You buy a Paris flat with a lovely terrace created by knocking through a load-bearing wall, or you split a large apartment into two studios and add air-conditioning units to the courtyard facade. In France, none of this is a purely private matter once the building is a copropriété (co-ownership). Works that touch the common parts or change the outward appearance of the building need a vote of the general meeting, and works carried out without that vote are irregular: the co-owners’ association can go to court and obtain demolition and restoration at your expense. Three rulings of the Third Civil Chamber of the Court of Cassation, including one delivered on 19 March 2026, set the boundaries with unusual clarity: cancelling an abusive refusal is not the same as granting permission, unauthorised installations must be removed, and time limits run very differently depending on whether the works were ever authorised. This guide explains, for foreign owners, which works need a vote, what happens when the vote is skipped, and how to regularise or defend the position before the Paris courts.

I. Which works need a vote and what happens when the vote is skipped

A. The Article 25(b) majority rule for works affecting the common parts or the exterior

French apartment buildings are almost always held under the regime of the Act of 10 July 1965 on the status of co-owned buildings, the loi du 10 juillet 1965 (Co-ownership Act). Each flat is a private lot, but the structure, roof, facades, staircases, courtyards, soil and networks belong to all the co-owners together as parties communes (common parts). The dividing line matters because the owner of a flat is sovereign inside his own walls but needs collective permission as soon as his project crosses that line. Opening a load-bearing wall, cutting a slab to create a staircase or a light well, extending onto a terrace, enclosing a balcony, replacing windows with a different model, installing an external air-conditioning unit or a heat pump, creating an opening onto the street: all of these affect the common parts or the aspect extérieur de l’immeuble (outward appearance of the building) and therefore require a decision of the assemblée générale (general meeting).

The required majority is demanding. Article 25(b) of the 1965 Act provides, in a single sentence recalled word for word by the Court of Cassation when it quashed the Chambéry ruling on 30 May 2024 (official full text on courdecassation.fr), a rule that every foreign buyer should read before signing a renovation contract: « Selon ce texte, ne sont adoptées qu’à la majorité des voix de tous les copropriétaires les décisions concernant l’autorisation donnée à certains copropriétaires d’effectuer à leurs frais des travaux affectant les parties communes ou l’aspect extérieur de l’immeuble, et conformes à la destination de celui-ci. » In English: decisions authorising one or more co-owners to carry out, at their own expense, works affecting the common parts or the outward appearance of the building, consistent with the building’s intended use, pass only by a majority of the votes of all the co-owners, present or not. This is an absolute majority of the entire co-ownership, not a majority of those attending the meeting. A project approved by most of the owners in the room can still fail if too many owners are absent or abstain, which is exactly why foreign buyers who renovate from abroad, vote by proxy without instructions, or skip meetings altogether discover the problem too late.

Three cumulative conditions therefore frame every lawful project: the works must be consistent with the destination de l’immeuble (the residential, mixed or commercial character assigned to the building by its by-laws), they must be authorised by the absolute-majority vote, and they remain entirely at the expense and risk of the owner who benefits from them. The official English-language guidance of the French administration states the consequence of skipping the vote without ambiguity: works carried out without the authorisation of the general meeting are irregular, and the co-owners’ association, the syndicat des copropriétaires (syndicate of co-owners), can demand that the works stop and that what has been built be demolished, including through court proceedings (service-public.gouv.fr, works in co-owned buildings, English version). Before designing any project, the foreign owner should therefore read the règlement de copropriété (co-ownership by-laws), which may prohibit certain works outright, and check the minutes of past meetings, the procès-verbaux d’assemblée générale (general meeting minutes), to see how the building has treated similar requests. A practical overview of how French co-ownership charges and disputes work for foreign owners is also useful background when the renovation debate turns into a wider conflict with the syndic (managing agent); readers unfamiliar with the institution can consult the English-language guide to French real estate law in Paris before going further.

