The F1, F2, F3 nomenclature is based on the count of main rooms in a dwelling, excluding the kitchen, bathroom, and toilets. An F1 has one main room, an F2 has two (typically a living room and a bedroom), and an F3 has three. The letters F (function) and T (type) are interchangeable: an F2 and a T2 strictly refer to the same dwelling.
Carrez law surface area and decent housing standards: what really changes the classification
The classification by number of rooms says nothing about the surface area. Two apartments labeled F2 can have considerable differences in living space. We regularly observe F2s where the bedroom is close to the regulatory threshold, which poses a concrete problem at the time of resale or rental.
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The decree of January 30, 2002 (amended in 2023) sets the decent housing criteria for a room: minimum surface area, ceiling height, and opening to the outside. A room that does not meet these criteria cannot be counted as a main room. A plan sold as F2 with a windowless or too narrow bedroom will, in law, be reclassified as F1 or T1 bis.
Several judgments rendered by the judicial courts of Paris and Lyon between 2022 and 2024 have reclassified F2s as studios or T1 bis due to non-compliant bedrooms, sometimes leading to a reduction in sale price or rent. Before buying, we recommend checking the Carrez law surface area of each room, not just the total area listed in the advertisement.
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Since 2023-2024, the portals SeLoger, Leboncoin, and Bien’ici encourage professionals to specify the Carrez law surface area and the living space, which is starting to limit classification abuses. But control remains partial, and the vigilance of the buyer remains the best guarantee.
To properly understand the difference between an F1, F2, and F3 apartment, one must go beyond simple room counting and examine the compliance of each space with decent housing criteria.
Classification discrepancies between regions and real estate professionals
The F1/F2/F3 typology is not standardized at the national level. Some agencies and developers apply the Boutin law reference (living space), while others reason solely in terms of the number of main rooms. The same plan can be presented as F2 by one player and F3 by another, depending on how a large living area is interpreted.
The so-called “bis” rule illustrates this ambiguity well. A room exceeding thirty square meters is sometimes counted as two rooms, transforming an F2 into an F2 bis, or even into an F3 in some listings. No legislative text sets a precise threshold for this division, leaving room for interpretation by ad writers.
Consequences on the price per square meter
In tight markets (Paris, Lyon, major metropolitan areas), a change in category by just one room significantly alters the displayed price. An apartment presented as F3 appears more competitive per square meter than an F2 of equivalent size, simply because the announced number of rooms inflates the perception of space.
We recommend systematically comparing the price per square meter based on the Carrez law surface area, not on the displayed F category. A measurement diagnosis performed by a certified professional eliminates any ambiguity.
Common pitfalls when purchasing an F1, F2, or F3
Three situations frequently arise in acquisition files, and each can alter the actual value of the property:
- The open kitchen to the living room, sometimes counted as an additional room by the seller even though it does not constitute a main room in the regulatory sense. An F2 with an open kitchen remains an F2, not an F3.
- The mezzanine without sufficient ceiling height, presented as a bedroom. If the height does not meet the decent housing threshold, this space does not count towards the main room total.
- The dressing room or alcove office, labeled as an “extra room” in the listing. Without a window or compliant surface, this space is not a room in the legal sense.
Checks before signing the preliminary agreement
The Carrez law diagnosis is mandatory for any condominium lot. We recommend cross-referencing it with the surveyor’s plan and verifying that each declared room meets three cumulative conditions:
- A sufficient floor area to be classified as a main room
- A ceiling height compliant with the decent housing decree
- An opening to the outside (window or French door) ensuring natural light
If any of these conditions are lacking for a room, the actual classification of the property is one level lower than that displayed in the advertisement.
Rental investment: which typology to favor according to the market
The choice between F1, F2, and F3 depends on the targeted rental market. In the city center of major metropolitan areas, the F2 offers the best compromise between rental yield and reduced vacancy. The rental demand for F2s comes from both young professionals and couples, which broadens the pool of potential tenants.
The F1 often generates a higher gross yield, but the rental turnover is faster and vacancy periods are more frequent. The F3 attracts more stable profiles (families, shared housing), with a higher overall rent but generally lower yield per square meter.
In the suburbs, the logic reverses: F3s find tenants more easily, as families seek space at moderate prices. The local market dictates the typology, not the other way around.
Before any acquisition, checking the actual classification of the property by cross-referencing the Carrez diagnosis, the plan, and the decent housing criteria remains the most protective reflex. A compliant F2 is always worth more than a fanciful F3 in the listing.