Property floor areas: how to compare square metres
A property can have an interior usable area, areas measured including walls, ancillary spaces and land. Documents may apply different criteria depending on their purpose. Before comparing numbers, identify the designation of the area, its source and the spaces included.
A house advertised with 150 m² does not necessarily offer more interior space than one advertised with 130 m². The first may add dependencies that the second presents separately. Comparison only becomes useful when the bases are equivalent.
The main designations
| Designation | What to look for | Care when comparing |
|---|---|---|
| Usable area | Usable interior surface under the applicable criterion | Do not confuse it with an area measured to the outside of walls |
| Private gross area | Tax area measured with walls and separating elements | May include spaces you would not assume from the photographs |
| Dependent gross area | Covered, enclosed spaces for exclusive use with an ancillary function | Do not attribute the same use to the dwelling and the dependencies |
| Construction area | Area determined under the planning context and applicable criterion | Ask for the definition and the source of the figure |
| Footprint (implantação) | Surface of the building's footprint on the ground | Does not equal the sum of the floors |
| Plot area | Size of the property or plot | Not the same as buildable area |
Apartment A
Apartment B
Advertising A as “125 m²” would hide a difference that matters to anyone looking for living space.
What the tax register says about private and dependent area
Article 40 of the CIMI (the municipal property tax code) defines private gross area by reference to the outer perimeter and the axes of separating elements. It includes certain private spaces with a use identical to that of the property. Dependent areas are covered, enclosed surfaces for exclusive use with an ancillary function, such as garages or storage rooms, under that article. [1]
This classification must be read in the specific document. One basement may have different characteristics and framing from another. The informal designation used by the owner is not enough to determine the category.
How to compare two homes
Illustrative example: apartment A has 100 m² of private gross area and 25 m² of dependencies. Apartment B has 115 m² of private gross area and no dependencies. Adding A's areas and advertising only “125 m²” would hide a difference that matters to someone looking for living space.
Prepare the comparison with the areas separated. Then consider the layout: a long corridor, the position of doors or the geometry of the rooms can affect how the square metres are used.
Do balconies and terraces count towards the area
Ask for them to be presented separately and for their framing to be clarified. A terrace for exclusive use deserves a precise description of the right of use and the documentation supporting it. Avoid automatically turning an outdoor area into interior area in the listing.
For a buyer, the useful question is: “What space am I acquiring, with what use and based on which document?” For a seller, the answer should be prepared before viewings.
How to calculate the price per square metre
Always state the denominator. In a €500,000 example, dividing by 100 m² gives €5,000/m²; dividing by 125 m² gives €4,000/m². The price is the same and the difference results only from the area used.
A commercial analysis should also consider location, condition, floor and specific features. A price per square metre without a common criterion can lead to a wrong conclusion about the price.
What to do when documents differ
Gather the plans, the tax register and the registry and identify exactly where the difference lies. Ask a qualified technician to clarify measurement criteria and any alterations. Do not choose the largest number merely because it is more favourable to marketing.
Frequently asked questions
Are usable area and habitable area synonyms
They should not be used without identifying the applicable definition. Different concepts may include or exclude circulation spaces, bathrooms and storage. [2]
Is a garage worth the same per square metre
A comparison should separate the function and usefulness of each space. The commercial contribution depends on the property, the location and the alternatives available.
Does a large plot allow a large house
The size of the plot does not, by itself, demonstrate building capacity. That requires its own planning analysis.
Which area should appear in the listing
Present the relevant areas with their designation and source. Where there is doubt, clarify it before communicating a figure as definitive.
Sources
Next step
The Valle team can help you prepare a clear presentation of your home's areas and features before it goes to market.
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