Loi Carrez: definition and private surface area

The loi Carrez requires the mention of the private surface area in every deed of sale of a co-ownership unit. This surface, calculated according to precise criteria, excludes walls, partitions and spaces where the ceiling height is below 1.80 metres. If the error exceeds 5%, the buyer can demand a proportional reduction in price.

Introduction

In Paris, the price per square metre determines a property’s value. In 2026, with a median price of 9,900 euros/sqm running from 8,200 euros/sqm in the 19th to 14,500 euros/sqm in the 6th, every square metre counts. A 3 sqm error on an apartment in the 6th arrondissement at 14,500 euros/sqm represents 43,500 euros.

Law no. 96-1107 of December 18, 1996, known as the loi Carrez, was adopted to protect buyers of co-ownership units by requiring an objective measurement of surface area. Despite its 30 years of existence, this law remains a source of confusion for many buyers, and of litigation. Our property hunters systematically verify the consistency of stated surface areas during every viewing.

Table of contents

• What exactly does the loi Carrez measure?
• What is included and what is excluded?
• What happens if the gap exceeds 5%?
• How are attics, mezzanines and cellars counted?
• What recourse do you have for a measurement error?
• How does a property hunter check surface areas?

What exactly does the loi Carrez measure?

The loi Carrez surface area is the floor area of enclosed and covered premises, after deduction of walls, partitions, steps and staircases, utility ducts, door and window recesses, and any area where the ceiling height is below 1.80 m. It applies exclusively to co-ownership units.

Individual houses sold outside co-ownership fall outside it: there, the habitable surface area (loi Boutin) applies, for rental purposes.

The measurement must appear in the preliminary contract and in the notarised deed. The absence of a Carrez surface mention in the deed of sale renders the sale voidable, at the buyer’s request, within one month.

It is important to distinguish the Carrez surface from the habitable surface (loi Boutin) and the usable surface. The Carrez surface includes spaces that are not habitable (for example, a built-in cupboard with ceiling height above 1.80 m), while the habitable surface excludes certain spaces such as unconverted attics.

What is included and what is excluded?

Every room of the private unit with a ceiling height of at least 1.80 m is counted, built-in cupboards included. Excluded are areas below 1.80 m, walls and partitions, utility ducts, balconies, terraces and loggias, along with cellars, garages and parking spaces, even when sold as separate private units.

The loi Carrez surface therefore includes all rooms of the private unit (living room, bedrooms, kitchen, bathroom, hallways, dressing room) where ceiling height reaches or exceeds 1.80 m. Built-in cupboards and storage are counted if their ceiling height exceeds 1.80 m and they form part of the private unit.

Excluded from the calculation are surfaces with ceiling height below 1.80 m (under sloping attics, under stairs), walls, partitions, steps and staircases, utility ducts and door and window recesses.

Balconies, terraces and loggias are always excluded from the Carrez surface, as they are open spaces. Enclosed and heated conservatories can however be included if they form part of the private unit.

Garages, parking spaces and cellars are excluded even if they constitute separate private units. This exclusion is a frequent source of confusion in Paris, where cellars are often presented as an asset, rightfully so, without being included in the Carrez calculation.

What happens if the surface gap exceeds 5%?

The buyer obtains a price reduction in proportion to the missing surface, to be claimed within one year of the notarised deed. Below a 5% gap, there is no recourse at all.

The law provides for a 5% tolerance between the stated surface and the actual surface. If the discrepancy is 5% or less, the buyer has no recourse. If the discrepancy exceeds 5%, the buyer can request a proportional reduction in price.

Here is a concrete example. An apartment in the 11th arrondissement is sold for 650,000 euros for a stated surface of 55 sqm Carrez. After verification, the actual surface is 51 sqm. The discrepancy is 4 sqm, or 7.3%, above the tolerance threshold.

The buyer can request a proportional price reduction: 650,000 euros x (4/55) = 47,273 euros. This claim must be filed within one year of signing the notarised deed.

In Paris, where prices per square metre are among the highest in France, this mechanism protects buyers against significant amounts. A 2 sqm discrepancy in the 7th arrondissement at 20,000 euros/sqm represents a 40,000 euro loss.

