Party Walls: When Encroachment Prevents You from Acquiring a Common Wall

Imagine you own a house in Dax, in the Arènes district. You have a wall separating your garden from your neighbour's. For thirty years, you've maintained it, repainted it, even hung your climbing roses on it. One day, you learn that this wall isn't entirely on your land: it slightly encroaches on the neighbouring plot. What happens then? Can you claim party wall status (the status of a common wall) for this wall?

This question, much more common than one might think, was decided by the Court of Cassation in a decision that is now a reference. Property owners in the Landes department, whether in Mimizan near the lake or in the historic centre of Mont-de-Marsan, often find themselves facing this type of situation. Old walls, uncertain property boundaries, constructions that overhang... How does the judiciary handle these cases?

The answer is clear: an encroachment (a construction that extends onto a neighbour's land) prevents the acquisition of party wall status. In other words, if your wall isn't entirely on your land, you cannot become co-owner with your neighbour simply through the passage of time. But what does this mean concretely for you? And how to avoid the pitfalls?

The facts: a story that happens every day

Mr. and Mrs. Durand, owners of a house in Dax since the 1970s, had a party wall (shared) with their neighbours, the Martins. This wall separated their two gardens. In 2002, the Martins sold their property to a developer who built a block of flats. During the works, it appeared that the wall wasn't entirely on the boundary line: it encroached by about 15 centimetres onto the new owners' land.

The Durands, who had maintained this wall for decades, then invoked the acquisition of party wall status by prescription (acquisition through the passage of a certain period). They considered that, since this wall had been there for more than thirty years and they had always maintained it, it should be considered a party wall along its entire height. They even requested forced cession of party wall status (the obligation for the neighbour to sell them half of the wall) for the part above ground level.

The developer, however, contested this claim. He argued that the initial encroachment prevented any acquisition of party wall status. The case went all the way to the Court of Cassation, after twists and turns before the first instance and appeal courts. The Durands hoped that the highest civil court would rule in their favour, but the verdict was unequivocal.

The court's reasoning — analysed

The judges of the Court of Cassation recall a fundamental principle: Article 552 of the Civil Code states that "ownership of the land carries with it ownership of what is above and below." In plain terms, if you own a piece of land, you also own what is above and below it. But be careful: this doesn't mean you can build anywhere!

The court relies on Article 545 of the Civil Code, which prohibits deprivations of property without legal cause. An encroachment constitutes an infringement of another's property rights. So, how could one acquire party wall status for a wall that, from the outset, encroaches on the neighbour's land? That would reward the person who committed a fault!

The judges analyse the arguments of both parties. The Durands invoke the thirty-year prescription (acquisition through thirty years of use) and the regular maintenance of the wall. The developer responds that the initial encroachment vitiates the entire process. The Court of Cassation rules in favour of the developer: an encroachment prevents the acquisition of party wall status. It thus confirms a consistent line of case law, but forcefully reiterates this principle.

What few people know: party wall status can only be acquired if the wall is built exactly on the boundary line. As soon as there is encroachment, even minimal, the door is closed. In other words, no co-ownership possible on a poorly placed wall!

What this changes for you — concretely

If you are a landlord (who rents out a property), this decision directly concerns you. Imagine you rent out a house in Mimizan, near the beach. Your tenant reports a problem with the neighbour's wall. You discover it encroaches 10 cm onto your land. Before this decision, you might have thought time was on your side. Now, you know that encroachment blocks everything. You must act quickly: have the encroachment recorded by a chartered surveyor (cost: €800 to €1,500 depending on complexity), then demand demolition or compensation.

For tenants, the situation is different. You are not the owner, but you have maintenance obligations. If you notice an encroachment, report it immediately to your landlord. Don't start maintaining a wall that isn't entirely on the rented land!

Purchasers must be particularly vigilant. When buying a house in Mont-de-Marsan, always have the property boundaries checked. An unresolved encroachment can reduce the property value by 5 to 15%. undefined, I've encountered cases where sales were cancelled due to encroachments discovered after signing.

How to react if you're in this situation? First step: consult a lawyer solicitor. Second step: instruct a chartered surveyor. Third step: attempt mediation with the neighbour before considering legal action.

Four tips to avoid this type of dispute

• Always have a boundary survey (precise delimitation of land) carried out by a chartered surveyor before building any wall. This is the only way to ensure the wall will be exactly on the boundary line.
• Carefully keep all your title deeds and plans. They are essential in case of dispute. Digitise them to avoid losing them.
• Check for easements (rights that one owner has over another's land) before buying. An encroachment can be hidden by a right of way or water drainage easement.
• Act quickly if you notice an encroachment. Don't wait thirty years! Prescription periods vary, but the longer you wait, the more complicated the situation becomes.

In-depth analysis: related case law and developments

This decision fits into a consistent line of case law. Already in 1995, the Court of Cassation had ruled that "an encroachment prevents the acquisition of party wall status" (Cass. 3rd civ., 15 March 1995, no. 93-15.789). It thus confirms a firm guiding principle.

On the other hand, there are divergent decisions on ancillary points. For example, some courts have allowed regularisation of encroachments by amicable agreement between neighbours. But be careful: this requires a notarial deed and the consent of both parties. The trend in the courts is clear: strengthened protection of property rights, refusal to validate irregular situations.

For the future, this case law means property owners must be increasingly vigilant. With the digitisation of cadastral plans and measurement drones, encroachments are increasingly easily detectable. Disputes risk multiplying if constructions don't scrupulously respect boundaries.

What you absolutely must remember

Before this decision: Some thought an old encroachment could be regularised by prescription. After this decision: An encroachment always prevents the acquisition of party wall status, regardless of how long it has existed.

Numbered checklist "What to do if...":

1. If you notice a wall encroaching on your land: immediately consult a lawyer solicitor.
2. If you plan to build a wall: first have your land surveyed by a chartered surveyor.
3. If you're buying a property: systematically check boundaries and any potential encroachments.
4. If you're in dispute with a neighbour: first attempt mediation before initiating legal proceedings.

Find yourself in a similar situation? A first 30-minute consultation with Maître Zakine (€45) can save you months of proceedings — and often much more. Book an appointment →