The usable floor area (superficie útil) is the floor you can actually walk on and furnish inside the home; the built area (superficie construida) adds the space taken up by walls, partitions, columns and ducts. The difference between usable and built area is usually between 15% and 25%, and it grows when the figure includes the proportional share of the building’s entrance hall, stairs and corridors.
There is no single national definition valid for every purpose. The most widespread criteria come from the regulations on subsidised housing, the rules of the Catastro (Spanish Land Registry Office) and the ministerial order on mortgage valuations, and each autonomous region and each municipal plan may set its own rules.
Usable and built area of a home: definitions
The most commonly used definition of usable floor area is that of Royal Decree 3148/1978 on officially subsidised housing (Article 4): the floor of the dwelling enclosed by the inner face of its walls, whether these separate it from the outside or from other dwellings and premises.
For the built area, the usual reference is Rule 11 of Royal Decree 1020/1993, which regulates cadastral valuation: the area contained within the outer line of the perimeter walls and, where applicable, the centre line of party walls, once light wells have been deducted.
Order ECO/805/2003 on valuations further distinguishes between built area without common parts and built area with common parts. The second adds to the dwelling the share of the building’s common elements that corresponds to it according to its participation quota.
| Type of area | What it includes | Where it is used |
|---|---|---|
| Usable | Interior floor free of partitions, columns and ducts, plus part of the private outdoor spaces | Subsidised housing, information for new-build buyers, floor-area schedules in the project |
| Built (private) | The usable area plus the dwelling’s partitions, structure, ducts and external walls | Architectural project, construction budgets, valuation |
| Built with common areas | The built area plus the share of entrance hall, stairs, lifts and corridors | Catastro for buildings divided into flats, property listings, valuation |
| Buildable or countable | What the planning regulations count for the purposes of buildability | Permits and development-potential studies for a plot |
What counts and what does not in usable and built area
In the usable floor area under subsidised-housing regulations, the floor taken up by internal partitions, whether fixed or movable, by vertical structural elements and by pipes or ducts with a horizontal cross-section of more than 100 cm² does not count. Nor does floor with a clear height of less than 1.50 m, as happens under a pitched roof.
Private outdoor spaces, such as terraces and drying areas, count at half their area and up to a cap of 10% of the enclosed usable area. Under the cadastral rule, covered balconies, terraces and porches count at 50%, unless they are enclosed on three of their four sides, in which case they count at 100%.
| Element | Usable area (subsidised housing) | Built area (Catastro) |
|---|---|---|
| Façade walls | Do not count | Count up to their outer face |
| Party walls with neighbours | Do not count | Count up to their centre line |
| Partitions and columns | Do not count | Count |
| Ducts over 100 cm² | Do not count | Count |
| Covered terrace or porch | 50%, capped at 10% of the enclosed usable area | 50%, or 100% if enclosed on three sides |
| Areas with a clear height under 1.50 m | Do not count | Do not count in residential use |
| Light wells | Do not count | Are deducted |
These criteria are not universal. Regional habitability standards and municipal by-laws may measure terraces, spaces under the roof or built-in wardrobes differently, so it is worth checking which rule has been applied in each document.
Where each figure appears
The Catastro records built area. For properties under the horizontal property regime (condominiums), the cadastral record breaks down the dwelling and adds the proportional share of common elements, so its total is usually the highest figure of all.
The title deed and the nota simple (Land Registry extract) reproduce the description registered at the Registro de la Propiedad (Land Registry). It may state the usable area, the built area or both, and in older properties it is not always specified which one it is. When it does not match the Catastro, the explanation usually lies in the measurement criterion rather than in an error.
For new-build housing, Royal Decree 515/1989 requires the seller to provide a description of the dwelling stating its usable floor area. Second-hand listings, on the other hand, tend to publish built square metres and frequently include common areas without saying so.
The architectural project includes a schedule with the usable area of each room and the built area per floor. In a mortgage valuation, the area checked by the valuer is used and, if measuring is not possible, the lower of the cadastral and registered figures.
How to compare the price per m² of two homes
Two prices per square metre are only comparable if they have been calculated on the same type of area. A flat advertised in built square metres including common areas looks cheaper per m² than an identical one advertised in usable square metres.