Two traps catch foreign buyers in particular. The first is the belief that the seller’s word, the estate agent’s assurances, or even a planning permission from the town hall replaces the co-ownership vote. It does not. Town planning consent (autorisation d’urbanisme) and co-ownership consent are two separate legal orders: the mayor checks the city, the general meeting checks the building, and either one can block the project on its own. Changing windows, creating an external opening, altering the colour of shutters or adding equipment to the facade typically needs both. The second trap is the purchase of a flat whose previous owner already carried out unauthorised works. The buyer inherits the irregularity with the keys: the syndicate’s demolition claim follows the lot, not the person who wielded the drill, and the buyer’s only recourse is then against the seller under the law of hidden defects or misrepresentation, a second lawsuit with its own evidence problems. Anyone buying in Paris should therefore ask the syndic for recent meeting minutes, compare the actual state of the flat with the by-laws’ description of the lot, and treat any discrepancy, a missing wall, an extra bathroom, a closed balcony, as a red flag to be cleared before the final deed, the acte authentique (notarial deed of sale).

B. Building first and asking later: why French courts order restoration

The leading modern statement comes from the Court of Cassation itself. In a published decision of 19 September 2012 (Third Civil Chamber, appeal no. 11-21.631, official full text on courdecassation.fr), the owners of two lots in a Nice building wanted to convert a storage unit into a flat. The general meeting of 2 October 2006 refused. The owners sued, obtained at first instance both the annulment of the refusal and permission to build, and went ahead with the works. The Aix-en-Provence Court of Appeal then held that the refusal had indeed been an abuse of the majority, but that the annulment of a refusal could not stand in for an authorisation, and it sent the project back to the sovereign general meeting while refusing to order restoration. The Court of Cassation quashed that compromise: having found that the works had been carried out before any authorisation was requested, and recalling that cancelling a decision that refuses permission is not the same as granting permission, the appeal court had violated Article 25(b) by rejecting the syndicate’s claim for restoration of the lot to its previous state. The sentence to remember is short: « que l’annulation d’une décision de refus d’autorisation de travaux ne vaut pas autorisation » In English: the annulment of a decision refusing permission for works does not amount to permission. Even an abusive refusal does not legalise works that were built first and authorised never.

Twelve years later, the same chamber confirmed that the sanction is removal, ordered if necessary under a daily penalty. In its decision of 30 May 2024 (Third Civil Chamber, appeal no. 22-23.878, official full text on courdecassation.fr), two property companies that had bought off-plan lots installed heating and air-conditioning equipment affecting the common parts without the Article 25(b) vote. Neighbouring owners sued for removal. The Chambéry Court of Appeal rejected the claim, but the Court of Cassation quashed: Article 25(b) requires the absolute-majority vote for any authorisation to carry out works affecting the common parts or the outward appearance, and the lower court could not refuse removal once it was established that the installations had been put in place without that vote. The practical lesson for a foreign owner is blunt. Air-conditioning boxes screwed to a courtyard wall, a heat pump on a balcony slab, a flue through the facade: these everyday comfort installations are exactly the kind of works judges order to be taken down, at the owner’s cost, under an astreinte (periodic penalty payment) that accumulates every day of delay until the equipment is gone.

Liability does not stop at demolition. Works carried out without care engage the general law of civil liability alongside the co-ownership regime. Article 1240 of the Civil Code states: « Tout fait quelconque de l’homme, qui cause à autrui un dommage, oblige celui par la faute duquel il est arrivé à le réparer. » In English: any act whatever of man which causes damage to another obliges him by whose fault it occurred to repair it (Article 1240, Civil Code, official Légifrance text). Cracks appearing in the neighbour’s ceiling after a wall is opened, water ingress after a terrace is waterproofed badly, a facade weakened by an unauthorised opening: the owner who ordered the works answers for the consequences, and the building owner also answers for damage caused by the ruin of his building where poor maintenance or a construction defect is involved (Article 1244, Civil Code, official Légifrance text). Neighbours have a further, independent weapon that survives even a perfectly regular vote: the law of abnormal neighbourhood disturbance, now codified, which obliges owners, tenants, occupiers and project owners to repair abnormal disturbance caused to neighbours regardless of fault (Article 1253, Civil Code, official Légifrance text). An authorisation from the general meeting protects against the syndicate’s demolition claim; it never immunises the owner against a neighbour’s claim for noise, loss of light, vibration or water damage. And on evidence, the burden follows the classic rule: « Celui qui réclame l’exécution d’une obligation doit la prouver. » In English: a party who claims performance of an obligation must prove it (Article 1353, Civil Code, official Légifrance text). The syndicate must prove the absence of a vote and the interference with the common parts; the owner who pleads an old authorisation must produce the meeting minutes that record it. Paper wins these cases far more often than rhetoric.

