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 meters. If the error exceeds 5%, the buyer can demand a proportional reduction in price.
Introduction
In Paris, the price per square meter determines a property’s value. In 2026, with an average price ranging between 9,200 and 10,800 euros/sqm depending on the arrondissement, every square meter counts. A 3 sqm error on an apartment in the 6th arrondissement at 15,000 euros/sqm represents 45,000 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 the loi Carrez measures
- What is included and excluded from the calculation
- The 5% tolerance rule
- Cellars, attics and Parisian special cases
- Recourse in case of measurement error
- The property hunter and surface area verification
What the loi Carrez measures
The loi Carrez surface area corresponds to the floor area of enclosed and covered premises, after deduction of surfaces occupied by walls, partitions, steps and staircases, utility ducts, door and window recesses, and areas where the ceiling height is below 1.80 m.
This measurement applies exclusively to co-ownership units. It does not apply to individual houses sold outside co-ownership, although the habitable surface area (loi Boutin) applies in that case for rental purposes.
The measurement must appear in the preliminary contract and in the notarized 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 excluded from the calculation
The loi Carrez surface 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.
The 5% tolerance rule
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 notarized deed.
In Paris, where prices per square meter 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.
Cellars, attics and Parisian special cases
Parisian buildings 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.
Recourse in case of measurement error
The action for price reduction due to measurement error is governed by article 46 of the law of July 10, 1965. The buyer has one year from the signing of the notarized deed to take action.
The procedure begins with a new measurement carried out by a certified surveyor. If the confirmed discrepancy exceeds 5%, the buyer can formally demand a remedy from the seller by registered letter with acknowledgment 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.
The cost of a loi Carrez measurement by a certified surveyor in Paris ranges between 80 and 200 euros in 2026, depending on the property’s size. This investment 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.
The property hunter and surface area verification
At Home Select, verifying the Carrez surface is part of our standard protocol. Our property hunters systematically check the consistency between the surface stated in the listing, the one mentioned in the survey and the one observed during the viewing.
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.
Over the 1,200 mandates completed 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 formalized, this verification is all the more essential. The property hunter secures the acquisition by ensuring that the true price per square meter 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 notarized 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.
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.
Frequently asked questions
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 notarized 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.
