It introduces the seismic-risk classification of the individual building, in eight classes from A+ to G, and makes it the basis of the Sismabonus. Unlike the seismic zone, which concerns the territory, the class measures the risk of that specific building, with two parameters (PAM and IS-V) and two calculation methods.
It applies to the seismic-risk classification of existing buildings and, in particular, to access to the Sismabonus. The Guidelines are the official calculation tool — in the version substituted by Ministerial Decree no. 24 of 9 January 2020, not the original 2017 one — and are read together with NTC 2018 and Circular 7/2019 for the assessment of existing buildings.
Seismic classification (OPCM 3274/2003) tells how hazardous the territory is; D.M. 58/2017 introduces something different: the seismic-risk class of the individual building. Risk depends on the site's hazard but also on the building's vulnerability and its exposure. A well-built building in Zone 1 may have a better class than a fragile one in Zone 3.
The Guidelines classify risk into eight classes, from A+ (lowest risk) to G (highest). It is a scale as readable as the energy one, but referring to seismic safety.
The class arises from two parameters. The PAM (expected average annual loss) measures the expected cost of damage, year by year: the economic side. The IS-V (structural safety index) measures how close the building is to the required safety level: the life-safety side. The final class takes the worse of the two assessments.
There are two ways to assign the class. The conventional method, based on PAM and IS-V, applies to all building types and can certify even large improvements. The simplified method, reserved for masonry, rests on a quicker typological assessment, but can only attest the current class or a limited improvement. Choosing the wrong method may under- or over-state the result.
Classification is not an end in itself: it is the basis of the Sismabonus, the tax deduction for seismic-risk-reduction works. The pivot remains the designer's sworn statement, certifying the class before and after: an untruthful statement causes loss of the benefit and entails liability. The rate, however, no longer depends on the class jump: up to expenditure in 2024 the benefit grew with the classes gained (70% for one, 80% for two, raised to 75% and 85% on condominium common parts), but the 2025 Budget Law aligned the Sismabonus with the general rates for building bonuses, now graded by the year of expenditure and by whether the property is the taxpayer's main home.
D.M. 58/2017 completes the seismic picture: OPCM 3274/2003 classifies the territory, NTC 2018 set how to design and verify, Circular 7/2019 explains how to apply them to existing buildings, and the Guidelines translate it all into an understandable risk class and an incentive. It is the level at which seismic safety becomes a readable value — for the owner, the market and prevention policy.
Making the existing stock safe is Italy's great seismic challenge. D.M. 58/2017 gives it a grammar and an incentive: it turns a technical concept — vulnerability — into a class anyone can understand and into a convenience that pushes people to act. For an architecture of the existing, it is the tool that ties safety, value and responsibility.
The zone (OPCM 3274) concerns the territory's hazard; the class (D.M. 58/2017) concerns the risk of the individual building, which also depends on its vulnerability. A building in Zone 1 may be in a better class than a fragile one in Zone 3.
Eight, from A+ (lowest risk) to G (highest), on a scale as readable as the energy one.
The PAM is the expected average annual loss from damage; the IS-V is the structural safety index. The class takes the worse of the two, because safety and economy do not offset each other.
The conventional one (PAM + IS-V) applies to all types and certifies even large improvements; the simplified one is for masonry, quicker but limited in certifying class jumps.
It is the tax deduction for seismic-risk-reduction works and rests on the designer's sworn statement, certifying the class before and after the works. Mind the rate: up to expenditure in 2024 it grew with the class jump (70% for one class, 80% for two, raised to 75% and 85% on condominium common parts); from expenditure in 2025 the Budget Law aligned the Sismabonus with the general rates for building bonuses, which depend on the year of expenditure and on whether the property is the main home.
The risk classification before and after the works, sworn by a qualified professional, and compliance with the procedures; an untruthful sworn statement causes loss of the benefit.