II. How to save, regularise or defend the works once they are challenged

A. Ratification, limitation periods and the ten-year trap clarified in March 2026

Not every irregularity ends in demolition, but every rescue route runs through the general meeting or the court, never through inertia. The first route is ratification (subsequent approval): the owner places the works, as built, on the agenda of the next general meeting and asks the co-owners to approve them retrospectively by the same Article 25(b) absolute majority. Judges accept that irregular works started without prior permission can be ratified by a later decision, and a ratification regularly voted extinguishes the syndicate’s demolition claim for the future. Success depends on presentation. A file with architect’s plans, a structural engineer’s certificate confirming that the building’s solidity is untouched, photographs, proof of identical works already tolerated in the building, and a written commitment to bear all costs and restore the surroundings gives the meeting reasons to say yes. A bare oral request from an absent owner, relayed by an uninstructed proxy, almost always fails. Foreign owners should attend in person or give a precise written proxy to someone who will defend the file, and should have the draft resolution, the projet de résolution (draft resolution), worded by a lawyer so that the vote, if won, covers exactly what was built, no more and no less.

The second route is time, but it is a trap for the unwary in both directions. The Co-ownership Act gives personal actions between co-owners, or between a co-owner and the syndicate, a ten-year limitation period: « les actions personnelles nées de l’application de la présente loi entre des copropriétaires, ou entre un copropriétaire et le syndicat, se prescrivent par un délai de dix ans. » In English: personal actions arising from the application of the Act, between co-owners or between a co-owner and the syndicate, are time-barred after ten years. The decision of 19 March 2026 (Third Civil Chamber, appeal no. 24-18.919, official full text on courdecassation.fr) shows how decisive the starting characterisation is. A property company had converted a ground-floor shop into a porch giving access to a rear building, with openings cut into the front and rear facades in 1992 and 1993. The syndicate sued for restoration only on 30 May 2022, thirty years later. The Rennes Court of Appeal first had to decide a prior question: had the extraordinary general meeting of 9 April 1992 authorised the works? It found that it had. From that finding everything followed: because the works had been authorised, the syndicate’s restoration claim was a personal action subject to the ten-year period, and a claim filed in 2022 for works completed in 1992–1993 was time-barred. The Court of Cassation approved the reasoning on the prior question and, ruling on the merits without remand, confirmed that the syndicate’s action was prescribed.

Foreign owners must read this ruling the right way round. It does not say that ten quiet years legalise unauthorised works. It says that the legal nature of the syndicate’s claim, and therefore the applicable time limit, depends on whether an authorisation ever existed: authorised works generate a personal action with a ten-year clock, while works carried out with no vote at all leave the owner exposed to a claim anchored in the collective ownership of the common parts, which courts analyse far less indulgently. In practice, an owner who cannot produce the minutes of an authorising vote should never assume that the passage of time protects him; the syndicate that discovers an old opening, an old encroachment, an old extension will first argue that nothing was ever voted, and the owner will then bear the burden of proving the contrary with thirty-year-old paper. Conversely, a syndicate that sat on its rights for decades after duly authorising works, as in the 2026 case, will find its claim dismissed as out of time. Ordinary damages claims between neighbours, finally, follow the general five-year period for personal and movable actions, running from the day the holder knew or should have known the facts (Article 2224, Civil Code, official Légifrance text), which is why a neighbour who notices cracks should have them recorded by a court officer immediately rather than waiting for the next family visit to Paris.

