Floor area (Carrez Law)

Carrez Law measurement: certifying the private floor area

The Carrez Law measurement consists of precisely establishing the private floor area of a co-ownership lot. This measurement, governed by law since 1996, expresses the floor area of enclosed and covered premises, after deducting walls, partitions, steps, stairwells, ducts and door and window recesses. It is a key legal figure recorded in every deed of sale of a co-owned dwelling.

The specific feature of this measurement is that it counts only areas where the ceiling height reaches at least one metre eighty. Lower areas, frequent under attics or sloping roofs, are therefore excluded from the calculation.

Why this measurement binds the seller

The declared area is not merely a sales argument: it legally binds the seller. A buyer pays partly according to the square metres declared, and the law grants them protection in the event of an unfavourable discrepancy. This is why the reliability of the measurement is decisive for the security of the transaction.

Which properties are concerned and when

The measurement is mandatory when selling any lot or fraction of a co-ownership lot with an area of at least eight square metres. This covers flats, but also certain commercial or professional premises subject to the co-ownership regime. By contrast, detached houses not subject to co-ownership fall outside the scope of this obligation.

This area must not be confused with the habitable surface known as the Boutin Law area, required for residential leases: the two notions rely on different calculation methods and do not serve the same purpose.

What the professional measures on site

• The floor area of each room, measured at ground level between the interior walls.
• The ceiling height, in order to exclude areas below one metre eighty.
• The deductions for walls, partitions, steps and stairwells.
• The treatment of cupboards, mezzanines and atypical spaces according to their configuration.
• The distinction between the areas taken into account and excluded annexes such as cellars, garages or balconies.

How the intervention unfolds

The diagnostician visits the dwelling equipped with measuring instruments, most often a laser rangefinder, to survey each room. The duration depends on the surface and the complexity of the layout, but generally remains contained. Access to all rooms is essential, including storage spaces and areas under the roof. Having the lot’s floor plans available makes the work easier and improves the reliability of the result.

What the certificate contains

The document provided states the total private floor area expressed in square metres, usually detailed room by room, along with the precise identification of the lot concerned. This certificate is appended to the preliminary agreement and then to the final deed of sale.

A validity linked to the state of the property

The measurement is not subject to a calendar deadline: it remains valid as long as no works alter the surface of the lot. Merging rooms, creating a mezzanine or any transformation changing the volumes makes a new measurement necessary. In the absence of any change, the certificate retains its value over time.

The risks of a floor area error

The law strictly frames the consequences of a discrepancy. If the actual surface turns out to be more than five per cent smaller than the one stated in the deed, the buyer may bring an action for a price reduction proportional to the shortfall, within one year of signing. This action represents a significant financial stake for the seller, which justifies entrusting the measurement to a rigorous professional.

The price of the measurement and its variables

The cost depends above all on the surface to survey and the complexity of the layout: a studio is measured faster than a large duplex apartment. The location and the bundling of the measurement with other diagnostics within the same sale file also influence the final rate, which is often more advantageous when several services are ordered together.

Frequently asked questions about the Carrez Law

Do a balcony or a terrace count in the Carrez area?

No. Balconies, terraces, loggias, cellars, garages and parking spaces are excluded from the calculation, as they do not meet the definition of an enclosed and covered private area set by the law.

Is the Carrez area the same as the habitable surface?

No. The habitable surface, known as the Boutin Law area, follows distinct calculation rules and is used for renting. The two values may differ for the same dwelling, so they should not be confused.

Can the seller measure their own apartment?

Nothing formally forbids it, but it is strongly discouraged. A method error exposes the seller to an action for a price reduction. Calling on a professional guarantees a compliant measurement and legally secures the sale.