Party Wall: When Planning Permission Does Not Create a Right of Ownership

Imagine: you own a house in Tarnos, in the Landes. Your neighbour asks your permission to build a boundary wall exactly on the dividing line between your two plots. You agree, orally or by a brief written note. Years later, you sell your house. The buyer discovers that the wall straddles the boundary and thinks he becomes half-owner. But what is the reality?

This situation, more common than one might think, raises a fundamental legal question: is a simple agreement between neighbours sufficient to transfer ownership of a wall? The Court of Cassation, in a judgment of 4 March 1971 (No. 69-12.140), ruled: an act by which an owner authorises his neighbour to build astride the boundary line, without evidencing a modification of property rights, is not subject to land registration. In other words, party wall rights (common ownership of a dividing wall) are not acquired by a mere authorisation.

This judgment, although dating from 1971, remains relevant for all owners and real estate professionals. It reminds us of a fundamental rule: ownership is not presumed, it must be proven by a title (notarial deed) or by thirty years' adverse possession. So, how should you react if you are in this situation? Let us decipher this decision and its practical implications.

The facts: a story that happens every day

Mr X, owner in Biscarrosse, owns a house with a garden. His neighbour, Mr Y, wishes to build a boundary wall along the dividing line. To save space, Mr Y proposes to build the wall astride the line, i.e. half on Mr X's land. Mr X agrees by a private deed (a simple non-notarial writing) in which he specifies that the wall "would remain his full ownership until such time as Mr Y or his successors in title wish to acquire the party wall rights".

Years pass. Mr X dies, and his heirs sell the house to a third party, Mr Z. The latter discovers that the wall is astride the boundary and considers that he has become co-owner by virtue of the authorisation deed. He brings proceedings to have the party wall rights recognised. The Court of Appeal rules in his favour, holding that the authorisation deed constituted a modification of property rights and should have been registered with the land registry (land registration). In the absence of registration, the deed was unenforceable against Mr Z, who could therefore claim party wall rights by prescription (thirty years' adverse possession).

Mr Y, the builder of the wall, appeals to the Court of Cassation. He argues that the authorisation deed did not modify property rights: the wall remains the exclusive property of Mr X, unless the party wall rights are acquired subsequently. The Court of Cassation agrees with him and quashes the appeal judgment. But what exactly does this change?

The reasoning of the court — analysed

The Court of Cassation relies on the principle that ownership is a real right (a right over a thing) which, to be enforceable against third parties, must be registered with the land registry. Article 28 of the Decree of 4 January 1955 (relating to land registration) requires the registration of all acts "evidencing a modification of property rights". In clear terms, if an act transfers or modifies ownership, it must be recorded with the land registry service, failing which it cannot be invoked against a third-party purchaser.

In this case, however, the authorisation to build astride the boundary line does not transfer ownership of the wall. It merely permits construction on another's land, without modifying the ownership. The Court specifies that the act "does not evidence any modification of property rights" and is therefore not subject to land registration. In other words, even without registration, this agreement remains valid between the parties (Mr X and Mr Y) and their successors in title (heirs, purchasers).

The Court also dismisses the argument of acquisitive prescription (thirty years' adverse possession). To acquire party wall rights by prescription, the wall must have been possessed as owner for 30 years. However, Mr Y built the wall under an authorisation, which precludes possession "as owner" (he possessed under a precarious right). What few people know is that possession must be peaceful, public, unequivocal and as owner. Mere tolerance or authorisation does not allow prescription.

This decision confirms constant case law: party wall rights can only result from a title (notarial deed) or from thirty years' unequivocal adverse possession. It also reminds us that a written agreement between neighbours, even precise, does not amount to a transfer of ownership if it is not characterised as such.

