What should you check before buying a flat in Barcelona?

Aluminosis: why Barcelona buyers ask about it

Aluminosis is the deterioration of concrete made with high-alumina (aluminous) cement, used in Spain mainly in precast floor joists. Barcelona City Council's history of Turó de la Peira, in the Nou Barris district, records that a building there collapsed in 1990 because aluminous cement had been used in much of the neighbourhood. Its tall blocks had gone up between the 1950s and the 1970s, and the later renewal demolished whole blocks, strengthened many flats and built new ones.

According to the Barcelona association of building surveyors (CAATEEB), the Catalan construction technology institute then surveyed about a thousand buildings in 300 Catalan municipalities and concluded that the whole post-war housing stock needed attention. In 2003 the Catalan government also listed La Trinitat, in Barcelona, among neighbourhoods being rebuilt because of structural defects such as aluminosis.

That history does not mean every flat from the period is affected. The same CAATEEB article notes that Catalonia had more than a hundred joist makers, who used both aluminous and ordinary Portland cement, and that joists from the 1950s and 1960s no longer lose strength on their own: what damages them is damp, which rusts the steel inside.

A city of 1960s flats

The 2021 census counts 76,057 homes in buildings from 1951-1960 and 204,691 from 1961-1970: together 280,748, a little over a third of the 794,568 Barcelona homes with a known date. That is the window the CAATEEB links to aluminous cement, 1950 to 1970. Another 218,770 homes are in buildings older than 1951, where the questions shift to façades, roofs, wiring and timber or iron floors.

On a viewing, look at the ceilings of bathrooms, kitchens and the enclosed balconies called galerías, and ask the community of owners (comunidad de propietarios, the body that runs the building) whether floors have been repaired. The minutes of its recent meetings show approved works and one-off levies (derramas).

The inspection certificate the seller must hand over

In Catalonia every residential building must pass a building inspection (ITE) before it turns 45, counted from the year recorded in the Catastro, Spain's property register of buildings. The Catalan Housing Agency applies this under Housing Act 18/2007 and Decree 67/2015. Given Barcelona's housing stock, almost any building on the market should already have one.

The inspector grades defects as minor, significant, serious or very serious, and the certificate of fitness (certificat d'aptitud) lasts 10 years with no or minor defects, 6 years with significant ones and 3 years with serious or very serious ones once safety measures are in place. Without those measures the certificate is refused.

For a buyer, the key rule is that the seller must hand over this certificate when a home changes hands. Ask for it before signing the arras, the deposit contract that usually precedes completion in Spain, together with the full inspection report listing defects and deadlines. The Agency stresses that the inspection is visual and never aims to find hidden defects.

Flood zones between two rivers and the sea

Overlaying the municipal boundary on the official flood maps of the Spanish environment ministry (SNCZI) gives 4 areas of potentially significant flood risk (ARPSI, the EU Floods Directive designation) and river flood zones that reach the city already at the 10-year return period. That is a city-wide figure, not a verdict on your street.

What matters is the plot. A high floor on a sloping street and a ground-floor flat by an old watercourse are very different cases. If you are buying at street level, a converted shop or a building with an underground car park, ask the community whether water has ever come in.

Radon and earthquakes: what the rules say

Spain's building code places Barcelona in radon zone I (appendix B of document DB-HS6). In that zone new buildings and some renovations need a barrier between the ground and living spaces. The zone is a classification of the municipality and does not measure radon in any home; in a 1960s block, the useful question is whether the flat is in contact with the ground and well ventilated.

Spain's seismic code, NCSE-02, gives the city a basic ground acceleration of 0.04 g, the same as its neighbours in the metropolitan area.

What the HOUSINGFAX report covers in Barcelona, and its limits

The report runs 22 checks on any Barcelona address. Check 03 uses the Catastro year to give an aluminosis risk level in words; check 10 overlays the plot on the 10, 100 and 500-year flood maps; check 22 reads the radon zone; check 07 compares the asking price with the housing ministry's average appraised value, which stood at €4,681.5/m² in the first quarter of 2026, 12% up on a year earlier.

There are two Catalan sources we do not check yet. We do not check the Catalan register of building inspections, so the building condition (check 01) only appears if you upload the inspection report as a PDF. Nor do we check the energy certificate register of the Catalan Energy Institute (ICAEN) yet, so check 06 shows no data and you should ask the seller for the label. The report does not replace a technical inspection of the building.

Start with the free report, which shows the checks with the building's real data. The essential report costs €11 and the complete report, which adds the recorded building condition, €19, delivered as a PDF in minutes with a one-off payment.