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How to calculate the living area of your accommodation?

living space

Until recently, it was difficult to answer this question because there was no clear definition. This vague situation often led to misunderstandings between buyers and sellers, the latter tending to include everything - balcony, cellar, garage - to end up with very large areas and make the sale price more attractive. But things have changed since the publication of the standard on living space in March 2016 by ILNAS 1 .

This national standard 2 , only targets residential property (individual or collective, new or old) and provides a detailed calculation method of accessible living space. It has several advantages. It allows calculation with simple means and within the reach of all purchase prices per square meter. It makes it easier to compare property prices between several houses or apartments in the same district. Finally, it establishes a common language between the various parties concerned:  owners, real estate agents, buyers and notaries.

What are the criteria to apply   ?

According to the ILNAS standard , the habitable surface designates the intramural surfaces (SIM) expressed in square meters. It includes all visible, accessible and measurable interior surfaces, which occupants benefit directly or indirectly. Are therefore included in the calculation living rooms (living room, kitchen, bedrooms, dining room but also dressing room and cupboards), water rooms (sanitary and bathrooms) and circulation areas (corridors, stairs, etc. .). Each area is measured at floor level, just above baseboards. The sum of all the measurements gives the living area of the property.

On the other hand, all rooms not intended for housing are excluded from the living area. These so-called "   accessories   »Include in particular cellars, garages and technical rooms   ; unheated verandas;  terraces, loggias, balconies and dryers outside the accommodation. Usable roof spaces or mezzanines (no floor, bulky frame, difficult access or height less than 2 meters) or usable but not fitted out are also considered as accessory surfaces. In the case of a collective building, the common areas are also excluded.

What about apartment buildings   ?

Everything will depend on the vertical cadastre (the descriptive table of division of the building stopped with the Administration of the cadastre and the topography). If the collective building has one, the calculation of the living area is obtained as follows. We start from the cadastral useful area and deduce from it the areas whose ceiling height is less than 2 meters as well as the areas occupied by partitions.

In the absence of a vertical cadastre , the calculation of the living area is done in the same way as for individual dwellings. We add the living rooms , the water rooms and the outside openings. 

Is a margin of error tolerated? 

Yes. Whatever the measurement, the margin of error tolerated in the calculation of the living area is 5% maximum (above or below the exact area).

Is the ILNAS standard legally binding   ?

No. Even if this standard was published in the Mémorial, it does not have the effect of governing all relations between the parties concerned. The parties to the contract are therefore perfectly free to choose another method of calculation. It is therefore better to specify in the contract whether or not the surfaces indicated refer to the ILNAS standard to avoid any further complications. Indeed, without an exchange of consent on another calculation method in the contract, the courts will apply the standard in the event of a possible dispute.    


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1Luxembourg Institute for Standardization, Accreditation, Safety and Quality of Products and Services

2 called ILNAS 101