You bought a 62-square-metre apartment in Paris, and eighteen months later a new measurement says it is only 57 square metres. In France, that five-square-metre gap is not a mere disappointment: it can be worth tens of thousands of euros. French law gives the buyer of a co-ownership lot a specific, powerful remedy when the real private area falls short of the area stated in the deed. It is called the loi Carrez (Carrez-area) action, after the 1996 statute that created it, and it is one of the most concrete buyer-protection tools in French conveyancing. But it is fenced in by strict measurement rules, a tolerance threshold and a short forfeiture deadline that foreign buyers regularly miss.

This guide explains, for non-resident and expatriate buyers, what area the seller must state, how that area must be measured, and how to act when the flat turns out to be smaller than promised. It covers both resales and off-plan purchases, the two court actions available, and the practical question of who ultimately bears the cost. The figures and procedures below reflect the law as in force in September 2026 and the published case law of the Cour de cassation (France’s supreme civil court).

I. The Area the Seller Must State and How It Must Be Measured

Every sale of a co-ownership lot in France must state a number: the private area of the lot, measured according to public rules. That number appears first in the preliminary contract and again in the notarial deed of sale, and the buyer can rely on it. Understanding where the number comes from is the starting point of any claim.

A. A Mandatory Area Statement in Every Preliminary Contract and Deed

Article 46 of the Law of 10 July 1965 on co-ownership requires that every promesse de vente (unilateral promise of sale), every preliminary agreement and every deed transferring a co-ownership lot state the private area of that lot. The rule covers resales as well as off-plan sales, and it applies lot by lot. Cellars, garages and parking spaces are excluded from the duty, as are lots below a small size threshold set by regulation. The statement is normally supplied by a professional survey report, the certificat de mesurage (measurement certificate), commissioned before signature and attached to the file passed to the notaire (public notary conveyancer).

For a foreign buyer, three practical points matter at this stage. First, the area in the deed is a legal statement, not marketing material: the seller is bound by it, even if the figure came from a surveyor the seller hired. Second, the preliminary contract, usually a compromis de vente (preliminary sale agreement), already contains the figure, so the buyer should compare it with the draft deed and with any floor plans rather than discovering a discrepancy at the signing table. Third, the measurement standard is French public law, not the American, British or Middle Eastern notion of floor area: balconies, terraces, ceiling height and wall thicknesses are treated in specific ways that surprise many international buyers, as explained below. A flat honestly described as 60 square metres under a foreign standard can lawfully be stated at a lower figure in France, and only a shortfall against the French-law figure opens a remedy.

In practice the figure comes from a diagnostiqueur (certified property surveyor) who visits the flat with a laser measure and issues the certificat de mesurage (measurement certificate) that the estate agent circulates and the notary files. These certificates are quick, inexpensive documents, often produced the same week as the listing, and their quality varies enormously: sloped ceilings approximated rather than measured, loggias classified by habit, partition thicknesses guessed. The certificate binds the seller vis-à-vis the buyer, not the surveyor vis-à-vis the buyer, which is why the buyer’s remedy runs against the vendor even when everyone agrees the surveyor made the mistake. Foreign buyers should also know that the certificate has no legal monopoly attached to it: any competent professional can re-measure, and courts routinely prefer a careful contradictory report over the original certificate. A re-measurement commissioned from a géomètre-expert (licensed surveyor) with the seller invited to attend therefore serves two purposes at once, proving the shortfall and neutralising the argument that the buyer’s expert measured alone and self-servingly.

