boundary Disputes see the collection of articles in our blog.
For advice direct from one of our Surveyors, please call our Enquiry line on 020 4534 3135.
If you are planning work that is covered by the Act, or if you have received notice of work from a neighbour and want advice on how best to protect your property please contact:
Geoffrey Adams
BEng (Hons) PgDip FRICS
Senior Director
Party Walls
London
Rickie Bloom
BSc (Hons) MRICS
Senior Director
Party Walls
London