Living Space in a Shared Ownership Property: Must a Converted Cellar Be Measured?

You have just purchased a flat in Biscarrosse, with a cellar in the basement. The seller indicated an area of 70 m², but after the sale, you realise that the cellar, although described as such in the deed, has been fitted out as a storage room and measures 10 m². Should it be included in the calculation of the area? This apparently technical question has direct financial consequences: every square metre counts, especially when the price per m² in the Landes region is close to €3,000.

Article 46 of the Law of 10 July 1965 requires that the area of the private part of a co-ownership unit be stated in the sale deed. But what happens if a room, described as a cellar in the co-ownership regulations, is in fact a habitable storage room? The Court of Cassation ruled on 2 October 2013: the trial judges have the power to independently assess the actual nature of the room, regardless of its contractual description. In short, if the cellar has become a storage room, it counts towards the area.

This decision is a breath of fresh air for wronged buyers, but a wake-up call for sellers and their notaries. We will see how this practical case, which could have taken place in Mimizan, ended up before the Supreme Court, and what you should take away from it for your property transactions.

The Facts: An Everyday Story

SCI Sacre (the company) purchased, by notarised deed dated 18 May 2005, a co-ownership unit from the X heirs. The sale deed and the co-ownership regulations stated that the unit included a cellar in the basement. However, after the sale, SCI discovered that this basement room was no longer a cellar: it had been converted into a storage room, with direct access and fittings. The actual area of the private part was therefore different from that declared.

SCI then sued the sellers for a reduction in price on the basis of Article 46 of the Law of 10 July 1965 (which provides for an action for reduction of the price if the area is more than 5% less than that stated). The sellers resisted, arguing that the cellar, even if converted, should be excluded from the calculation of the area because it was described as a cellar in the contractual documents.

The Court of Appeal ruled in favour of SCI, holding that the description as a cellar was not decisive: what matters is the physical reality of the room. The sellers then appealed to the Court of Cassation, but the Court dismissed their argument, upholding the Court of Appeal's decision. In other words, the trial judges independently found that the room was a storage room, not a cellar, and concluded that it should be included in the area. What few people know is that this decision is part of a jurisprudential trend that protects the buyer, prioritising reality over contractual statements.

The Court's Reasoning — Explained

The Court of Cassation relied on Article 46 of the Law of 10 July 1965, which provides: 'Any unilateral promise to sell or buy, any contract that concludes or records the sale of a unit or part of a unit must state the area of the private part of that unit or part of a unit.' In clear terms, the seller must indicate the actual area of the private part, i.e., the rooms used exclusively by the co-owner, excluding common parts.

The sellers argued that the cellar was excluded from the area because the co-ownership regulations and the sale deed described it as a cellar. But the Court of Cassation recalled that the contractual description is not absolute: the trial judges independently assess the nature of the room based on its physical characteristics. In this case, the Court of Appeal had found that the room was no longer a cellar (dark, damp storage space) but a storage room (fitted, accessible). Therefore, it formed part of the private part and had to be measured.

Note, however, that this solution is not a departure from precedent, but a confirmation of earlier case law (Civ. 3e, 9 June 2010, No. 09-13.439). The Court of Cassation leaves a margin of appreciation to the trial judges, which can create uncertainties. But overall, the trend is clear: reality prevails over written statements. undefined that if a 'cellar' is converted into a bedroom, office or storage room, it must be included in the stated area.

What This Means for You — in Practical Terms

For the buyer: You have just bought a flat in Mont-de-Marsan. The deed states 80 m², but after the sale, you discover that the basement, described as a cellar, is actually a fitted room of 15 m². If the actual area is more than 5% less than that stated, you can demand a reduction in price. For example, if the price per m² is €2,500, 15 m² represents €37,500. You can claim this amount from the seller.

For the seller: Be careful not to underestimate the area. If you have converted a cellar into a storage room without mentioning it, you risk an action for reduction in price. Before selling, have the area measured by a professional (diagnostician) and check the exact description of each room. undefined, I have come across cases where the seller had to repay several thousand euros for a simple error in description.

For the co-owner: If you plan to convert a cellar into a living space, be aware that this may alter the co-ownership shares (proportionate share in the common parts) and require the approval of the general meeting. Furthermore, if the conversion is not declared, you may be required to restore the premises to their original state.

Four Tips to Avoid This Type of Dispute

• Have a Carrez measurement carried out by a certified professional before the sale. This document, mandatory for units over 8 m², protects you in case of a dispute. In Biscarrosse, the cost of a measurement is around €150, a trivial sum compared to a potential dispute.
• Check the description of rooms in the co-ownership regulations. If a cellar has been converted, have the regulations amended by the general meeting to avoid any ambiguity. Otherwise, the seller assumes the risk.
• When buying, insist on a warranty clause for the area. Even though the law protects the buyer, a contractual clause can strengthen your rights and facilitate an amicable procedure.
• Keep all documents relating to the condition of the property. Photos, plans, surveys: they will be useful in case of a dispute to prove the actual nature of the room at the time of sale.

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Further Reading: Related Case Law and Developments

This decision is part of a line of cases protecting the buyer. Already in 2010 (Civ. 3e, 9 June 2010, No. 09-13.439), the Court of Cassation had ruled that converted attics must be included in the area, even if described as 'loft' in the regulations. More recently, in 2018 (Civ. 3e, 14 June 2018, No. 17-18.392), it extended this logic to terraces and balconies, provided they are enclosed and covered.

The trend is therefore towards a broad interpretation of the concept of 'private part': any space used exclusively by the co-owner, regardless of its name in the documents, must be measured. However, cellars strictly used for storage without any fittings remain excluded. The boundary can be blurred, hence the importance of an accurate survey.

For the future, we can expect the courts to continue to prioritise physical reality over formal descriptions. Notaries and estate agents must therefore be extra vigilant when drafting deeds.

What You Absolutely Must Remember

FAQ:

Q: Is a converted cellar always excluded from the Carrez area?
R: No, if it is fitted and accessible, it must be included. The description in the deed does not bind the judges.

Q: Can I claim a reduction in price if the stated area is less than the actual area?
R: Yes, if the difference is more than 5% of the stated area. The action is subject to a 5-year limitation period from the sale.

Q: How much does a court action for incorrect area cost?
R: Legal fees and expert costs can reach €3,000 to €5,000, but they are often recoverable if you win. A preliminary 30-minute consultation (€45) may save you from an unnecessary trial.

Q: What should I do if I am a seller and have a converted cellar?
R: Describe it as a 'storage room' in the deed and have it measured. This will avoid any subsequent dispute.

Q: Does this case law apply to leases?
R: Indirectly, because the habitable area (Boutin law) excludes cellars. But if the lease mentions an area including a converted cellar, the tenant may challenge it.

Are you in a similar situation? A first 30-minute consultation with Maître Zakine (€45) can save you months of proceedings — and often much more. Book an appointment →