Raising a Party Wall: When Your Neighbour Builds on Your Extension

You live in Aix-en-Provence, in a semi-detached house with a garden. To gain more light, you had the party wall raised on your side, at your own expense. So far so good. But one morning, you are astonished to discover that your neighbour has placed beams on your raised section to create a terrace. What can you do? Can he appropriate your construction by simply offering to pay his share? The Court of Cassation has ruled: no. And its decision of 22 March 2006 (No. 05-10.093) is a textbook case for all owners of party walls.

The issue is simple: when you raise a party wall without your neighbour's help, that raised section belongs to you alone. Your neighbour has no right to use it without your consent, even if he offers to acquire party ownership (i.e., to become co-owner of that part). The Court of Cassation states unambiguously: one cannot impose co-ownership on property that is exclusively yours.

But beware: this decision only concerns the private raised section. If both neighbours contribute, the rules change. Full analysis of the judgment and its practical consequences for you, owners in Arles, Aix-en-Provence or elsewhere.

The facts: a story that happens every day

Mr and Mrs B., owners of a house in Aix-en-Provence, one day decided to raise the party wall separating them from their neighbours, Mr and Mrs C. They carried out this raising at their exclusive expense, without any contribution from their neighbours. The raised wall thus became their private property, the lower part remaining party. So far, nothing unusual: everyone can raise a party wall at their own expense, and the raised section belongs to them (Article 658 of the Civil Code).

But a few years later, Mr and Mrs C. decided in turn to build a new raised section above that of the B.s. To do so, they ‘cut out’ part of the B.s' roof and placed their construction on the existing raised section. Furious, the B.s took the matter to court to obtain demolition of the structure. They considered that their neighbour had infringed their right of ownership by appropriating their private raised section without authorisation.

Before the Court of Appeal, the C.s retorted that they were willing to acquire party ownership of the B.s' raised section, in accordance with Article 660 of the Civil Code (which allows a neighbour to become co-owner of a party wall by reimbursing half its value). The Court of Appeal agreed and dismissed the B.s' claim for demolition. The B.s appealed to the Court of Cassation. The Court of Cassation upheld their appeal and quashed the appellate decision, on the ground that the Court of Appeal had failed to draw the legal consequences from its own findings: it had noted that the B.s' raised section was private and that the C.s' construction encroached on their property, but nevertheless validated the forced acquisition of party ownership. However, Article 660 does not allow imposing co-ownership of a private property on its exclusive owner: party ownership can only be acquired over a wall that is already party, not over a private part. The case was therefore remanded to a different Court of Appeal.

The reasoning of the court — explained

The crux of the dispute concerns the interpretation of Articles 658 and 660 of the Civil Code. Article 658 provides that ‘any co-owner of a party wall may raise it, but at his exclusive expense; the raised section belongs to him alone’. Article 660 provides that ‘the neighbour who did not contribute to the raising may acquire party ownership of it by paying half the cost it incurred and half the value of the land provided’. The question therefore was: can a neighbour, by his sole will, become co-owner of a private raised section?

The Court of Cassation answers no. It recalls that Article 660 only applies to party walls, i.e., already common walls. The raised section built by one co-owner becomes his exclusive property from the moment of construction. The neighbour cannot acquire it by force: he must obtain the owner's consent. In this case, the Court of Appeal had indeed noted that the B.s' raised section was private and that the C.s had ‘cut out’ the roof – which constitutes an infringement of property rights. But then it considered that the mere declaration by the C.s of their wish to acquire party ownership was sufficient to regularise the situation. This is an error of law: one cannot transform private property into common property without the consent of its owner.

The decision is in line with consistent case law: private property is protected against encroachments, even if the perpetrator offers compensation. The trial judges must verify whether the raised section is actually party or private before applying Article 660. Here, they disregarded the principle that no one can be forced to give up his property (except for public utility purposes, with compensation).

In short, the Court of Cassation reaffirms that party ownership cannot be imposed: it must be negotiated. If your neighbour builds on your raised section without your consent, he commits a trespass. You can demand demolition, even if he offers to pay.

