How we calculate the ratings

Three colours and a grey

Each section of the report has a rating:

• Favourable (green): no problems emerge at this point for that topic.
• Worth considering (yellow): there is something to look into, for example a hazard area nearby or a medium seismic zone.
• Critical (red): the figure needs attention before you decide, for example a parcel in an area that floods frequently.
• Informational (grey): the section describes without judging, like the cadastral parcel or the population.

We do not give an overall score: risks, services and prices cannot be added together.

Landslides

What counts is the most severe hazard level on the parcel and, with less weight, in the surrounding 100 metres. Very high (P4) and high (P3) hazard areas on the parcel give a critical rating; medium (P2), moderate (P1) and attention areas lead to "worth considering". Landslides recorded in the IFFI inventory that touch the parcel or the surrounding 100 metres also lead to "worth considering".

Flooding

What counts is the most frequent flood scenario affecting the parcel: frequent floods (P3) give a critical rating, less frequent (P2) and rare (P1) floods lead to "worth considering". A scenario that only affects the surrounding 100 metres carries less weight. The meaning of the levels is explained in Flood zones P1, P2 and P3.

Earthquakes

What counts is the higher of the municipality's seismic zone and the expected ground acceleration at the point (PGA), using the same thresholds as the zones: above 0.25 g counts as zone 1, between 0.15 and 0.25 g as zone 2, between 0.05 and 0.15 g as zone 3. Zone 1 is critical, zone 2 worth considering; zones 3 and 4 are favourable, because the hazard is low and covers much of Italy: how the ground shakes right under the house is covered by the microzonation section, where the municipality has the study.

What floods and earthquakes cost

What counts is the average damage a year for a 100 square metre home, adding the middle of the flood range and the average earthquake figure, as a share of the cost to rebuild it: favourable below 1 per thousand (about 150 euros a year), worth considering up to 8 per thousand, critical from there up (over a thousand euros a year). An area that floods about every 30 years is enough on its own for critical; the most exposed seismic areas of Italy stay at worth considering. The section does not go into "What to check first": flooding and earthquakes already have their own sections. The method is in What floods and earthquakes cost.

Services and transport

For services, what counts is the distance to the nearest one in each category: close if it is within 500 metres, less close if it is within 1 kilometre. For transport, what counts is the stops within 500 metres and the type of lines.

Air

What counts is the worst of nitrogen dioxide, PM2.5 and PM10: favourable if all are within the limits that will apply from 2030, worth considering if they are within today's limits but not the 2030 ones, critical if a yearly average exceeds a legal limit in force. If the averages are within the limits but PM10 goes over the daily limit on too many days, the result is worth considering, not critical: this happens across almost all of the Po Valley, applies to the whole city and cannot be changed by choosing a home.

Municipal plan

The rating is informative: the plan says what the parcel is, not whether that is good or bad. It becomes worth considering only for what changes what can be done on the parcel: an area for planned public facilities (the municipality can usually expropriate it) or for public facilities where the mosaic does not say whether they already exist, geological feasibility class 4 of 4, the buffer zones of cemeteries, sewage plants, wells and military easements. Never critical: the planning use certificate is binding. In Lombardy, Veneto, the province of Bolzano and the metropolitan city of Turin; the method is in Municipal plans.

Contaminated sites

The result is never critical: even inside a polluted area we do not know whether the single plot is, the municipality does. It is worth considering if the address is inside a site of national interest or if within 500 metres there is a site with clean-up under way or still under investigation; favourable if there is none within 500 metres. Where the source gives only the municipality and not the position of the sites, the block stays informative.

When a figure is missing

If a source does not cover the address (for example cadastral maps in the province of Bolzano, or timetables in a city without open data) the section says "not available" and explains why. We do not fill the gaps with estimates.

Updates

Each source has its own schedule: cadastral maps every six months, local prices twice a year, street numbers and services every month. The date of each figure is shown under the section. The full list is on Where the data comes from.

Some sources are not redone often. If the most recent data in a section is more than ten years old, we say so in the summary, next to the result, and the section explains why there is nothing newer. This happens with the age and condition of buildings in the area: Istat published them area by area only in the 2011 census. The 2021 census counts the buildings but no longer describes them.

Thresholds may change when the sources change: if that happens, we update this page.