Where the seller omits the area statement altogether, the sanction is severe: the buyer may sue for annulment of the agreement. The statute provides that the nullity action can be brought within one month of the notarial deed of sale: “Le bénéficiaire en cas de promesse de vente, le promettant en cas de promesse d’achat ou l’acquéreur peut intenter l’action en nullité, au plus tard à l’expiration d’un délai d’un mois à compter de l’acte authentique constatant la réalisation de la vente.” (Article 46 of the Law of 10 July 1965). In plain English: the buyer, or the beneficiary of a sale promise, may bring the nullity action no later than one month after the notarial deed recording the sale. And the Cour de cassation has held that this right survives as long as no compliant deed has cured it: “seule la signature de l’acte authentique constatant la réalisation de la vente mentionnant la superficie de la partie privative du lot ou de la fraction de lot entraîne la déchéance du droit à engager ou à poursuivre une action en nullité de la promesse ou du contrat qui l’a précédée, fondée sur l’absence de mention de cette superficie” (Cass., 3rd Civil Chamber, 22 November 2018, No. 17-23.366). In other words, only the signature of a notarial deed that actually states the private area extinguishes the right to pursue nullity based on the missing statement. A seller who hands over a measurement certificate informally, outside the deed, does not cure the defect.

B. How Surveyors Must Measure: Walls Deducted, Low Ceilings Ignored, Small Lots Excluded

The substantive measurement rule sits in Article 4-1 of the Decree of 17 March 1967. The private area is the floor area of enclosed, covered premises, after deducting the surfaces taken up by walls, partitions, steps, stairwells, ducts and door and window recesses. Critically for Paris attics, converted maid’s rooms and duplexes: “Il n’est pas tenu compte des planchers des parties des locaux d’une hauteur inférieure à 1,80 mètre.” (Article 4-1 of the Decree of 17 March 1967). In English: no account is taken of floor areas where the ceiling height is below 1.80 metres. A charming mansarded bedroom therefore contributes only its portion above that height, however usable the lower part feels.

Two further refinements complete the picture. Article 4-2 of the same decree provides: “Les lots ou fractions de lots d’une superficie inférieure à 8 mètres carrés ne sont pas pris en compte pour le calcul de la superficie mentionnée à l’article 4-1.” (Article 4-2 of the Decree of 17 March 1967). In English: lots or fractions of lots under 8 square metres are simply left out of the stated area. And the courts decide borderline cases functionally, not formally. In a leading ruling, buyers argued that two private loggias of 6.27 and 6.69 square metres should have been excluded under the 8-square-metre rule; the Cour de cassation upheld the court of appeal, holding that “en a déduit à bon droit que ces loggias devaient être prises en compte pour le calcul de la superficie des parties privatives vendues” (Cass., 3rd Civil Chamber, 28 January 2015, No. 13-26.035). In English: the court of appeal rightly concluded that these loggias had to be included in the private area, because it had found them enclosed and habitable at the date of sale. An enclosed, habitable loggia counts even below eight square metres; an open balcony or terrace does not.

Off-plan purchases follow a sibling but distinct regime. In a vente en l’état futur d’achèvement (off-plan sale), the contract states an approximate habitable area, and the Cour de cassation confirmed in 2021 that this means habitable area in the technical sense of the Construction Code: “Le dernier de ces textes définit la surface habitable d’un bâtiment d’habitation comme la surface de plancher construite, après déduction des surfaces occupées par les murs, cloisons, marches et cages d’escaliers, gaines, embrasures de portes et de fenêtres” (Cass., 3rd Civil Chamber, 18 March 2021, No. 19-24.994). In English: the habitable area of a dwelling is the constructed floor area minus walls, partitions, steps, stairwells, ducts and door and window recesses, with attics, cellars, garages, terraces, loggias and balconies left out. Foreign buyers of new-build flats should therefore expect the off-plan figure to exclude outdoor spaces entirely, and should compare the contractual area with the post-completion measurement on that basis. OurCabinet’s Paris real estate team regularly sees disputes where a buyer counted a large terrace as living space and the developer lawfully did not.

II. Acting on a Shortfall: Price Reduction or Nullity, Within Strict Deadlines

Once a re-measurement shows a gap, French law offers two actions with very different logics: keep the property and recover the overpaid portion of the price, or attack the contract itself. Both are subject to forfeiture deadlines counted from the notarial deed, and both turn on proof by a contradictory, professional measurement.