What this means for you — practically

If you are the owner of a party wall that you have raised at your own expense, this decision is a protection. You are the sole master of that raised section. Your neighbour cannot lean his construction on it, install pipes, or even put up a fence without your written authorisation. If he does, you can obtain in court the demolition of the structures and damages for the harm suffered (for example, loss of enjoyment of your roof or costs of restoration).

Let's take a concrete example: in Arles, an owner raises a party wall by 1.50 m to create a terrace. Cost of works: €8,000. Two years later, his neighbour builds a garden shed against this wall, using the raised section as support. The initial owner can demand demolition of the shed, even if the neighbour offers to reimburse half the cost of the raised section. Why? Because the raised section is private property, not party. Article 660 does not apply.

If you are a tenant, you must be careful: you do not have the right to raise a party wall without the owner's consent. However, if your landlord has done so, you benefit from the same protection as him against encroachments by the neighbour.

For buyers, always check the origin of ownership of raised sections. A wall may appear party when its top part is private. A surveyor can help clarify any ambiguity.

Finally, if you are in litigation, note that the limitation period for action is five years for abnormal neighbourhood disturbance (Article 1240 of the Civil Code). But if the encroachment constitutes a trespass (construction without right), you can act without time limit as long as the structure exists. undefined, I have come across cases where a simple beam placed on a raised section led to two years of proceedings and €15,000 in costs. Better safe than sorry.

Four tips to avoid this type of dispute

• Have a condition survey carried out before works: before raising a party wall, have a bailiff's report or surveyor's report made. This will prove the initial condition and the neighbour's lack of participation. Keep all invoices.
• Inform your neighbour in writing: even if you do not need his authorisation to raise the wall, send him a registered letter with acknowledgement of receipt informing him of your works. This will avoid misunderstandings and can serve as evidence in case of dispute.
• Negotiate a written agreement if your neighbour wants to use your raised section: if he wishes to lean a construction on it or acquire party ownership, require a notarial deed or a signed agreement before a notary. Set the price (half the cost of the raised section, current value) and maintenance conditions.
• In case of encroachment, act quickly: as soon as you notice a construction on your raised section without agreement, send a formal notice by registered letter with acknowledgement of receipt demanding demolition within 15 days. If nothing happens, apply to the judicial court in summary proceedings for an expert assessment and demolition under penalty. Do not wait: the longer time passes, the more the neighbour may argue peaceful possession.

Besoin d'un conseil personnalisé ? Contactez Maître Zakine — première consultation 30 min à 45€.

Further reading: related case law and developments

This 2006 decision confirms a consistent line of case law. Already in 1999, the Court of Cassation had held (Civ. 3e, 10 February 1999, No. 97-10.110) that the raising of a party wall by a single co-owner is his exclusive property, and that the neighbour can only acquire party ownership with his consent. More recently, a judgment of 4 July 2019 (No. 18-17.456) specified that Article 660 does not apply when the raising was carried out before the parties acquired the wall: express agreement is required.

The trend is therefore towards reinforced protection of the initial owner. Courts are increasingly strict on proof of party ownership. If there is doubt, they presume the wall is party (Article 653 of the Civil Code), but the private raised section remains an exception that must be proved by the person relying on it.

For the future, case law is likely to continue in this direction. The question could arise for solar panels or technical equipment fixed on a raised section: again, the owner's consent will be necessary.

Frequently asked questions

Can I raise a party wall without my neighbour's consent?
Yes, Article 658 of the Civil Code allows you to do so, at your exclusive expense. But you must comply with planning regulations (building permit or prior declaration depending on height).

My neighbour built on my raised section without my consent. Can I force him to demolish?
Yes, you can apply to court for demolition of the structure, as it constitutes an encroachment on your private property. The 2006 decision confirms this.

What if my neighbour offers to pay half the cost of the raised section?
You are not obliged to accept. Article 660 only applies to party walls, not private raised sections. You can refuse and demand removal of any construction.

What are the time limits for taking legal action?
For abnormal neighbourhood disturbance, you have 5 years from the manifestation of the damage. For a trespass (construction without right), the action is imprescriptible as long as the structure exists.

How much does a procedure for encroachment on a raised section cost?
Expect between €3,000 and €10,000 in legal and expert fees, depending on complexity. Mediation may be cheaper (€500 to €2,000) and faster.

Are you 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 →