What should you check about a Bilbao building before you buy?

A housing stock built mostly between 1951 and 1980

The census counts 165,685 homes in Bilbao. The busiest decade was 1961 to 1970, with 44,185, and more than 100,000 were built between 1951 and 1980, six in every ten. Another 21,249 are in buildings from before 1941.

For a buyer, the age is a checklist rather than a verdict. Blocks from those decades may have original floor joists, roofs and downpipes that have been patched more than once, uninsulated façades and, in the 1970s, materials that can contain asbestos. None of that is assumed for a given building; it tells you what to ask the property manager and what to look at during the viewing.

The Basque building inspection and Decree 117/2018

In Spain, every apartment block is run by a comunidad de propietarios, the owners' association that pays for repairs to shared parts in proportion to each flat's share. In the Basque Country, that association must commission the building inspection (ITE) under Decree 117/2018 of 24 July once a mainly residential building is more than 50 years old, counting from construction or from a full refurbishment, and repeat it ten years after filing the previous one with the city council.

The decree makes the surveyor grade every defect on a five-step scale with a deadline: grade 1 means immediate action within 24 hours, grade 2 very urgent work within three months, grade 3 urgent work within twelve months, grade 4 work after more than a year, and grade 5 routine maintenance with no damage observed. Unrepaired grade 2 or 3 defects usually mean building works soon and a special levy (derrama) that the new owner will share.

Bilbao city council files each inspection in Euskoregite, the Basque Government's register. Under the decree, access to it is public, free and online, so you do not have to rely only on what the seller shows you.

Bizkaia keeps its own cadastre

Unlike most of Spain, Bizkaia keeps its own cadastre (the property survey used for tax), run by the provincial government and published as open data, updated daily. A Bilbao flat does not have the usual 20-character Spanish cadastral reference and will not show up in the national cadastre's website.

HOUSINGFAX finds the entrance in the official Basque street directory and matches its position against the Bizkaia cadastre to read the building footprint, its local reference, the year of construction and the number of floors and homes. Because the Basque sources describe the whole entrance rather than each flat, the report covers the complete building in Bizkaia and does not estimate the price of a specific flat.

The ría, the Nervión and the Cadagua

Spain's national flood mapping system (SNCZI) lists three areas of significant potential flood risk in Bilbao. The largest follows the Bilbao estuary, shared with Erandio, and is classed as both river and sea flooding. The other two follow the Nervión river, through Bilbao, Basauri and Galdakao, and the Cadagua river, through Alonsotegi, Barakaldo and Bilbao.

The ten-year river flood zone crosses the municipality, but that says nothing about a particular address: a block close to the water can sit outside every mapped zone, and one further away inside the 500-year zone. Check 10 of the report overlays the building's plot on those maps and tells you which zone, if any, reaches it. Read it first if you are looking at a ground-floor flat or one with a basement storage room or parking space.

Radon: Bilbao is in zone I

The radon section of the Spanish building code (CTE, DB HS 6) lists Bilbao in zone I of its appendix B. It sets a reference level of 300 Bq/m³ as an annual average in living spaces and requires a protective barrier against radon in new buildings in those municipalities, and in renovation work on existing ones that changes that protection.

The zoning applies to the whole municipality and measures nothing inside a home. The only way to know a flat's radon level is to measure it with detectors for at least three months, worth doing for a ground-floor home or before a renovation. Check 22 of the report places the building on the radon potential map of Spain's Nuclear Safety Council.

Earthquakes and price

Bilbao is not in the annex of Spain's seismic building standard NCSE-02, which only lists municipalities with a basic ground acceleration of 0.04 g or more. For prices, the Ministry of Housing gives an average appraised value of €3,401.8 per m² for private housing in the first quarter of 2026, 10.6 % up on a year earlier. It is a city-wide average, useful to put an asking price in context, not to value a flat.

What the report does not do

HOUSINGFAX gathers what official registers say about the building and its surroundings, each item with its source and date. It does not enter the property and does not replace a technical inspection of the building: if the registered inspection lists structural defects, have a surveyor look at them before you sign the arras, the deposit contract that usually precedes the deed.