Raising a building in co-ownership: who holds the right to build upwards?

Raising a building in co-ownership: who holds the right to build upwards?

Urban densification and the statutory encouragement of building upwards, reinforced by the recent regulations implementing the recommendations of the Rivaton report (Decree No. 2026-200 and the Order of 18 March 2026), make adding storeys (surélévation) a strategic means of increasing property value. But a preliminary question, often overlooked, governs any such operation: who actually holds the right to add storeys where the building includes special common parts?

In a judgment intended for publication in the Bulletin (Cour de cassation, 3rd Civil Chamber, 2 April 2026, No. 24-15.059, FS-B), the Third Civil Chamber of the Cour de cassation gives a ruling of principle: where the co-ownership rules (règlement de copropriété) are silent, that right belongs to the co-ownership association (syndicat des copropriétaires), even where the building is burdened with special common parts.

The legal framework: a right presumed to be common but capable of adjustment

The presumption in Article 3 of the Law of 10 July 1965

Article 3 of Law No. 65-557 of 10 July 1965 defines as common those parts intended for the use or benefit of all the co-owners, or of several of them. It also deems "rights accessory to the common parts" to include the right to raise a building intended for common use or comprising several private lots. The transfer of that right is governed by Article 35 of the same law (in the version resulting from the ALUR Law No. 2014-366 of 24 March 2014, prior to that resulting from Order No. 2019-1101 of 30 October 2019).

A default presumption of intent

These presumptions are not matters of public policy: they apply "in the silence or contradiction of the title deeds". The co-owners remain entirely free to depart from the statutory classification in the co-ownership rules. The mandatory content of those rules, the regime of clauses deemed unwritten and their enforceability against third parties are covered in our article on the co-ownership rules.

Case law has accepted, for example, that a roof may be classified as a private lot where the rules expressly so provide, the right to build then becoming an accessory of the private parts (Cour de cassation, 3rd Civil Chamber, 18 October 2018, No. 17-23.019). Conversely, the right to raise a building is presumed to be an accessory of the common parts only in the absence of a contrary provision (Cour de cassation, 3rd Civil Chamber, 11 June 2014, No. 13-17.121).

The contribution of the judgment of 2 April 2026: strict interpretation of exceptions

A novel question: general common parts versus special common parts

The originality of the judgment lies in the ground chosen. Until now, the debate classically opposed common parts and private parts. The Third Civil Chamber here transposes that analytical framework to a different dichotomy: that of general common parts and special common parts.

In this case, the co-ownership rules classified certain parts of Building D as special common parts and listed the right to add storeys, in general terms, among the accessories of the common parts. But the list of special common parts specific to Buildings A, B, C and D mentioned only physical accessories, not accessory rights.

A strict application of the principles of interpretation

The Cour de cassation, true to the maxim exceptio est strictissimae interpretationis, refuses to extend the scope of the special common parts by way of interpretation. It holds that, absent an express provision including the right to raise the building among the special common parts, that right falls within the general common parts and belongs to the co-ownership association.

The rule is consistent with the case law on ambiguous or contradictory clauses (Cour de cassation, 3rd Civil Chamber, 6 February 2020, No. 18-18.825; Cour de cassation, 3rd Civil Chamber, 16 October 2013, No. 12-23.252): in case of doubt, the general principle prevails over the exception.

Practical consequences for those involved in co-ownership

For the co-ownership association

The association retains control of the right to add storeys and, accordingly, of its transfer to a developer or of the decision to undertake works. Under Article 35 of the 1965 Law, the decision to dispose of the right or to carry out the works rests with the general meeting, by the required majority.

For the co-owners of a building with special common parts

Maintaining a special organisation within a building is not sufficient to give the co-owners concerned exclusive control of the right to add storeys. Any operation will require the association's agreement. The proceeds of the transfer will be shared among all the co-owners, in accordance with the applicable statutory and contractual rules of allocation.

For operators (developers, investors, property dealers)

A rigorous reading of the co-ownership rules is required before any negotiation. Wrongly identifying the holder of the right may undermine the legal certainty of the operation and expose it to proceedings for nullity.

Identified litigation risks

1. Challenge to the general meeting's decision by a co-owner who considers that the decision should have been taken only by the holders of the special common parts.
2. Annulment of a transfer agreed by a sub-group of co-owners lacking authority to dispose of the right.
3. Disputes over the transfer price, in particular over the share allocated to each co-owner.
4. Disputes over the execution of the works affecting the common parts (liability of the association, abnormal neighbourhood disturbance).
5. Liability of the property manager (syndic) or of the co-ownership council for failing to give the right a correct legal classification.

Strategies and recommendations

Audit the co-ownership rules beforehand

Any operation to add storeys, whether contemplated by the association or by a third-party developer, must be preceded by an exhaustive analysis of the rules and of the schedule of division of the building (état descriptif de division). The classification of the right to add storeys must be sought not only in the general list of common parts, but also in the clauses dealing with special common parts. The discrepancies between the schedule of division and the rules, and their effect on whether a lot can be used, are analysed in our article on those two documents.

Secure the decision through express drafting

If an exclusive allocation of the right to add storeys to the co-owners of a building is desired, it must be drafted unambiguously in the co-ownership rules. An amendment to the rules may be contemplated by the majority required under Article 26 of the 1965 Law. The majorities applicable depending on the clause concerned are set out in our article on the cases in which unanimity is required to amend the co-ownership rules.

Anticipate litigation

The general meeting's decision approving a transfer or authorising works to add storeys must be notified in accordance with Article 42 of the 1965 Law, with particular care given to traceability (electronic or postal notification, proof of delivery), so that the two-month period for challenge begins to run.

Conclusion: drafting rigour as a condition of any operation to add storeys

The judgment of 2 April 2026 sends a clear signal: increasing value through operations to add storeys requires a demanding reading of the co-ownership rules. Absent an express clause, it is the association, and the association alone, that holds the right to raise the building.

For co-ownerships pursuing a densification strategy, as for operators negotiating the acquisition of a right to add storeys, a prior legal audit is no longer optional: it is a condition of the operation's legal certainty.

‍