Earthquake risk when buying property in Spain

Spain is not Japan, but neither is it immune to earthquakes. The south and south-east of mainland Spain — and parts of the Pyrenees — face a genuine seismic hazard that building regulations have recognised for decades. If you are planning to buy a home there, it is worth understanding what that means, how it affects the building and how to check it.

Seismic risk is one of the official data points Hogarfax includes in every property analysis, alongside flood risk, radon and planning matters. Here we explain what lies behind that figure and why it matters before you sign.

What is a property's seismic risk?

Seismic risk measures the likelihood of a site experiencing ground shaking of a given intensity over a particular period. In Spain, it is governed by the Norma de Construcción Sismorresistente NCSE-02 (Earthquake-Resistant Construction Standard), which assigns each municipality a basic seismic acceleration (a_b): a reference value, expressed as a fraction of gravitational acceleration (g), used to calculate the resistance a building must provide.

The higher the basic acceleration, the more stringent the construction requirements. The standard sets an important threshold: when a_b is equal to or greater than 0.04g, its earthquake-resistant provisions are mandatory for most buildings. Below that figure, the risk is considered low.

Which parts of Spain have the highest seismic risk?

The hazard is not distributed evenly. It is concentrated in the south and south-east of mainland Spain — Granada, Almería, Murcia, Alicante and Málaga have the highest values — and in parts of the Pyrenees (Huesca and Girona) and southern Catalonia. Much of central and north-western Spain has a low hazard.

How does this affect the home I want to buy?

The most important factor is not only where the home is located, but when and how it was built. A property built in a seismic zone after NCSE-02 came into force (or under its predecessor, NCSE-94) should incorporate earthquake-resistant structural design. Older buildings dating from before any seismic standard are the most vulnerable.

• Age and applicable regulations: check whether the building predates or postdates the seismic standard in force when it was built.
• Structural system: old load-bearing walls, unbraced floor structures or alterations that remove structural elements increase vulnerability.
• State of repair: cracks, settlement or pre-existing defects may worsen during an earthquake.
• Soil type: soft soils amplify shaking compared with rock.

Does it affect the price and insurance?

In Spain, earthquake damage is covered by the Consorcio de Compensación de Seguros (Insurance Compensation Consortium), provided the property has standard home insurance cover. As a result, seismic risk does not usually increase the premium as it does in other countries. It does matter to the purchase decision and negotiations: an old building in a high-hazard area with structural defects presents a risk to your investment that should be assessed — and may justify revisiting the price or commissioning a technical inspection.

How to check seismic risk before buying

There are two levels to consider. The regional level: locate the municipality in the NCSE-02 classification to determine whether it has a low, moderate or high hazard. Then there is the specific property: cross-check that hazard against the home's actual age and characteristics. Hogarfax does both, taking the municipality's official basic acceleration and placing it in context alongside the exact property's other risks and cadastral data.