Boundary demarcation between heirs: how to avoid deadlock? The Court of Cassation ruling

Imagine you own land in Dax, inherited with your siblings. You want to fence it, but your neighbour disputes the boundary. You initiate a boundary demarcation action (judicial procedure to establish precise boundaries between two properties). Your co-heirs, uninterested, refuse to participate. Are you stuck? Until 2018, the answer was often yes. But a Court of Cassation decision changed everything.

This case precisely concerns this situation: heirs (the Y... siblings) owning a plot in co-ownership (property shared between several persons without physical division) who want to demarcate their land. The neighbour opposes this. The heirs bring legal action, but the court of appeal declares the action inadmissible on the grounds that it requires the agreement of all co-owners. The Court of Cassation quashes this judgment. Why? Because the boundary demarcation action is an act of administration, not an act of disposition.

In short, this decision frees heirs from a major constraint. It allows a single one of them to act to protect the common estate, without waiting for unanimity that is often difficult to obtain. But what exactly does this change for you, as an owner in Mont-de-Marsan, a tenant in Biscarrosse, or a real estate professional? This is what we will break down.

The facts: a story that happens every day

Mr and Mrs Y, owners of a cadastral plot in the Dax region, pass away. Their land, approximately 2,000 m², passes to their three children: Sophie, Paul, and Luc. They are in co-ownership, meaning they own the land together, without physical division. Sophie, who lives nearby, wants to build a fence. She consults a surveyor, who informs her of a disagreement with the neighbour, Mr Attendu, about the northern boundary. According to the plan, the boundary should follow an old hedge, but Mr Attendu claims it is further south, encroaching by 50 m².

Sophie proposes to her brothers to initiate a boundary demarcation action. Paul, based in Paris, is uninterested. Luc, in conflict with Sophie, refuses on principle. What to do? Sophie alone brings legal action against Mr Attendu to have the land demarcated. At the tribunal, Mr Attendu raises an objection: the action is inadmissible because Sophie does not have the consent of all her co-heirs. The tribunal rejects this objection and orders the demarcation. Mr Attendu appeals.

The court of appeal, in a judgment dated 2016, rules in favour of Mr Attendu. It considers that the boundary demarcation action, by definitively fixing the boundaries, modifies the extent (the physical consistency) of the co-ownership and thus constitutes a serious act requiring unanimous agreement. It declares the action inadmissible. Sophie, supported by her brothers who finally realise the stakes, lodges an appeal in cassation. On 12 April 2018, the Court of Cassation quashes the judgment. It rules that the boundary demarcation action falls into the category of acts provided for in Article 815-3 of the Civil Code, i.e., acts of administration.

The court's reasoning — broken down

The Court of Cassation relies on Article 815-3 of the Civil Code. This article distinguishes two types of acts concerning property in co-ownership: acts of administration (routine management, such as leasing or maintaining) and acts of disposition (serious acts, such as selling or mortgaging). For acts of administration, any co-owner can act alone. For acts of disposition, the agreement of all is required.

The question was therefore: is a boundary demarcation action an act of administration or disposition? The court of appeal had opted for the latter, arguing that demarcation fixes boundaries definitively, which affects the extent of the co-ownership. The Court of Cassation overturns this reasoning. It considers that demarcation has the sole purpose of recording and materialising pre-existing boundaries, not creating them. It is a preservative act that allows protection of the estate against encroachments, without altering its substance.

In other words, demarcating is like taking inventory: you do not change the property, you specify it. The Court recalls that this qualification as an act of administration is consistent with prior case law that admits a single heir can act to stop a nuisance (such as a construction encroaching on the land). It constitutes an evolution, as some courts previously hesitated. undefined, I have encountered cases where heirs, blocked by family disagreement, let a boundary dispute fester for years, resulting in loss of value. This decision ends this deadlock.

What this changes for you — concretely

If you are a landlord (you lease a property in co-ownership), this decision directly concerns you. Imagine: you lease a house in Biscarrosse with your cousins. The tenant reports a boundary conflict with the neighbour. Before 2018, everyone's agreement was needed to act, which could take months. Now, a single one of you can initiate demarcation, thus protecting the property and the tenancy relationship. Demarcation costs (approximately €1,500 to €3,000 depending on complexity) remain the responsibility of the co-ownership, but the action is possible without deadlock.

If you are a tenant, this reassures you: your landlord can more easily resolve a boundary dispute that could affect your enjoyment (for example, if the neighbour disputes access or the location of a terrace). If you are a purchaser, always check the state of boundaries before buying a property in co-ownership. A recent demarcation, even initiated by a single heir, offers legal security. If you are a co-owner, the principle is different (co-ownership falls under another regime), but the spirit is the same: routine management acts can be decided without unanimity.

Be careful, however: this decision does not allow an heir to sell the land alone (act of disposition). It only facilitates protection of boundaries. How to react? If you are in this situation, you should first attempt mediation with the neighbour. If this fails, consult a specialised lawyer to initiate the boundary demarcation action, even if your co-heirs are reluctant. Timelines: expect 6 to 18 months depending on the court (tribunal judiciaire of Mont-de-Marsan or other).

Four tips to avoid this type of dispute

• Have an amicable demarcation established upon acquisition or inheritance: even without conflict, a chartered surveyor can materialise boundaries with markers, for about €1,000 to €2,000. This prevents 90% of disputes.
• Keep all property documents: notarial deeds, cadastral plans, old leases. undefined, I have seen cases resolved simply with a 1950 plan found in an attic in Dax.
• Talk to your neighbours before any construction or fencing: a cordial discussion can avoid a lawsuit. If you are in co-ownership, appoint a representative among the heirs to manage these exchanges.
• Check easements (rights of way, for example) before acting: demarcation does not remove them. A notary or lawyer can help you identify them.

Deep dive: related case law and developments

Before this decision, case law was fluctuating. Some courts of appeal (like that of Bordeaux in 2010) already considered demarcation an act of administration, while others (like that of Douai in 2015) required unanimity. The Court of Cassation, through this ruling, unifies the doctrine. It fits into a broader trend of facilitating co-ownership management, visible also in other areas (such as the possibility for an heir to carry out urgent works alone).

What few people know is that this decision also applies to other similar acts, like the action to establish boundaries (when there is no disagreement but simple uncertainty). For the future, this means that courts, like that of Mont-de-Marsan, will be more inclined to accept boundary demarcation actions initiated by a single co-owner, thus accelerating dispute resolution. However, the Court specifies that the action must be diligently pursued in the common interest of the co-ownership, not for personal advantage.

Recap and next steps

Here is an FAQ to summarise:

• Q: Can an heir alone demarcate land in co-ownership? A: Yes, since the 2018 ruling, because it is an act of administration.
• Q: Do the other heirs need to agree to the costs? A: The costs are borne by the co-ownership, but the action can be initiated without their prior agreement.
• Q: Does this also work for a house? A: Yes, if the house is on land in co-ownership. Demarcation concerns the land boundaries.
• Q: What to do if my co-heirs refuse to pay their share? A: You can take legal action to recover their share, once demarcation is completed.
• Q: How long does a boundary demarcation action take? A: From 6 to 18 months, depending on complexity and the court.

In summary, before this decision, demarcation in co-ownership often required unanimity, blocking many cases. After, a single heir can act, effectively protecting the common estate.

Do you 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 →