If you’re planning on starting a renovation that involves an increase in the safety level of your home with respect to seismic activity, it will be useful for you to know the difference between Seismic Adjustment and Seismic Improvement, so that you can choose the most appropriate intervention based on the level of security you intend to reach. In both cases you will be able to access the benefits provided thanks to the legislation on tax incentives, the Sismabonus.

Adjusting or improving a building seismically means rendering it more resistant to an earthquake. While both types of intervention focus on increasing the safety of a building, according to the Technical Regulations for Construction (NTC2018) these two terms have quite distinct meanings.

So let’s take a look together at just what the differences and similarities are between these two types of interventions, so that we can consider with greater awareness which type of intervention to apply to improve the seismic response, and consequently the safety, of your building.

Seismic adaptation and improvement: similarities and differences

Both types of intervention act on existing buildings, with the shared purpose of increasing the degree of safety in response to seismic activity. In particular, in both cases, we cannot ignore the reinforcement and/or modification of the structural elements of the buildings.

The difference is given by the level of seismic safety * achieved after the intervention.

*The seismic safety of a building is expressed through the IS parameter—the seismic safety index (expressed as a percentage), which represents the ratio between the maximum seismic action that can be tolerated by the structure (Peak Ground Acceleration of PGAc for capacity) and the seismic action project maximum for a new construction (Peak Ground Acceleration of PGAd for a new project).

Seismic Adjustment Interventions

Interventions aimed at achieving the level of safety that is required by the legislation for new buildings.

IS-V ≥ 100%

In some cases, the adjustment intervention is not a choice but rather something that becomes mandatory, for example, but not limited to, when any of the following is intended:

  1. the raising of the building;
  2. the increasing of the global foundation loads by more than 10%;
  3. the changing of the intended use of a building (for example from a residential home to a school or other strategic building).

Seismic Improvement Interventions

Interventions aimed at reducing the seismic risk, without however needing to reach the safety minimum required for new buildings. The seismic safety index following the improvement interventions must be increased by a value no less than 10%.

In both cases, therefore, the seismic response of an existing building to the repercussions of an earthquake is improved, by making changes in stiffness, resistance or ductility, due to the reinforcement or the insertion of new structural elements, such as, for example, but not limited to:

  • the. insertion of metal tie rods in the masonry;
  • the laying of classic or fiber-reinforced plasters in the masonry;
  • the injection of thermosetting mortars or resins into masonry;
  • the stiffening of floors with lightweight or fiber-reinforced concrete slabs;
  • the strengthening of reinforced concrete structures with the use of composite materials (FRP).

It is easy to understand that the Seismic Adjustment activities are often much more expensive both from a technical and executive point of view than the Seismic Improvement ones.

Tax concessions for seismic improvement and adaptation activities

Fortunately, certain government-based benefits that provide for a tax deduction for expenses incurred have been introduced, the so-called Sismabonus.

The characteristics of the benefits are laid out in the Order of the President of the Council of Ministers n.3247 of March 20, 2003. This opportunity was introduced by the Ministerial Decree of March 14, 2005, published in the Official Gazette no. 80 of 18 April 2005, and was subsequently extended by Decree 63/2013, converted into Law 90/2013.

Now extended until 2025, the Budget Law 2022, also known as the Sismabonus, incorporates all those interventions providing for the reduction of the seismic risk of an existing building. This risk is classified in Italy on the basis of 4 zones of seismic intensity.

In order to benefit from the Sismabonus, the interventions must be carried out on buildings for residential use, belonging to the cadastral categories A/1, A/8 and A/9, located in the seismic zones 1, 2 and 3.

Reduction of the seismic risk for your building

Before starting any type of structural intervention, the existing construction must undergo a safety assessment that verifies the following:

  • the type of construction of the building (masonry, reinforced concrete, etc.);
  • the geometric characteristics of the elements;
  • the mechanical characteristics of the materials;
  • the geological conditions of the land where the building stands;
  • the presence or absence of land subsidence;
  • the possible presence and extent of existing crack patterns;
  • the resistance of structural and non-structural elements.

This type of assessment will have to determine the safety level of the building pre-intervention and will be aimed at planning the subsequent interventions required to achieve post-projectural levels of security.