A house is sold in 2014 with, in the basement, a room the sellers converted into a living room: insulation, partitions, tiling, a clad ceiling. Damp appears. After a court-ordered appraisal, the buyers claim 72,000 € for the works, as their main claim and whatever the legal basis, 15,000 € as a partial refund of the price in the alternative, and 10,000 € for loss of enjoyment. The Riom Court of Appeal finds a hidden defect, awards the partial refund and the loss of enjoyment, and rejects the works. On 22 January 2026 the Cour de cassation (the French supreme court for civil matters) quashed that ruling: by ruling on the alternative claim without examining the main one, the court inverted the order of the claims. Between 72,000 € and 15,000 €, the gap says everything about the difference between the cost of repairing and the loss of value.
The facts
By deed of 8 July 2014 a couple buy a house. Noticing damp in a basement room the sellers had converted into a living room, the buyers obtain the appointment of a court expert, who files his report on 12 March 2019. They then sue the sellers for the cost of repairs, a partial refund of the price and damages for loss of enjoyment, relying in particular on the builders’ ten-year warranty and on the hidden defects warranty.
The Riom Court of Appeal, on 12 September 2023, holds that the sellers’ works, “partitioning and insulating the walls, laying tiles and cladding the ceiling”, do not amount to a structure within the meaning of article 1792 of the Civil Code, finds the sellers liable under the hidden defects warranty, awards a sum as a partial refund of the price and for loss of enjoyment, and rejects the claim for the cost of works.
The decision
The third civil chamber (Cass. 3e civ., 22 January 2026, no. 24-12.809) first approves the classification: the Court of Appeal “could infer that they did not constitute a structure within the meaning of article 1792 of the Civil Code”. No ten-year warranty for a fit-out of that kind.
It then quashes, under article 4 of the Code of Civil Procedure, by which “the subject matter of the dispute is determined by the parties’ respective claims”: the buyers sought, “as their main claim, whatever the basis retained for their claims, an order that the sellers pay a sum corresponding to the cost of remedial works and, only in the alternative, a sum as a partial refund of the sale price”; by awarding the partial refund without ruling on the works, “the Court of Appeal, which inverted the order of the claims, disregarded the above provision”. Quashing limited to the rejection of the 72,000 €, remittal to the Lyon Court of Appeal.
What this changes for valuation
Three figures that do not substitute for one another. The cost of works repairs the property; the partial refund of the price corrects the sale; the loss of enjoyment compensates the time spent unable to use the room. The first is proved by quotes and the technical report; the second by the loss of value the defect caused at the date of sale, with comparables; the third by the duration and the use lost. Here the refund retained, 15,000 €, corresponds to what an informed buyer would have knocked off the price for a damp basement room; the works, 72,000 €, correspond to what it costs to make it sound. The court of remittal will have to decide whether the sellers owe the second figure, which requires that they knew of the defect, something a conversion they carried out themselves makes plausible.
Why the gap is so wide. A room fitted out in a basement adds to the sale price far less than its floor area suggests: it does not count as habitable floor area in the regulatory sense if it lacks height or openings, it sells as an improved annex, and the market values it with a limited premium. Curing it durably, on the other hand, means treating the damp from outside, drainage, ventilation, stripping and redoing the fit-out, which often costs more than the premium. The valuation report explains that gap so that the judge is not surprised to see a modest loss of value alongside a high cost.
Fit-out or structure. Insulating, partitioning, tiling and cladding a ceiling is not building a structure: no ten-year warranty, so no building insurance to call on, and the action stays on the ground of hidden defects, with its own rules, the two-year limit, the exclusion clause, the seller’s knowledge. For the valuer, the classification of the works is part of the description of the property: it steers the legal basis and, with it, the measure of the remedy.
Present the claims in order, and quantify them all. The ruling is procedural, but the lesson applies to the report: each claim, main or alternative, must have its justified figure, because the judge must examine them in order and may retain one or the other. A report that quantifies only the loss of value leaves the works claim unproved; a report that quantifies only the works does not say what the price reduction is worth.
The date of sale remains the reference for the loss of value. The partial refund is computed at the day of sale, 2014 in this case, with the prices of the time; the cost of works is updated to the date when they will be done. The report states its valuation dates, without which the two figures cannot be compared.
What the valuer takes from it
- Cost of works, partial refund of the price and loss of enjoyment are three distinct heads, each with its proof and its valuation date.
- A room fitted out in a basement adds little to the price but costs a lot to make sound; the report explains the gap.
- Insulating, partitioning and tiling is not a structure: no ten-year warranty, the action stays on hidden defects.
- The judge examines the main claim before the alternative; the report quantifies both.
- The cost of works is owed only if the seller knew of the defect; the loss of value is owed in every case.
Further reading
The Property loss of value page describes the assignment, its timescale and its fee. The guide I paid too much, can I challenge the price and the glossary entries vice caché, moins-value and surface habitable complement this article. On the same theme: Hidden defect known to the seller: market value caps nothing and Damp wall: does the price reflect the defect?. The decision is available on Légifrance.
What next
A converted room that takes in damp, a high cost of works and a modest loss of value?
I quantify separately the cost of reinstatement, the loss of value of the property at the date of sale and the loss of enjoyment, so that each claim is supported by a figure whatever basis is retained.
Free quote, by email or by phone. No commitment before the quote is accepted. Fees are never linked to the value of the property (Charte de l’expertise, Title I, §2.1).
