Party Wall: When a Wall is Presumed Party Only on Both Sides

Imagine the scene: you have just bought a flat with a lovely terrace in Beausoleil, on the heights of Monaco. The wall separating your property from your neighbour's, on the sea side, seems firmly anchored. But now your neighbour, to install a pergola, drills through this wall without asking your opinion. "This wall is a party wall, I have the right," he tells you. You thought it belonged to you alone. Who is right? This is the question that every owner may ask themselves one day, and it is precisely the one that the Court of Cassation decided in a judgment of 7 March 1973.

The answer is not as simple as it seems. Article 653 of the Civil Code creates a presumption (a rule that holds true until proven otherwise): any wall separating two buildings is deemed to be a party wall, i.e. belonging half to each owner. But beware: the presumption only applies if there are two buildings, one on each side of the wall. And if on one side there is only a garden or a courtyard? The presumption fails. This is what the Court of Cassation recalled in this judgment, in favour of the owner who had alone built the wall.

In short, this 1973 decision is still relevant today and could overturn your rights if you own a contiguous wall. So how do you know if your wall is a party wall or not? And what should you do if your neighbour uses it without permission? Deciphering.

The facts: a story like any other

Mr X, owner in Monaco, owned a plot of land on which he had a Bornage et limites de propriété">boundary wall built along the dividing line with his neighbour, Mr Y. On his side, Mr X had built a house that leaned against this wall. On Mr Y's side, however, the land was left as a small garden, with no construction. Years later, Mr Y decides to carry out works: he drills through the wall to install a rainwater drain, then fixes a fence to it. Mr X opposes this and sues his neighbour to obtain the removal of the structures and damages (financial compensation for the harm suffered).

The court of first instance (Tribunal de grande instance) finds in favour of Mr Y, holding that the wall is presumed to be a party wall under Article 653 of the Civil Code. For the judges, the signs of party ownership (such as coping stones or corbels) were not sufficiently probative to rebut the presumption. Mr X appeals, but the Court of Appeal upholds the judgment. He then appeals to the Court of Cassation.

The Court of Cassation quashes the appeal judgment, on the ground that the presumption of party wall under Article 653 cannot apply when there is a building on only one side of the dividing wall. In this case, only Mr X had built against the wall; Mr Y had no construction. Consequently, the wall must be presumed to belong entirely to Mr X, unless proven otherwise. The case is remitted to another Court of Appeal.

The reasoning of the court — dissected

To understand this judgment, one must first grasp the mechanism of Article 653 of the Civil Code. This provision states: "In towns and countryside, any wall serving as a separation between buildings up to the eaves, or between courtyards and gardens, and even between enclosures in the fields, is presumed to be a party wall, unless there is a title or mark to the contrary." In other words, if a wall separates two buildings, the law considers it to belong equally to the two owners, unless a deed (title) or visible signs (marks) prove otherwise.

But the Court of Cassation here specifies an essential condition: for the presumption to apply, there must be two buildings, one on each side. If only one side is built, the wall is not "serving as a separation between buildings" within the meaning of Article 653. In that case, the wall is presumed to belong to the owner of the built side, because it is he who bore the cost of construction and derives the benefit from it.

Note, however, that the presumption can be rebutted by contrary marks, such as a coping (upper part of the wall in the shape of a roof) sloping on one side only, or corbels (projecting stones) indicating exclusive ownership. But in this case, the marks invoked by Mr Y were not convincing. The Court of Cassation therefore logically restored Mr X's right.

What few people know is that this solution is not new: it stems from a consistent interpretation of Article 653. The trial judges (tribunal and Court of Appeal) had nevertheless made a mistake by applying the presumption without verifying the condition of double building. The Court of Cassation simply set the record straight.

What this means for you — concretely

This decision has direct implications for all owners, whether landlords, tenants or buyers. Let's take examples.

Landlord in Beausoleil: You rent out a flat whose terrace wall overlooks the neighbour's garden. If your tenant installs an aerial on this wall, and the neighbour objects, you need to know whether the wall is a party wall or not. If on your side there is a building (the block) and on the other side only a garden, the wall belongs entirely to you. You can therefore authorise the works without asking the neighbour's consent. However, if the neighbour later builds a garden shed against this wall, the situation could evolve: the wall could become a party wall if the building is sufficiently characterised.

Buyer of a house in Nice: During a sale, the notary must mention whether the wall is a party wall or private. If the deed does not specify, the presumption in Article 653 applies. But if you buy a house with a wall that runs along an undeveloped plot, check carefully: in the absence of a building on the neighbour's side, the wall belongs to you. This can have an impact on the value of the property (a private wall gives you more rights).

Co-owner in Monaco: Dividing walls between co-ownership lots are often party walls, but beware of extensions. If a co-owner builds a conservatory against a wall that only borders a single building, the wall may become private again. undefined, I have come across cases where a co-owner had drilled through a wall to create an opening, and the management company wrongly objected, believing the wall to be a party wall. Checking the existence of buildings on each side is crucial.

If you are in this situation, you must act quickly: in the event of encroachment (use of the wall without right), you can apply to the court for removal of the structures and damages. The limitation period is 5 years from the discovery of the disturbance (Article 2224 of the Civil Code). The amounts may vary: for a simple drilling, expect €1,000 to €5,000 in damages, but if the wall is damaged, the cost of reinstatement can be much higher.

Four tips to avoid this type of dispute

• Check party wall status before any property purchase: Ask your notary to examine the title deeds and carry out a survey of the dividing walls. If the wall is presumed to be a party wall, it must be mentioned in the sale deed. If in doubt, consult a surveyor.
• Keep evidence of the wall's construction: If you had a wall built at your expense, keep the invoices, plans and photos. In the event of a dispute, these documents can rebut the presumption of party wall.
• Never drill through a wall without written consent: Even if you think the wall is a party wall, obtain your neighbour's written permission. A simple verbal agreement can be contested. If the wall turns out to be private, you risk legal action.
• In case of dispute, have the marks of party wall status recorded: Instruct a bailiff (huissier de justice) to draw up a report (constat) of the visible marks (coping, corbels, etc.). This report can be produced in court to prove the private nature of the wall.

Further reading: related case law and developments

The solution in the judgment of 7 March 1973 has been confirmed by subsequent decisions. For example, the Court of Cassation held that the presumption of a party wall also does not apply when the wall only separates courtyards or gardens without a building (Civ. 3e, 16 June 1999, No. 97-17.914). In other words, a building is required on each side for the presumption to operate.

Conversely, if both properties have constructions, even partial ones, the presumption becomes applicable again. For example, a simple lean-to (small roofed structure) may be considered a building. The courts assess the notion of "building" on a case-by-case basis: a garage, a shed or a conservatory may suffice. The trend is therefore towards a flexible interpretation, but the condition of double construction remains firm.

For the future, this case law remains stable. It is unlikely that the legislature will amend Article 653, as it strikes a good balance between interests: it favours the owner who built the wall (presumption of exclusive ownership in the absence of a building on the neighbour's side) while protecting the neighbour who has built (presumption of party wall).

Summary and next steps

What to do if you are affected:

1. Identify the type of wall: Check whether there is a building on each side. If yes, the wall is presumed to be a party wall. If no, it is presumed to be private to the owner of the built side.
2. Check the titles: Consult your deed of ownership. If party wall status is mentioned, it is conclusive, subject to error.
3. Look for marks: Observe the coping (slope) and corbels. A coping with two slopes indicates party wall status; a single slope indicates exclusive ownership.
4. Consult a lawyer: If a dispute arises, a lawyer specialising in property law can analyse your situation and take the necessary steps (letter before action, claim form).

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