Saleable area in Monaco: the IMSEE method and usable living space
Distinguish between indoor and outdoor spaces to compare floor areas. AI-generated conceptual illustration; fictional property.
In Monaco, the square metres advertised for an apartment do not necessarily correspond to the space you will have inside. The saleable area, a reference in the Monegasque market described by the IMSEE, includes the footprint of the walls and certain outdoor spaces. It is therefore essential to understand what the figure displayed covers before comparing two properties or calculating a price per square metre.
For a buyer, two pieces of information are complementary: the surface area used for the commercial comparison and the interior surface area that is actually usable. By interior surface, we refer here to the space measured inside the dwelling, excluding the walls and partitions. A recent dimensioned plan makes it possible to compare these two surfaces and explain their differences.
How to calculate the saleable area according to the method described by IMSEE?
In its methodological note, IMSEE describes the following conventions:
| Element Measured | Treatment indicated by IMSEE |
|---|---|
| Facade boundary | Measurement up to the outside of the wall: its thickness is included |
| Wall separating the apartment from the common areas | Measures to the middle of the wall thickness |
| Balconies and loggias | 100% retained surface area |
| Roof terraces and gardens | Surface area retained at 50% |
The technical expressions used are “nu-extérieur” (outer face) and “entraxe” (centre line). They describe the limits of the measurement: we do not stop at the interior facing of the walls. Source: IMSEE, Real Estate Observatory 2025, page 22.
Fictitious example: a built-up area of 100 m², measured according to these limits, supplemented by 20 m² of balcony and 20 m² of roof terrace, gives:
100 + 20 + (20 × 50%) = 130 m² of saleable area.
These 130 m² do not therefore refer to 130 m² of interior living space. Also ask how each exterior was classified. The word "terrace" in an advertisement is not enough to determine whether it is a loggia, a balcony or a roof terrace: the coefficient of 50% should not be applied indiscriminately to all exteriors.
Which area do agencies use to calculate the price per square metre?
The saleable area is a common reference for real estate listings and comparisons in Monaco. However, a section entitled "total area" or "living area" does not guarantee, on its own, that the measurement follows this convention exactly. Ask the agency for the details of the calculation and the document from which the surface area comes.
In our example, a hypothetical price of €6.5 million divided by 130 m² gives €50,000/m² saleable. Dividing it only by the available interior space would produce another ratio. Comparing these two results without specifying their basis would be misleading.
To compare several listings, also check whether their price includes a parking space, a storage unit or other ancillary areas. Present these elements separately and compare prices covering the same components. The price asked by a seller should also not be confused with the price actually obtained during a transaction.
Be careful with statistics: the price of an advertisement divided by its surface area is a calculation specific to this property. The IMSEE indicator is based on transactions and a statistical model: the two figures are not directly comparable. IMSEE methodology.
Consult the prices and statistics of real estate in Monaco as benchmarks, then look for references adapted to the apartment studied.
In old buildings, thick walls can reduce the space that is actually habitable
In many old buildings, the façade walls and some load-bearing walls occupy a large footprint. For a comparable built-up area, the thicker the walls, the less usable interior space remains. Part of the square metres counted in the saleable area corresponds to masonry.
Here is a simplified geometric illustration, without a balcony or interior partition:
| Same 10 m × 10 m outer shell | 20 cm walls | 50 cm walls |
|---|---|---|
| Surface measured outside | 100 m² | 100 m² |
| Interior dimensions | 9.60 m × 9.60 m | 9 m × 9 m |
| Interior floor space | 92.16 m² | 81 m² |
The difference is 11.16 m², while the external envelope is identical. This example is only used to understand the effect of the walls: it is neither an actual apartment measurement nor a coefficient applicable to Monegasque buildings.
A building’s age is a factor to check, not a fixed rule. The structure, insulation, ducts and successive transformations also influence the available space. A recent building can also have thick walls. The apartment should be measured, rather than arbitrarily deducing a percentage of its advertised surface area.
Are the surface areas included in the deeds of sale in Monaco?
The surface area is not systematically mentioned in the deed of sale. Check with your notary the surface areas indicated in your documents and the scope of the clauses: the area stated in the listing is not automatically guaranteed by the deed.
The method described by IMSEE is a market convention, not a law requiring a certified measurement for each sale. The Civil Code nevertheless provides for the possible consequences of a deviation when the sale includes an indication of surface area, according to the conditions and clauses of the contract. Civil Code, Articles 1458 to 1464.
Inaccurate information may also engage the agency's liability. On 28 January 2020, the Monaco Court of Appeal held that there had been a breach of the duty to inform concerning an incorrect surface area, despite the absence of a surface area in the deed. Decision of the Court of Appeal.
Before the acquisition, have the apartment measured
We recommend that you involve a surveyor or an architect who is competent in measurement, who is used to Monegasque practices, before committing to the purchase. This check is particularly useful if the plan is old, if the surfaces diverge or if renovation work has changed the layout.
Ask for a dated survey report that includes:
- a dimensioned plan corresponding to the apartment visited;
- the detail of the interior space, room by room, excluding the walls and partitions, with the measurement convention explained;
- the external surfaces measured separately, their nature and the coefficients used;
- the reconstruction of the saleable area and its comparison with the advertisement;
- the identification of annexes, inaccessible areas and possible calculation assumptions.
The physical survey and the legal verification complement each other. The professional measures; the notary examines in particular the extent of the property being sold and the rights attached to a terrace or garden. A measurement does not, on its own, create a right of ownership over a space.
If a discrepancy appears, have it clarified before signing a binding offer. This is part of the checks before buying an apartment in Monaco.
Compare apartments on a clear basis
The right reflex is to ask for the detailed saleable area, the usable interior space and a recent plan. This will allow you to compare prices while appreciating the square metres that are really adapted to your lifestyle.
Are you considering a purchase in Monaco? Contact Monaco Properties on the areas advertised and the documents to be checked.
Sources verified on September 15, 2026. Fictitious numerical examples, with no appraisal value of a particular property.