B. A foreign owner’s practical file: evidence, urgent proceedings and Paris specifics

Whether the works are a future project or an existing dispute, the file is built the same way, and distance makes methodical paper even more important. First, establish the baseline: obtain the full règlement de copropriété with its descriptive schedule of the lots, the last three years of general meeting minutes, the building’s maintenance log, the carnet d’entretien (maintenance record), and any prior authorisations concerning the same lot. Second, freeze the facts: dated photographs, a report by a commissaire de justice (court officer, formerly huissier de justice) describing the works and their effects on the common parts, and where structure is involved, an independent engineer’s opinion. Third, quantify: itemised quotes for restoration to the previous state alongside quotes for compliant completion, because negotiation with the syndicate, like litigation, turns on numbers. Fourth, check the diary: when were the works finished, when did the syndicate demonstrably learn of them, was any vote held, and which limitation clock is plausibly running. A buyer discovering pre-existing unauthorised works after completion of the sale should also preserve everything against the seller: the listing, the preliminary contract, the technical survey file, and any written statement that the flat was sold free of alterations, since the price reduction or annulment claim against the seller is a separate action with its own short deadlines.

Procedure in Paris has its own geography that foreign owners should know. Demolition and restoration claims go to the tribunal judiciaire (ordinary civil court) of the place where the building stands, which for a Paris flat is the Paris court, where the eighth chamber handles co-ownership litigation day in and day out. Where works are ongoing, the syndicate does not have to wait for a full trial: it can apply to the urgent-applications judge, the juge des référés (interim relief judge), for an order stopping the works and prohibiting their continuation under penalty, and Paris judges grant such orders routinely when the absence of a vote is plain on the papers. A Paris interim order of July 2026, identified in the case-law search for this guide, follows exactly that pattern. The owner who receives a formal demand, a mise en demeure (formal notice), from the syndic should therefore treat the timetable as counted in weeks, not seasons: instruct a lawyer, suspend the disputed works, request an extraordinary general meeting to seek ratification, and prepare the evidence file described above. Continuing to build after a formal notice, while hoping that a future meeting will forgive everything, is the single behaviour that turns a negotiable irregularity into a certain demolition order with costs and penalties.

Three practical points specific to non-resident owners deserve emphasis. First, service of documents: court papers served on an owner domiciled abroad follow international service channels and extend procedural timetables, but they do not prevent the case from moving forward, and default judgments are enforceable against the Paris flat itself. Electing domicile with a Paris lawyer (élection de domicile, elected address for service) keeps the owner informed in real time and avoids learning of a demolition order from the tenant. Second, insurance and financing: standard multi-risk home insurance does not cover demolition ordered for unauthorised works, and a lender financing the renovation may treat the absence of the co-ownership vote as a breach of the loan’s conditions, so both policies should be checked before the first hammer blow. Third, taxation is noted but not detailed here: restoration costs and penalties are not part of the acquisition price and do not improve the property’s tax base the way compliant improvement works can; owners with cross-border tax positions should take separate advice rather than assume that money spent under a court order counts as investment. Throughout, the relationship with the building matters as much as the law: a syndic and neighbours who receive plans, guarantees and a timetable before the works start vote differently from a meeting that discovers a finished fait accompli, and the Paris Bar’s real-estate practitioners confirm that most ratification files succeed or fail on that human difference. Readers who need an English-speaking point of contact for the whole file, from the meeting strategy to the courtroom, can turn to the Paris real-estate team presenting its practice in English.

Conclusion

Unauthorised works in a French copropriété are not a minor administrative oversight; they are an attack on collectively owned property that the syndicate can have demolished at the owner’s expense. The rule of Article 25(b) is mechanical: no absolute-majority vote, no lawful works affecting the common parts or the outward appearance. The Court of Cassation has closed the three escape routes owners most often imagine: an abusive refusal, once annulled, still does not authorise anything, as held in 2012; equipment installed without a vote must be removed, as held in 2024; and limitation periods protect only the owner who can prove that a vote once existed, as clarified in March 2026. For the foreign owner, the method follows directly: verify the by-laws and the minutes before buying or building, obtain the vote before the works, seek ratification at the first sign of conflict, freeze evidence with a court officer, and move fast once the syndic writes. Handled that way, most files end in a voted regularisation rather than a demolition crew; handled the other way, they end exactly where the three rulings say they end, with the building restored and the bill sent to the owner who built without asking.