Until 1 March 2012, the habitable surface area of properties was based on the gross floor area (SHOB) and the net floor area (SHON). Since Ordinance no. 2011-1539 of 16 November 2011, published in the Official Journal on 17 November 2011, came into force on 1 March 2012, SHON and SHOB have been replaced by " floor area ".
According to the new article L. 112-1 of the French Town Planning Code, the floor area covers "the sum of enclosed and covered floor areas, under a ceiling height of more than 1.80 m, calculated from the inner surface of the building's facades".
In addition, article R. 112-2 of the French Town Planning Code states that the following must be deducted from the floor area:
1° Areas corresponding to the thickness of walls surrounding door and window openings to the outside;
2° Voids and hollow spaces relating to staircases and lifts;
3° Floor areas with a ceiling height of 1.80 metres or less;
4° Floor areas laid out for the parking of motorised or non-motorised vehicles, including access ramps and manoeuvring areas;
5° Floor areas of attics that cannot be converted for residential use or for professional, craft, industrial or commercial activities;
6° The floor area of technical premises required for the operation of a group of buildings or a building other than a detached house within the meaning of article L. 231-1 of the French Construction and Housing Code, including waste storage premises;
7° The floor areas of cellars or storerooms attached to dwellings, where these premises are served only by a common area;
8° A surface area equal to 10% of the floor areas allocated to dwellings as they result, where applicable, from the application of the previous paragraphs, where the dwellings are served by internal common areas.
The main advantage of this new calculation method is that it does not include external walls, to avoid penalising owners who use thick walls or double walls to insulate their buildings, in terms of building rights.
This reform therefore makes it possible to increase overall buildability in relation to the SHON, while encouraging improvements in the energy performance of buildings.
From now on, a 1000m² plot with a COS of 0.20 will allow 200m² of floor area to be built, rather than 200m² of net floor area.