The most reliable method is to bring both homes down to usable area:
- Ask for the dimensioned floor plan or the cadastral record with the breakdown of areas.
- Identify whether the figure in the listing is usable, built or built with common areas.
- Divide the price by the usable area of each home.
- Note terraces, storage rooms and parking spaces separately, as they have a different value per m² from the dwelling.
If only the built area is available, subtracting between 15% and 20% gives an approximation of the usable area, valid only as an order of magnitude. How many usable square metres each household needs is a different question, covered in the guide on how many square metres a house should have.
Example: one flat and its three areas
A flat with 76 m² of free interior floor and a covered terrace of 8 m² has 80 m² of usable area, because the terrace counts at half. Partitions, columns, ducts and external walls take up another 15 m², and the dwelling is allocated a share of 13 m² of entrance hall, stairs and corridors.
| Area | Calculation | Result | Price per m² if it costs €432,000 |
|---|---|---|---|
| Usable | 76 m² + 4 m² of terrace | 80 m² | €5,400 |
| Built | 80 m² + 15 m² of walls and partitions | 95 m² | €4,547 |
| Built with common areas | 95 m² + 13 m² share | 108 m² | €4,000 |
| Difference between the first and the last | 108 m² – 80 m² | 28 m² | €1,400 |
The same flat and the same price give three values per square metre. There is a 19% difference between the usable and the built area, and 35% if the built area with common areas is taken.
Which area is used in construction, refurbishment and buildability
New-build budgets and reference cost modules are expressed per built square metre, because the structure, façade and roof are built over that entire area. The method is explained in detail in the article on how to calculate the construction price per m².
In a full home refurbishment, the items are measured on actual surfaces: floors and ceilings per usable m², tiling and painting per m² of wall. Indicative ratios per square metre may refer to usable or built area, and it is advisable to ask for the quote to state which.
A plot’s buildability is measured in buildable square metres and how it is calculated is set by each municipality’s planning regulations. Planning rules usually exclude certain elements, such as basement garages or uncovered terraces, so the area that consumes buildability does not necessarily match either the actual built area or the cadastral one.
How Cabana handles the floor areas of a project
Cabana is an architecture studio in Madrid that designs detached houses and full refurbishments. On house design commissions, the studio checks the buildability allowed by the planning regulations against the brief and draws up the schedule of usable and built areas for the project, which serves as the basis for the budget and the permit.
In summary
Usable area and built area measure different things: the first, the floor you can actually use; the second, that floor plus walls, partitions, structure and ducts. A third figure, built area with common areas, adds the share of the building and is the one that usually appears in the Catastro and in many listings.
Before comparing prices, signing a purchase or commissioning a quote, it is worth knowing which area is being used and under which rule it was measured. The subsidised-housing and Catastro criteria are the most widespread, but municipal planning and regional regulations may establish their own.
Frequently Asked Questions
Which area should appear in the purchase contract for a new home?
Consumer protection regulations on home sales require the information given to the buyer to describe the dwelling by its usable floor area. The prudent approach is for the contract to also attach the dimensioned floor plan and specify the built area and the share of common areas.
Why does the Catastro show more square metres than the title deed?
The usual reason is that the Catastro adds the dwelling’s share of common elements, while the deed only records the usable area or the private built area. If the difference cannot be explained that way, it may be an undeclared extension or an old measurement, and a correction of the discrepancy can be requested.
Does the terrace count as usable area?
It depends on the rule applied. Under the subsidised-housing criterion, private outdoor spaces count at half and up to a cap of 10% of the enclosed usable area; other regional or municipal regulations apply different rules, especially for uncovered terraces.
Do built-in wardrobes and corridors count as usable area?
Corridors and hallways do form part of the usable area, since they are interior floor of the dwelling with sufficient height. The treatment of built-in wardrobes varies according to regional habitability regulations, so the applicable rule should be checked in each case.
How can the actual area of a home be checked?
The safest route is a survey carried out by a qualified technician, who draws up the plan and calculates the usable and built area under a stated criterion. As a first check, the cadastral record is useful, as it breaks down the dwelling, terraces and common elements.
