The same house can carry three different floor areas across three documents, and all three are correct. It is neither an error nor a trick, but a consequence of area being measured in more than one way. The problem only appears when you compare two listings that use different methods, because then you are comparing a price per square metre against something that is not the same measure.
This guide explains which figures exist, where they come from, and how to get from them to a comparison that means something.
Why one house has three different areas
In the documentation for a single family house you will typically meet the following:
- Gross building area (GBP) from the building permit. Measured to the outer edges of the structure, storey by storey, and used to check the build against the spatial plan. It is an administrative figure, not a sales one.
- Actual, or gross, area from the design. The sum of every space in the room schedule, including terraces, balconies and loggias at full value.
- Usable, or weighted, area from the same design. The same list of rooms, each multiplied by a coefficient reflecting how genuinely usable that space is as living space.
On a house with a lot of outdoor space, the gap between the second and third figures can be fifty square metres or more. Apartments add a fourth figure, the net usable area from the condominium study, which usually counts enclosed space only.
What the coefficients do
Usable area exists because a terrace is not a living room. Project documentation therefore weights spaces, most commonly like this:
- Enclosed living space: coefficient 1.00
- Loggia: around 0.75
- Covered terrace: around 0.50
- Balcony and covered passage: around 0.25
The exact coefficients are not universal and can differ between projects, so always check them in the room schedule itself. What does not change is the principle: the more open a space is, the less it contributes to usable area.
Why this changes the price per square metre
Take a house with 180 m² of enclosed space, a 40 m² covered terrace, a 20 m² balcony and a 10 m² loggia.
- Sum of all spaces, that is gross: 250 m²
- Usable area: 180 + 20 + 5 + 7.5 = 212.5 m²
The difference is 37.5 m², or fifteen percent. At a price of one million euro that is 4,000 euro per square metre on the gross basis, or 4,706 euro on the usable one. Same house, same price, an impression that differs by almost eighteen percent.
Now imagine comparing that house against another advertised on usable area. Without checking the basis you would conclude the first is cheaper per square metre, and it is not. That is the most common and most expensive mistake made when comparing offers.
What we publish
We put usable area in the area field and state the gross figure in the property description. We do it because usable is the only number that allows an honest comparison of price per square metre, and because publishing the gross figure would make our listings look better value than they are. You can check that on every listing in our current properties.
Other figures in a design worth understanding
Storey notation, for example S+P+1
The notation lists the levels: S is basement, P is ground floor, and the number gives the upper floors. S+P+1 means three levels. It is useful because it tells you immediately how much of the house is dug into the slope, and a basement is almost always darker and cooler than a ground floor.
Building coefficient
The ratio of the building footprint to the plot area. If the plan allows at most 30 percent, then on a 500 m² plot the footprint cannot exceed 150 m². This is why small plots are built upwards rather than outwards.
Utilisation coefficient
The ratio of total gross building area across all storeys to the plot area. A coefficient of 0.55 on a 500 m² plot means at most 275 m² in total. From that figure you can work out in advance how much may be built on a plot at all.
Level 0.00 and height above sea level
A design will state something like "0.00 = 101.13", meaning the ground floor sits 101 metres above sea level. It is one of the most useful numbers in the whole file, because it tells you at once whether you are looking at a house by the sea or a house with a sea view. The difference between level 22 and level 101 is the difference between the beach underfoot and a drive to it.
Building height
Measured from the finished ground level to the top of the cornice or parapet, with the plan setting a maximum according to the number of storeys. If the designed height sits close to that maximum, raising the roof or adding a floor later is not an option.
Old stone houses: often there is no design at all
Everything described so far assumes a design exists. With the old stone houses that Pelješac has in quantity, it often does not. The area then comes from a surveyor’s report or from a legalisation decision, and is as a rule measured to the outer face of the walls.
With stone construction that is a large difference. Walls are often sixty to eighty centimetres thick, so a house measuring a hundred square metres externally can hold around seventy inside. If you are thinking about a renovation, work with the internal measurement, not the one in the decision. The simplest check is to measure the rooms on site and compare against the total in the listing.
On a house for renovation it is also worth asking whether an occupancy permit or at least a legalisation decision exists at all, because without one there is neither a reliable area nor a clear starting point for the rebuild. We cover that in more depth in the guide to buying off-plan.
Land: the plot area is not the area you may build
Land carries its own set of figures. The plot area in the cadastre and in the land registry sometimes differ, because the cadastre is a surveyed record of shape while the land registry is the legal record of ownership. For a purchase the land registry governs, and any discrepancy should be cleared up before the contract.
More important than the area itself is what may stand on it. The land-use certificate and the spatial plan give you the building and utilisation coefficients, from which the maximum footprint and total floor area follow. An 800 square metre plot with a building coefficient of 0.30 and a utilisation coefficient of 0.60 allows a 240 square metre footprint and 480 square metres in total. More on this in the guide to building versus agricultural land.
What to ask the seller for
- The room schedule from the main design, with the coefficients and both totals
- Which figure was entered in the listing, and on which basis
- The building permit, which states the GBP and the plot area
- For apartments: the condominium study, with the list of appurtenant parts
If a seller cannot say which basis was used for the area in the listing, that is an answer in itself.
The most common mistakes
- Comparing price per square metre between two properties without checking whether the areas were calculated the same way.
- Assuming the figure in a listing is enclosed living space. It often is not.
- Forgetting that pools, garages and plant rooms frequently carry their own figures outside the headline area.
- Looking only at square metres and not at level and orientation, which on the coast drive value just as hard.
Next step
If you are looking at a new build, read the guide to buying off-plan as well, because with projects under construction all of these numbers appear before anything exists. For the costs on top of the price there is a separate guide to purchase costs. If you have a specific listing and are not sure what its figure means, send it to us and we will tell you.
Villages covered in this guide
About the author
Sottomonte
Real estate agent
Lives and works on Pelješac. Handles sales, from stone houses for renovation to building land by the sea. Checks the land register, cadastre and permits personally before any offer goes out.