📏 Real estate surface areas: understanding the differences for better selling or buying

When you visit or sell a property, a number of figures are displayed: surface habitable, surface loi Carrez, surface utile, surface de plancher... These concepts may seem vague, but they each have their own meaning. very specific role. Let's take a closer look to avoid any confusion when planning your property.

🛋️ Living space: your daily life in square metres

✅ Technical definition (article R111-2 of the Code de la construction et de l'habitation) :

The living area is defined by thearticle R.111-2 of the French Construction and Housing Code.
It corresponds to the built floor areaafter deduction :

• surfaces occupied by walls, partitions, steps and stairwells, service ducts, door and window openings,
• and floor areas for which the ceiling height is less than 1.80 m.

In short, it measures the space that can actually be used for livingexcluding annexes (cellar, garage, balcony, terrace, unconverted attic space, etc.).
➡️ It is used, for example, to calculate the surface area of social housing, to calculate certain taxes, or to check compliance with regulatory minimum standards for habitability.

The living area is the sum of the floor areas rooms for residential useafter deduction :

• of surface area occupied by walls, partitions, steps and stairwells,
• from ducts, door and window frames,
• surfaces whose ceiling height is less than 1.80 m.

❌ Not included:

• Cellars, basements, garages
• Balconies, terraces, verandas
• Unconverted attic

Usefulness: this surface is mandatory in all lease contract empty or furnished (excluding second homes).

🏙️ Carrez Law surface area: for co-owned properties

✅ Definition (Act no. 96-1107 of 18 December 1996) :

The private surface area of a co-ownership lot, known as the Carrez lawThis includes all the floor areas of enclosed and covered premises, after deduction :

• from walls, partitions, markets, stairs, ducts
• from door and window frames
• areas with a ceiling height < 1.80 m

❌ Excludes :

• parts under 8 m² (unless adjoining a main room),
• cellars, garages, car parks, unfinished attics, balconies and terraces

Usefulness: must be mentioned in the the deed of sale of a co-owned property. In the event of an error > 5 %, the purchaser may request a price reduction.

🛠️ Useful surface area: a broader view of potential

✅ Definition (referenced in HLM standards and town planning):

Useful area = living area + 50 % of ancillary surfaces (loggias, balconies, cellars, converted attics accessible from the inside).

📌 This area is not regulated but is often used:

• in new developments (particularly low-cost housing),
• for estimates of value or renovation plans.

Tip: it gives a more complete picture of the usable space of a property.

📄 Floor area: for building permits

✅ Definition (article R111-22 of the Town Planning Code):

The floor area corresponds to the sum of enclosed and covered areascalculated on the basis of inner surface of facades, outside :

• exterior walls,
• Unconvertible attic space,
• car parks, undevelopable cellars, plant rooms, etc.

🎯 It is used for :

• determine whether a planning permission is required,
• calculate land use coefficient (COS),
• assess the development tax.

Important information: not to be confused with the living area. It is often higher.

🤔 Why are these differences crucial?

• 📉 A overestimated surface can lead to legal dispute.
• 🏢 In co-ownership, an error in the Carrez surface area can invalidate a sale.
• 🧾 When renting, failure to state the floor area can invalidate the lease. lease agreement.
• 🏗️ In construction, an error in floor area can block planning permission.

✅ Quick summary of surface areas

Now that you've mastered these different surfaces, you have all the keys you need to move forward with confidence ! Whether you're buying, selling or renting, this knowledge will enable you to talk to professionals on an equal footing and make the best decisions.

💡 Remember the essentials Each surface has its own purpose, and knowing them gives you transparency and peace of mind. No need to worry about unpleasant surprises!

🏡 Your property project is a great adventure. With these clear guidelines, you can now live it to the full, with complete peace of mind. We wish you a safe journey to your future home!