How are attics, mezzanines and cellars counted in Paris?

Only the part of an attic above 1.80 m in height counts: an attic presented as 25 sqm may be worth just 15 sqm Carrez. A mezzanine only enters the calculation if it is fixed with 1.80 m above and below it, and a cellar is never counted, whatever its size.

Parisian buildings do present configurations that complicate the Carrez calculation.

Converted attics are a frequent source of errors. In Haussmann buildings in the 8th or 9th arrondissement, top-floor apartments often include mansard areas where only part exceeds 1.80 m ceiling height. Only that part is counted in the Carrez surface. An attic presented as “25 sqm” may only count as 15 sqm Carrez if the roof slope reduces the usable height.

Mezzanines are included in the Carrez calculation if they are fixed (non-removable), if their ceiling height exceeds 1.80 m, and if the height beneath the mezzanine also exceeds 1.80 m. A mezzanine that does not meet these conditions is not included in the Carrez surface, even if it is presented as an “extra room.”

Cellars are never counted in the Carrez surface, regardless of their size or how they are fitted out. A 15 sqm cellar unit in the 5th arrondissement does not change the apartment’s Carrez surface, even though it adds asset value to the property.

Conservatories and winter gardens, common in ground-floor apartments with gardens, are included only if they are enclosed, covered and integrated into the private unit.

What recourse do you have for a measurement error?

An action for price reduction, governed by article 46 of the law of July 10, 1965, to be brought within one year of signing the notarised deed. It starts with a new measurement carried out by a certified surveyor, billed at 80 to 200 euros in Paris in 2026.

If the confirmed discrepancy exceeds 5%, the buyer can formally demand a remedy from the seller by registered letter with acknowledgement of receipt, enclosing the new measurement certificate.

In the absence of an amicable agreement, the buyer can refer the matter to the judicial court. Case law is consistent: if the error exceeds 5%, the seller must refund the portion of the price corresponding to the missing surface area.

That measurement cost, which varies with the property’s size, is negligible compared to the amounts at stake.

It should be noted that the seller does not have a reciprocal recourse: if the actual surface is greater than stated, they cannot claim an additional payment. The mechanism exclusively protects the buyer.

How does a property hunter check surface areas?

By cross-checking three sources: the surface stated in the listing, the one on the measurement certificate and the one taken with a laser rangefinder during the viewing. At Home Select, this check is part of the standard protocol of our property hunters in Paris.

This verification relies on several tools. A laser rangefinder allows rapid room-by-room measurement. The apartment floor plan provided by the seller or agency is compared against actual measurements. Previous surveys, where available, are compared with the current measurement certificate.

Across the 1,200+ acquisitions supported since 2011, we have identified significant discrepancies in approximately 8% of cases. These discrepancies most commonly involve attics presented with an overstated Carrez surface, mezzanines incorrectly included in the calculation, and partitions not deducted.

For off-market properties, where information is sometimes less formalised, this verification is all the more essential. The property hunter secures the acquisition by ensuring that the true price per square metre corresponds to the market for the arrondissement.

FAQ

Are cellars and attics included in the loi Carrez surface area?

Cellars are never included in the loi Carrez surface area. Converted attics are included if their ceiling height exceeds 1.80 m and if they constitute a private co-ownership unit. Unconverted attics or those with ceiling height below 1.80 m are excluded from the calculation.

What should you do if the loi Carrez surface is more than 5% less than stated?

If the actual surface is more than 5% less than that stated in the deed of sale, the buyer has one year from the signing of the notarised deed to request a proportional reduction in price. This action is provided for by article 46 of the law of July 10, 1965.

Does the loi Carrez certificate have an expiry date?

The loi Carrez certificate has no legal expiry date. It remains valid as long as no work modifying the private surface area has been carried out. In practice, if the certificate is more than 5 years old or if work has been done, it is recommended to have a new measurement taken.

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Want to be certain of a property’s actual surface area? Our property hunters verify every measurement before making an offer. Contact Home Select for rigorous support throughout your acquisition.