A. Two Remedies, Two Forfeiture Deadlines

The workhorse remedy is the price-reduction action. Where the real area is more than one-twentieth below the stated area, the buyer can force the seller to reduce the price proportionally: “Si la superficie est inférieure de plus d’un vingtième à celle exprimée dans l’acte, le vendeur, à la demande de l’acquéreur, supporte une diminution du prix proportionnelle à la moindre mesure.” (Article 46 of the Law of 10 July 1965). In English: if the area is more than one-twentieth below the figure in the deed, the seller must bear a price reduction proportional to the shortfall, at the buyer’s request. Three features deserve emphasis. First, the tolerance is one-twentieth, i.e. five per cent: a stated 60 square metres must in reality measure below 57 square metres before any claim arises; a 58.5-square-metre reality gives no action. Second, the reduction is strictly proportional to the missing area applied to the price: on a 600,000 euro purchase stated at 60 square metres but really 56, the reduction is 4/60ths of the price, or 40,000 euros, a calculation courts perform without any need to prove a separate loss. Third, an excess in the buyer’s favour creates no supplement: if the flat is bigger than stated, the seller cannot claim a penny more.

The price-reduction action must be brought within one year of the notarial deed, on pain of forfeiture: “L’action en diminution du prix doit être intentée par l’acquéreur dans un délai d’un an à compter de l’acte authentique constatant la réalisation de la vente, à peine de déchéance.” (Article 46 of the Law of 10 July 1965). In English: the buyer must bring the price-reduction action within one year of the notarial deed recording the sale, failing which the right is lost. This is a délai de forclusion (forfeiture deadline), stricter than an ordinary limitation period: courts cannot extend it for fairness, and missing it ends the claim even if the shortfall is blatant. Foreign owners who let the file sleep while renting out the flat, waiting for a convenient trip to Paris, lose everything at the anniversary date of the deed.

Two published rulings soften the edges of that harsh deadline without removing it. The Mixed Chamber of the Cour de cassation held that filing in time before the wrong court still preserves the action: “la citation en justice donnée même devant un juge incompétent interrompt la prescription” (Cass., Mixed Chamber, 24 November 2006, No. 04-18.610). In English: a writ issued even before a court without jurisdiction interrupts the time limit, a general principle the court expressly applied to the Article 46 one-year period. A buyer who sues promptly but in the wrong forum can therefore re-file correctly; a buyer who does nothing for a year cannot. Separately, the nullity action for a missing area statement, described in Part I, runs on its own one-month clock from the deed, but survives until a compliant deed cures the omission, as the 2018 ruling confirms. In practice, buyers cumulate: nullity where no area was ever stated, price reduction where a stated area proves overstated by more than five per cent.

B. Proof, Procedure and Who Ultimately Pays

Proof is everything, and French courts expect a professional, contradictory measurement. The buyer’s first step is to commission an independent surveyor or géomètre-expert (licensed surveyor) to re-measure strictly under Articles 4-1 and 4-2, ideally inviting the seller to attend so the report is genuinely adversarial. A tape-measure estimate by the buyer, or a foreign-style gross-area computation, carries no weight. The re-measurement should identify, room by room, the deductions applied: wall thicknesses, sub-1.80-metre zones, excluded balconies and terraces, and any sub-8-square-metre fractions. Where the gap exceeds the one-twentieth threshold, the buyer sends a formal demand to the seller, usually by bailiff’s letter or registered letter drafted by counsel, quantifying the proportional reduction and setting a payment deadline. Most files settle at this stage, because the calculation is mechanical and the case law settled.

The formal demand itself deserves care. It should identify the deed and its stated area, attach the contradictory re-measurement, show the arithmetic step by step with the one-twentieth threshold verified, state the exact proportional sum claimed, and give the seller a clear deadline, typically fifteen to thirty days, before court proceedings. Sending it by commissaire de justice, the reformed title of the French bailiff, gives a certified date and often concentrates the seller’s mind more than an ordinary letter. Sellers frequently counter with three arguments, all usually answerable on the papers: that the buyer’s expert misclassified a loggia or a sub-ceiling zone, which the room-by-room schedule rebuts; that the shortfall falls within the five-per-cent tolerance, which the arithmetic rebuts; and that too much time has passed, which the deed date and the filing receipt rebut. Where the seller offers a discounted settlement, buyers should weigh the net recovery after their own costs against the realistic timetable of a Paris court case, and should never sign a settlement that waives recourse against third parties without advice, since the surveyor’s or agent’s contribution may still be worth pursuing separately.

