Party Wall: Can a Co-owner Modify It Without the Others' Consent?

Imagine: you own a house in Bordeaux, in the Chartrons district. Your neighbour, without warning, decides to lower the party wall separating your two gardens by 80 centimetres over 6 metres in length. He wants to gain more light. You lose privacy. The question that then arises is simple: did he have the right to do so? And above all, what does the law say when a property is held in co-ownership (several people own it)? This is precisely what the Court of Cassation ruled in a judgment of 7 March 1989, which continues to set precedent today.

In this case, an organisation (PACT du Douaisis) took the initiative to repair a party wall, but unilaterally lowered it. One of the co-owners (joint owners) then brought proceedings to have the wall restored to its original height. The central legal question was whether this legal action was a 'conservatory act' (an act aimed at preserving the property) that any co-owner can undertake alone, or whether it required the consent of all co-owners.

The Court of Cassation's answer is clear: an action which does not have the purpose of removing the jointly owned property from imminent peril is not a conservatory act. In other words, one cannot modify a party wall without the consent of all co-owners, except in cases of absolute urgency. This decision, handed down over thirty years ago, remains a reference for all neighbour disputes concerning party walls in France, and particularly in the Bordeaux area where many old co-ownership properties exist.

The Facts: An Everyday Story

The story begins in the North of France, but could just as easily have taken place in Bordeaux or Libourne. The PACT (association for the promotion of housing) of Douaisis intervenes on a party wall – a wall owned half by two neighbouring owners. Without informing the other owner, Mr X, the PACT repairs the wall but takes the opportunity to lower it by 80 centimetres over a length of 6 metres. Mr X, discovering the facts, is furious: his privacy is compromised, and the value of his property could suffer. He then brings a possessory action (an action protecting possession of property) to have the wall restored to its original height, under a penalty payment (financial penalty per day of delay).

The first instance court rules in his favour. But the PACT appeals, arguing that Mr X, as a co-owner, could not act alone in court for this type of claim. According to the PACT, only all the co-owners together could have brought the action. Mr X retorts that it is a conservatory act – an urgent action to preserve the property – and that, as provided for in Article 815-2 of the Civil Code (which allows any co-owner to take measures necessary for the preservation of the property), he could act alone.

The Court of Appeal follows Mr X's reasoning. But the Court of Cassation quashes the judgment: Mr X's action was not a conservatory act, because it did not aim to avert an imminent peril. The wall was not in danger of collapsing; it was merely a nuisance between neighbours. Therefore, Mr X should have obtained the consent of all other co-owners before taking legal action. This judgment perfectly illustrates a common situation where one owner acts alone, thinking they are doing the right thing, and comes up against the complexity of co-ownership law.

The Reasoning of the Court — Analysed

To understand the decision, one must first know the basic rule: according to Article 815-2 of the Civil Code, 'any co-owner may take measures necessary for the preservation of jointly owned property'. This is called a conservatory act. For example, if a wall is threatening to collapse, a single co-owner can call a bricklayer urgently, without waiting for the others' consent. This is logical: urgency prevails.

But in this case, the Court of Cassation considered that Mr X's action – seeking restoration of the wall to its original height – did not aim to avoid an imminent peril. The wall had already been lowered, and there was no immediate danger to the safety or integrity of the property. It was rather a matter of remedying a neighbour nuisance, which falls under ordinary litigation. However, to bring such an action in court, Article 815-2 is not sufficient: the consent of all co-owners is required, or failing that, an authorisation from the judge (Article 815-3 of the Civil Code).

The Court therefore reiterated that the concept of a conservatory act is interpreted strictly: it covers only urgent acts indispensable for the preservation of the property. In this case, Mr X's action was not urgent – it could await a collective decision. The judges thus made a subtle but fundamental distinction between 'preservation' (maintaining the existing state) and 'reinstatement' (restoring a previous state). This decision is neither a reversal nor an evolution: it confirms previous case law, but it is often cited because it lays down a clear principle.

What few people know is that this case also raises the question of the legitimacy of the PACT's action. By modifying the wall without consent, the PACT committed a voie de fait (an illegal act infringing property rights). But the Court did not rule on this point, as the proceedings were focused on the admissibility of Mr X's action. In short, even if the PACT was wrong on the merits, the procedural form prevented Mr X from obtaining justice quickly.

