How to tell if a house in Italy is at risk of landslides

Two checks on the address are needed, and they should be read together. The first is the map of landslide hazard zones in the plans of Italy's river basin authorities, which ISPRA (the Italian Institute for Environmental Protection and Research) combines for the whole country; the second is the inventory of landslides that have already happened, which tells you whether the ground around has moved before. On top of these comes a figure measured by satellite: whether the ground under the building is sinking.

Landslide hazard levels

In the hydrogeological plans (PAI) the zones where a landslide can happen are divided into four levels, plus attention areas, where a hazard is possible but has not yet been classified. The report uses plain words and keeps the code in brackets:

If the zone does not touch the parcel but is less than 100 metres away, the section is worth considering, whatever the level. A landslide does not stop at the property line: an embankment above the house or an unstable stretch of the access road matter as much as the ground under the foundations.

The national map the report uses is ISPRA's 2024 combined map (mosaicatura). It counts 1,060,084 areas, of which 148,294 have very high hazard (P4) and 267,808 high hazard (P3). Each river basin authority drew its areas with its own criteria: ISPRA has made them as consistent as it can, but some differences between districts remain.

Landslides that have already happened: the IFFI inventory

The inventory of landslides in Italy (IFFI), compiled by ISPRA with the Regions and the autonomous Provinces, records the landslides surveyed across the country with their outline: more than 600,000 of them. The plan says where a landslide could happen, the inventory where one already has.

The report counts the recorded landslides that touch the parcel, those less than 100 metres away and those less than 500 metres away, with the type of movement: fall, slide, slow or rapid flow, sinkhole. A landslide that touches the parcel or lies within 100 metres makes the section worth considering even where the plan marks no zone; those between 100 and 500 metres help you understand the slope and do not change the assessment. If the inventory is not available for the area, the section says so.

The inventory has two limits worth knowing. It does not say whether a landslide is still active or has been made safe, and the absence of recorded landslides does not rule out a hazard.

Ground that is sinking

The third figure comes from the European Copernicus service (EGMS), which uses the Sentinel-1 satellites to measure how many millimetres a year the ground sinks or rises, on a grid of points 100 metres apart. The report takes the points near the building and works out the middle value: within 2 millimetres a year, up or down, the ground is stable; between 2 and 5 downwards it is sinking slowly; from 5 upwards it is sinking markedly. When the speed changes by 4 millimetres a year or more between nearby points, the report flags it, because uneven sinking puts more strain on a structure than even sinking.

In the centre of Forlì, in Corso della Repubblica, the report finds 24 measuring points within 250 metres and ground sinking slowly, by about 3.4 millimetres a year. This is common on the plains and often causes no problems, but if the building has cracks it is worth having a surveyor look at it. The phenomenon is called subsidence: it is a different phenomenon from a landslide, and it leaves similar marks on houses.

What to ask before buying

Cracks are the first sign. Ask the seller whether the building or the parcel has ever had cracks, settlement or ground movement, and whether any strengthening work has been done; it helps to have the paperwork for the works and the name of whoever designed them.

If the house stands on a slope, ask whether there is a geological report, prepared for the construction or for later works, and what it says about the ground. A surveyor or engineer you trust can look at the retaining structures: retaining walls, embankments, drainage, the road up to the house.

The Comune (the local council) is the place to ask whether the recorded landslides near the property are still active or have been made safe, and whether the landslide and flood plan limits renovations, extensions or new building on the parcel. In very high or high hazard zones this is the most important question, together with the one about the hydrogeological restriction (vincolo idrogeologico, R.D. 3267/1923) if the house is in the hills or mountains.

What the report tells you

Type in the address: straight away and free of charge you see the liveability index of the area, which also takes landslides, flooding and earthquakes into account. In the full report the landslide section says whether the cadastral parcel falls in a zone of the plan, how much of it is affected, what level lies within the surrounding 100 metres and how many recorded landslides there are nearby, with a map one kilometre across showing the zones by level and the outlines of the landslides. Where there is no cadastral parcel, as in the province of Bolzano, the check uses the address point and a 100 metre circle, and the report says so. Ground movement has a section of its own. Questions about cracks, retaining walls and limits on works appear in the buying guide when the section finds hazard zones or recorded landslides nearby.

A green result means checked. In the Rimini example the section is favourable because there are no hazard zones in the parcel or the 100 metres around it and no recorded landslide within 500 metres, while the same building is critical for flooding (How to tell if a house in Italy is in a flood zone).

For land, the report is created from the sheet and parcel numbers or from coordinates, and the free land summary already gives area, slope and altitude: Check land in Italy before you buy it.

Limits and sources

The national combined map has no legal value: for an official check the binding document is the plan of the river basin district authority, adopted in the planning documents of the Comune. The report does not replace a site visit by a geologist or surveyor, and landslides are not included in the calculation of what floods and earthquakes cost on average, because no open model exists to work it out.

The sources are ISPRA, Mosaicatura nazionale delle aree a pericolosità da frana PAI (v. 5.0 - 2024), licensed under CC BY 4.0, and the Inventario dei Fenomeni Franosi in Italia (IFFI) by ISPRA with the Regions and autonomous Provinces, licensed under CC BY-SA 4.0: what the report derives from the inventory, including the Rimini figure quoted here, is distributed under the same licence. Both can be viewed on IdroGEO. For ground movement, the Copernicus European Ground Motion Service. How we use them: Landslides and flooding.

Frequently asked questions

Does a recorded landslide nearby mean the house is in danger?

Not on its own. The inventory records landslides that have happened, without saying whether they are still active. It is a good reason to ask the Comune whether the landslide has been made safe and to have a surveyor look at the slope and the retaining walls.

Does the report replace a geological survey?

No. The report tells you what the public maps show for the parcel and its surroundings. The condition of the ground under the building can only be established on site by a geologist or surveyor.

Can a house in a very high hazard zone be renovated?

It depends on the rules of the river basin authority's plan for that zone, which can limit extensions and new building. The report prepares the question for the Comune; the answer comes from its technical office.

Does the check work for land too?

Yes. Choose "A plot of land" and find the parcel with the sheet and parcel numbers or with coordinates: the report checks landslides, flooding and ground movement just as it does for a house.