What this changes for you — practically

For owners: if you authorise your neighbour to build a party wall, do not think you automatically become co-owner. You must require a notarial deed evidencing the creation of an easement (real right) or a deed of sale of the party wall rights. Failing that, the wall remains the property of the person on whose land it is built, even if it crosses the boundary. Concrete example: in Biscarrosse, an owner authorised his neighbour to build a 10-metre wall astride the boundary. The neighbour paid for the construction. Thirty years later, the owner sells his house. The purchaser cannot claim party wall rights, because the authorisation was not registered and does not constitute a title.

For purchasers: before buying a property, check the title deeds and ask for a notarial certificate regarding the party wall rights of dividing walls. Do not rely on appearances. If a wall is astride, ask the seller to produce the party wall deed or proof of thirty years' adverse possession. If you are in this situation, you should consult a notary or a specialised lawyer before signing.

For notaries and estate agents: this judgment reminds you of the importance of land registration. Any act modifying real rights (easement, party wall, etc.) must be registered to be enforceable against third parties. A mere authorisation to build is not sufficient. undefined, I have come across cases where an owner had given verbal authorisation, and the purchaser ended up in dispute with the neighbour. To avoid this, have an authentic deed drawn up.

Four tips to avoid this type of dispute

• Tip 1: Formalise any agreement by notarial deed. If you authorise your neighbour to build on the boundary, or if you wish to acquire party wall rights, have an authentic deed drawn up by a notary. This deed must be registered with the land registry to be enforceable against future purchasers. Expect notarial fees of around €500 to €1,000, depending on the value of the wall.
• Tip 2: Check the deeds before buying. When purchasing property, ask the seller to provide all deeds relating to party walls or easements. A surveyor can also carry out a boundary survey to clarify the limits. The cost of a boundary survey is around €1,500 to €2,500, but it avoids much more costly disputes.
• Tip 3: Do not presume party wall rights. In French law, a dividing wall is presumed to be party wall only if it is built astride the boundary (Article 653 of the Civil Code). But this presumption can be rebutted by a contrary title deed. So do not rely on mere appearance.
• Tip 4: In case of dispute, consult quickly. If your neighbour builds a wall that encroaches on your land, or if you discover an undeclared party wall, act quickly. Acquisitive prescription runs from the construction. Legal action must be brought within 30 years. A consultation with a specialised lawyer (around €150 to €300) can save you years of proceedings.

Further reading: related case law and developments

The Court of Cassation confirmed this position in a later judgment of 23 November 1988 (No. 87-13.514), where it held that "the authorisation to build a wall on the boundary line does not, by itself, constitute a title of ownership in favour of the person who obtained it". In other words, the case law is consistent: an authorisation does not amount to a transfer of ownership.

Conversely, if the authorisation deed expressly provides for the transfer of party wall rights (e.g. "I sell you half of the wall for €1"), then it is a real estate sale subject to land registration. The Court of Cassation clarified this distinction in a judgment of 10 May 2006 (No. 05-10.534).

What this means for the future: the courts remain attached to the protection of property rights. A simple amicable agreement, even in writing, is not sufficient to create real rights. To secure a situation, it is essential to go through a notary and register the deed. This trend should strengthen with the digitisation of land registries, which makes land registration more accessible and more binding.

Checklist before acting

• Q1: Can I build a wall astride the boundary without my neighbour's agreement? No. You must obtain his written authorisation, preferably by notarial deed. Failing that, you risk an action for demolition for encroachment.
• Q2: My neighbour authorised me orally to build, is this valid? The oral agreement is valid between you, but it is very difficult to prove and will not be enforceable against a future purchaser. Have it recorded in writing.
• Q3: Can I acquire party wall rights by long use? Yes, if you have possessed the wall as owner for 30 years, without equivocation. But if you built with authorisation, this period does not run, because your possession is not as owner.
• Q4: What if my neighbour builds a wall on the boundary without my agreement? You can bring an action for boundary determination and demolition. The time limit to act is 30 years from the construction. Consult a lawyer quickly to assert your rights.
• Q5: Is a private deed sufficient to create an easement of party wall? No. An easement is a real right that must be evidenced by a notarial deed and registered. A simple private writing is not enforceable against third parties.

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

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