In other words, this decision teaches us that co-ownership law is a delicate balance between protecting the property and the freedom of each co-owner. If you are in a similar situation, remember this: to act alone, urgency must be demonstrated. Otherwise, it is better to consult a lawyer specialising in property law, such as Maître Zakine, to know how to proceed.

What This Changes for You — Practically

This decision has very practical implications, whether you are an owner, a landlord (owner who lets), a tenant, or a co-owner.

For a co-owner: You cannot, alone, bring legal action to have a party wall modified by a neighbour restored, except in case of urgency (imminent peril). You must obtain the consent of all other co-owners. If one of them refuses, you can apply to the judge for authorisation. undefined, I have come across cases where a Bordeaux property owner let his neighbour lower a wall without reacting, thinking he could act alone later. Result: he had to convince three other co-owners, losing six months.

For a tenant: You are not the owner, so you cannot bring legal action for this type of dispute. It is the owner (landlord) who must do so. But you can notify them in writing (registered letter) so that they act. Concrete example in Libourne: a tenant saw his neighbour modify the garden party wall; he alerted his landlord, who had to obtain the co-owners' consent before taking action. Without this consent, the action would have been inadmissible.

For a buyer: Before purchasing a property, check whether any work has been carried out on party walls without consent. If so, you could inherit a dispute. Have a party wall survey carried out by a chartered surveyor. In Bordeaux, in the Chartrons area, some co-ownership properties have party walls dating from the 18th century, and rights are often poorly defined.

For a co-owner in joint ownership: Remember that any important decision (modification of a wall, sale, long-term lease) requires unanimity, except in an emergency. If you want to avoid deadlock, consider a joint ownership agreement (a contract organising the management of the property). Cost: around €500 with a notary, but it can save you much higher legal costs.

Four Tips to Avoid This Type of Dispute

• Before any work on a party wall, obtain written consent from all co-owners. Even for a simple repair, if it changes the appearance or height, consent is necessary. Send a registered letter with acknowledgment of receipt detailing the work. Keep the replies.
• In case of disagreement, apply to the interim relief judge for an urgent authorisation. If you believe the wall is threatening to collapse, you can act alone in summary proceedings (urgent procedure) to have the peril recorded. But beware: you must prove urgency (expert report, photos, witness statements).
• Have a description of the division and a set of co-ownership rules drawn up if the property is jointly owned. These documents clarify everyone's rights over the common parts (including party walls). Without them, conflicts are frequent. In Libourne, I saw a case where the absence of rules blocked the sale of a property for a year.
• Consult a lawyer lawyer before taking legal action. A professional will check whether you can act alone or whether you need to gather the co-owners. The cost of a consultation (around €150) is negligible compared to the costs of a lost case due to inadmissibility.

Further Reading: Related Case Law and Developments

The decision of 7 March 1989 is part of a consistent line of case law. For example, in a judgment of 24 March 1993 (No. 91-15.432), the Court of Cassation held that the installation of a fence on jointly owned land is not a conservatory act, because it does not respond to an imminent peril. Similarly, a judgment of 12 July 2018 (No. 17-21.421) recalled that improvement works (changing windows, insulation) are not conservatory and require unanimity.

The trend of the courts is therefore to restrict the notion of a conservatory act to only urgent and indispensable measures. This means that for any project modifying the jointly owned property (even minor), it is imperative to obtain collective consent, on pain of nullity of the action.

For the future, with the multiplication of co-ownerships and joint ownerships (particularly in the city centres of Bordeaux and Libourne), these questions will remain crucial. A legislative development could clarify the notion of 'conservatory act' by including certain acts of routine administration, but for now, the case law is stable.

Summary and Next Steps

FAQ:

• Can I lower a party wall to gain more light? No, without the written consent of all co-owners. Even if the wall is in poor condition, you must repair it identically, except in a life-threatening emergency.
• What if my neighbour modifies the wall without my consent? Send him a formal notice by registered letter to restore the wall to its original state. If he refuses, consult a lawyer to take legal action. Beware: you will need to justify the consent of the other co-owners or a judicial authorisation.
• What are the time limits for acting? The possessory action must be brought within one year of the disturbance (Article 1264 of the Code of Civil Procedure). After this period, you lose your rights. Do not delay.
• How much does legal action cost? Count between €1,500 and €5,000 in lawyer's fees for summary proceedings, and up to €10,000 for a full trial. Expert fees (around €800) may be added. A preventive consultation is therefore much cheaper.

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