Technical Standards for Construction (NTC 2018)

In forceStrutturale & SismicaLegge/DecretoCogente● In review

Summary

TAV. 00

The decree governing the design, execution and testing of all constructions in Italy. It sets the safety levels required of structures — new and existing — with a performance-based limit-state approach, and regulates actions, materials, geotechnics and seismic design in a single text.

Scope of application

TAV. 01

It applies to all constructions — buildings, bridges, geotechnical works, structures in concrete, steel, timber, masonry — across the national territory, both for new works and for the assessment of and interventions on existing buildings. It concerns structural designers, works directors, testers, contractors and producers of structural materials.

In depth

TAV. A

How the code is structured

NTC 2018 organises the entire construction cycle into twelve chapters: principles and expected performance, actions (permanent, variable, seismic, accidental), design rules for each structural material — reinforced concrete, steel, timber, masonry, composite structures — geotechnics, testing and existing buildings. The framework is performance-based: the code sets the safety levels and the performance to be guaranteed, leaving the designer responsible for the choices made to achieve them.

Safety verification adopts the semi-probabilistic limit-state method: actions are amplified and resistances reduced by partial factors, and the structure is verified both against collapse (Ultimate Limit States) and in everyday service conditions (Serviceability Limit States: deflections, cracking, vibrations).

Seismic action: from the site, not the zone

The design seismic action is built from the hazard of the individual site (national reference grid) combined with the nominal life of the structure and its use class — from ordinary class II to strategic class IV — and with local conditions: subsoil category and topography. From these follow the response spectra used for design. The dissipative capacity of the structure enters the design through the behaviour factor, linked to the structural type and the chosen ductility class.

Existing buildings: chapter 8

For the existing stock the code introduces the safety assessment — mandatory in defined cases, such as changes of use or significant structural interventions — and three categories of intervention: local repair, affecting single elements; improvement, which raises safety without necessarily reaching new-build levels; and full upgrading, which reaches them. The path runs through knowledge of the building: survey, investigations and knowledge levels that condition the confidence factors allowed in calculations.

Materials and controls: chapter 11

Every material or product for structural use must be identified, qualified — through CE marking where a harmonised standard exists, or through national procedures — and accepted on site by the Works Director, with tests and documentation. It is the bridge between a material's datasheet and its legitimacy for structural use.

The full text of the decree is published in the Official Gazette and can be consulted free of charge at the official source indicated on this sheet.

Key points

TAV. K

Performance-based approach: safety is verified at Ultimate (SLU) and Serviceability (SLE) Limit States with the partial-factor semi-probabilistic method.
Every structure declares its nominal life and use class: from these follows the reference period for the seismic action.
The seismic action is defined site by site (point-based reference hazard), no longer by administrative zones.
Chapter 8 governs existing buildings: safety assessment and three categories of intervention (local repair, improvement, full upgrading).
Chapter 11 requires qualification, identification and on-site acceptance of structural materials and products.
Structural design, works direction and static testing are mandatory, documented acts for structural works.
Circular no. 7/2019 of the Superior Council of Public Works is its application tool: instructions and criteria, with no autonomous innovative value.

Frequently asked questions

TAV. Q

Does NTC 2018 also apply to existing buildings?

Yes: chapter 8 is dedicated to existing buildings. It defines when the safety assessment is mandatory and classifies interventions into local repair, improvement and full upgrading, with increasing requirements.

What are nominal life and use class?

The nominal life is the number of years over which the structure, with ordinary maintenance, must keep its design performance. The use class describes the consequences of interruption or collapse (from ordinary class II to strategic class IV). Together they determine the reference period of the seismic action.

When is static testing mandatory?

For structural works governed by the NTC, static testing is the mandatory final verification, entrusted to a professional independent from design and works direction in the cases provided by law, certifying conformity with the design and the standards.

What is the difference between seismic improvement and full upgrading?

Improvement increases the existing structural safety without the obligation to reach the levels required for new buildings; full upgrading reaches them. The choice depends on the type of intervention: some (e.g. adding storeys) require full upgrading.

Does the NTC replace the Eurocodes?

No: they coexist. The NTC is the binding national code; the Eurocodes are referenced for what is not covered and may be used within the limits set by the NTC itself.

Is a CE-marked material automatically usable structurally?

CE marking qualifies the product, but chapter 11 still requires identification and on-site acceptance by the Works Director, with the controls and documentation required for each material.

Where can the full text be read free of charge?

The decree is published in Ordinary Supplement no. 8 to Official Gazette no. 42 of 20 February 2018, freely available on the Official Gazette website (link on this sheet).

Glossary

TAV. G

Stato Limite Ultimo (SLU): Condition beyond which the structure collapses or loses bearing capacity: SLU verifications safeguard human safety.
Stato Limite di Esercizio (SLE): Condition beyond which the structure no longer meets its intended service requirements (deflections, cracking, vibrations), without collapsing.
Vita nominale (VN): Number of years during which the structure, subject to ordinary maintenance, must remain usable for its design purpose.
Classe d'uso: Classification of the structure by the consequences of loss of operation or collapse, on which the use coefficient for seismic action depends.
Fattore di comportamento (q): Coefficient reducing elastic design seismic forces according to the dissipative capacity and ductility of the structure.
Categoria di sottosuolo: Classification of the foundation soil that modifies the seismic response spectrum according to the properties of the surface layers.
Valutazione della sicurezza: Procedure to establish the safety level of an existing building, mandatory in the cases set out in chapter 8.
Collaudo statico: Mandatory final verification of the structural work's conformity with the design and the standards, certified by a qualified professional.