Habitable floor area (surface habitable)

The surface habitable (habitable floor area) is the regulatory reference area for a dwelling in France. The French Construction and Housing Code defines it as the built floor area, after deduction of the areas occupied by walls, partitions, steps and stairwells, ducts, and door and window openings. No account is taken of unconverted lofts, cellars, basements, sheds, garages, terraces, loggias, balconies, outdoor drying areas, conservatories, glazed volumes, common rooms and other outbuildings, nor of parts of premises with a ceiling height below 1.80 metres.

It is the area that must appear in a residential tenancy agreement (Law of 6 July 1989), and it is the one that experts, notaires (French civil-law notaries) and transaction databases use to express a price per m² for a house or a flat. It is generally slightly lower than the Carrez floor area of the same dwelling, since the latter counts conservatories and certain enclosed and covered outbuildings.

Where the rule comes from

Article R. 156-1 of the French Construction and Housing Code, as specified by the decree of 30 June 2021, gives the definition, which the Charte de l’expertise en évaluation immobilière (the French property valuation charter) restates in Title III, § 3.3.1. Article 3 of the Law of 6 July 1989 requires it to be stated in the tenancy agreement, and article 3-1 allows the tenant to obtain a proportionate rent reduction where the actual area is more than one twentieth below the area stated.

In a valuation report

I measure or check the habitable floor area during the visit, from the plans where they exist and with a laser measure, and state in the report the area adopted and its source (my own measurement, certificate, plans). I use it as the unit of comparison for dwellings, making sure that the comparables are expressed in the same area: a reference expressed in Carrez area or in “usable” area including a conservatory or a converted garage distorts the comparison. Ancillary areas (garage, outbuildings, convertible loft, terrace) are valued separately, as a sum or by a stated coefficient.

Example

Single-storey house with an extension: main rooms 96 m², heated conservatory 14 m², garage 22 m², unconverted loft. Habitable floor area: 96 m² (the conservatory is excluded by the text). The price per m² in the area, taken from sales expressed in habitable floor area, is €2,400, that is €230,400. I add the conservatory at 40 % of the unit value (€13,400) and the garage at €12,000, giving a value of €256,000 rounded. Had the report applied €2,400 to the 110 m² “lived in” by the owner, it would have overvalued the property by €8,000 without saying so.

Not to be confused with

The Carrez floor area concerns only co-ownership lots and follows its own exclusions. The surface de plancher and the taxable area are planning and construction tax concepts. Usable area, in commercial property, follows other conventions.