If the seller refuses, the action goes before the tribunal judiciaire (civil court) of the place where the property sits, which for Paris purchases means Paris. Costs follow the usual French pattern: each side bears its own lawyer’s fees in principle, the loser pays court costs, and the court may order the loser to contribute to the winner’s counsel fees under Article 700 of the Code of Civil Procedure. Expert-measurement fees, typically a few hundred to around one thousand euros in Paris, are routinely shifted to the losing seller as part of the costs. Buyers should budget eighteen to thirty months for a contested first-instance case in Paris, though interim relief is rarely needed since the buyer already owns and occupies the flat.

The seller who pays the reduction often looks for someone else to foot the bill, and here the Cour de cassation has drawn a firm line around notaries and estate agents. Where a sale was annulled and the seller had to refund the price, the court quashed a decision making the notary and the agency guarantee that refund: “en cas d’annulation de la vente, la restitution du prix perçu à laquelle le vendeur est condamné, en contrepartie de la restitution de la chose par l’acquéreur, ne constitue pas un préjudice indemnisable” (Cass., 3rd Civil Chamber, 3 May 2018, No. 17-11.132). In English: when a sale is annulled, the refund of the price the seller is ordered to pay, matched by return of the property, is not a compensable loss. The lesson for buyers: a professional’s faulty advice does not automatically convert the price mechanics into damages, and any recourse against the surveyor who produced the wrong certificate, the agent who relayed it or the notary who recorded it must be built on a distinct proven fault and a distinct loss, such as wasted financing costs or the lost opportunity to negotiate. Such recourse actions run under ordinary negligence and limitation rules, not under Article 46, and should be pleaded in the alternative from the start rather than bolted on years later.

Three traps specific to international buyers close this section. First, calendar the one-year deadline from the date of the notarial deed, not from discovery of the shortfall: French law starts the clock at signature, and a buyer who discovers the gap in month thirteen has no Article 46 action left, whatever the size of the error. Second, purchases through a French société civile immobilière (property-holding company) change nothing about the deadline but require the company, as owner, to be the claimant; ensure the company exists, is registered and can validly instruct counsel before the year expires. Third, off-plan buyers must distinguish the Carrez price-reduction action, for resale lots under Article 46, from the contractual surface-tolerance clauses and the habitable-area case law that govern new builds: the five-per-cent threshold is a creature of Article 46, while a VEFA contract may set its own tolerance band that the courts enforce as written. Readers facing a new-build shortfall should have the reservation and delivery paperwork reviewed against the 2021 habitable-area ruling before choosing their procedural vehicle. Our Paris real estate lawyers handle both tracks and can usually tell from the deed and the measurement report alone which one applies.

Conclusion

The Loi Carrez mechanism is unusually buyer-friendly: a mechanical calculation, no need to prove fraud or loss, and a line of published Cour de cassation rulings that leaves sellers little room to argue once a compliant re-measurement shows a shortfall beyond one-twentieth. Its severity runs the other way too. The one-year forfeiture deadline is absolute, the measurement standard is technical and unforgiving, and professionals answer only for their own proven faults. For a foreign buyer, the winning sequence is simple and time-sensitive: verify the stated area against the French-law standard before signing, keep the deed date diarised, commission a contradictory professional re-measurement at the first doubt, and put the seller on formal notice well before the anniversary. A five-square-metre error on a Paris purchase routinely represents several tens of thousands of euros; treating the area figure as a contractual promise rather than an estimate is the difference between recovering it and losing it forever.

Need a quick opinion on your case

If your Paris apartment measures smaller than your deed states, you can book a telephone consultation within 48 hours for an initial review of your measurement report, your deadline and your chances of a price reduction. The first consultation is billed at 80 EUR incl. VAT. Call +33 6 46 60 58 22 or write via our contact page with your deed and any survey attached.