A flat sold with a toilet on the landing and a maid’s room two floors up, with a certified floor area of 60.07 m². Do these rooms count, and is the surveyor who overstated the area answerable to the buyer? On 5 March 2026, the Third Civil Chamber of the Cour de cassation (the French supreme court for civil and commercial matters) upheld the inclusion of these rooms in the Carrez area and quashed the decision clearing the surveyor of any fault.
The facts
By a deed of 25 April 2017, sellers sold to buyers, for €270,000, lot no. 10 of a co-owned building (copropriété): a third-floor flat, with a WC on the landing, a maid’s room on the fifth floor and a cellar. The sellers declared a floor area of 60.07 m², in line with the measurement certificate drawn up by a surveyor (diagnostiqueur, the certified technician who prepares pre-sale reports).
The buyers sued the sellers and the surveyor for a price reduction and damages. From the surveyor, they claimed compensation for a lost chance of higher rental income and for an extra cost of credit.
On 12 January 2023 the Versailles Court of Appeal dismissed the claim against the sellers for a partial refund of the price: it included the WC and the maid’s room in the measurement, and held that the area that should have been measured and stated in the deed was 59 m². It also dismissed the claims against the surveyor, holding that the surveyor “does not have to know which premises do or do not form a lot under the terms of the co-ownership regulations” (règlement de copropriété; translated from the French).
The buyers appealed: in their view, these rooms, which had no direct access to the flat, fell under the rule excluding lots or parts of lots under 8 m² (article 4-2 of the decree of 17 March 1967), and the surveyor had to apply the rules of the loi Carrez (article 46 of the law of 10 July 1965) to the physical state of the property.
The decision
In its ruling (Cass. 3e civ., 5 March 2026, appeal no. 23-13.288, unreported), the Cour de cassation dismissed the first ground of appeal, on the floor area, and quashed in part on the second, on the surveyor: the quashing covers only the dismissal of the claims against it, the costs, and the order for the buyers to pay it €2,500 in frais irrépétibles (legal expenses other than court costs).
On the floor area, the Court of Appeal had found that the WC and the maid’s room “did not form lots separate from the flat but were merely detached rooms of it forming part, under the terms of the co-ownership regulations, of the same lot, which had never been divided into fractions”. The Court held that it “correctly deduced from this that the area of these premises, which were not subject to any statutory or regulatory exclusion from the scope of article 46 of the law of 10 July 1965, had to be taken into account in calculating the area of the private parts sold”. The claim against the sellers therefore failed, and they were released from the proceedings.
On the surveyor, under article 1240 of the Civil Code, the basis of liability for fault, the Court quashed: “By so ruling, when it found that the surveyor had issued a measurement certificate certifying a private area of lot no. 10 of 60.07 m² and held that the area of the lot sold that should have been measured and stated in the deed was 59 m², the Court of Appeal, which relied on grounds ineffective to rule out any fault on the part of the surveyor, breached the above-mentioned text.”
The case was sent back to the Versailles Court of Appeal, differently composed. The Court did not rule on the losses claimed, nor on the extent of the checks the surveyor must make in the co-ownership regulations: given the gap found, the reasoning based on those regulations was ineffective.
What this changes for valuation
The composition of the lot is read before measuring. The area survey starts from the deed and the co-ownership regulations, then is checked against the property’s physical state. The texts exclude cellars, garages and parking spaces, as well as lots or parts of lots under 8 m² (article 46 of the law of 10 July 1965, article 4-2 of the decree of 17 March 1967); the area is calculated net of walls, partitions, steps, stairwells, ducts and embrasures, leaving out parts under 1.80 m high (article 4-1 of the same decree; Charte de l’expertise en évaluation immobilière, the French property valuation charter, 6th edition, November 2025, Title III, § 3.3.5). In the reasoning approved by the Court, a detached room of a never-divided lot is neither a lot nor part of one: the 8 m² threshold does not exclude it, and it counts.
Two claims, two measures. Against the seller, article 46 of the law of 10 July 1965 allows a proportional price reduction when the actual area is more than one twentieth below that stated in the deed. The gap of 1.07 m² is about 1.8% of the declared area, below the one-twentieth threshold: the claim against the sellers could not succeed. Against the surveyor, the ground is article 1240, which requires a fault, a loss and a causal link; the Court quashed the dismissal of the claims even though the gap does not exceed one twentieth. A floor area shortfall claimed by the client who commissioned the building (maître de l’ouvrage) from its architect follows another, contractual logic, discussed separately.
The pro rata is not the loss. As a benchmark, €270,000 for 60.07 m² gives about €4,495 per square metre, or about €4,810 for 1.07 m². That calculation measures neither a loss of rent nor an extra cost of credit. The report establishes the rental and market value of the lot as it is and as the certificate described it, by comparison, weighting the areas: a maid’s room on the fifth floor and a toilet on the landing do not have the square metre value of the main rooms (Charte, Title III, chapter 4).
Each survey has its own regime. For asbestos and termites, the survey guarantees the buyer against the risk and the loss is certain. For an energy performance certificate (DPE) for a sale before 1 July 2021, then merely informative, the Court allows a lost chance to negotiate the price. For the Carrez measurement, the ruling rests on article 1240 without characterising the loss: the report states whether it quantifies an actual loss or a lost chance, and presents both amounts.
What the valuer takes from it
- The survey starts from the legal composition of the lot: a detached room of a never-divided lot counts towards the Carrez area, unless a statutory or regulatory exclusion applies.
- Below one twentieth, there is no price reduction against the seller; the Court nevertheless quashed the dismissal of the claims against the surveyor.
- The loss claimed from the surveyor is quantified in value and in rent, by comparison, not by a rule of three on the price.
- Secondary areas are weighted before being valued.
Further reading
The Property loss of value page presents the assignment. The guide I paid too much for my French house: can I challenge the price? and the glossary entries Carrez floor area, weighted floor area and property loss complement this article. Between client and architect: Missing floor area: the architect must see the plans are followed. On the same theme: Incorrect energy certificate: lost chance to negotiate the price and Asbestos or termites missed: the surveyor owes the full loss. The decision is available on Légifrance.
What next
The certified floor area does not match the lot you bought?
I go back over the composition of the lot and its floor areas, then I quantify what the gap with the certificate means in value and in rent, room by room. The report relies on verifiable references per square metre that your lawyer can produce.
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