Welding specifications

The table below resumes the correspondence between the classes as from the norms. The list is given in terms of importance:

UNI EN 1090-2 / UNI EN 1090-3

EN ISO 5817

Particularity of the executions *


Quality level D

Components with elementary quality requirements of average /low importance


Quality level C

Components with normal quality requirements of average importance


Quality level B

Components with extended quality requirements of average/high importance


Quality level B+

Components with extended quality requirements of high importance. Particulary significant fatigue phenomenons.

 * for more details see the annex B of the EN 1090-2. See the next paragraph for a summary of these details.



As general remark as in this annex B it is reported that the EXC4 should be applied to special structures or structures with extreme consequences of a structural failure as required by national provisions.


For the level B+ the additional requirements to be respected are summarized in the following Table 17.


For what concern the qualification of the welding, as reported in the table A.3, it shall be executed in the frame of the selected execution class and in accordance with the requirements specified in the EN ISO 3834 in the following parts:

  • EXC 1:             EN ISO 3834-4 “Elementary quality requirement”
  • EXC 2:             EN ISO 3834-3 “Standard quality requirement”
  • EXC 3 and 4:  EN ISO 3834-2 “Comprehensive quality requirement”


Drawings prescription


Where a welding is foreseen it is needed to indicate  its execution class and the reference norm.


The general information about the class of welding is one of the following options:


Welding in compliance with the norm EN 1090-2:2011 (for steels) or EN 1090-3:2008 (for aluminum).

a) Execution class EXC1           (equivalent to quality level D as per norm ISO 5817)
b) Execution class EXC2           (equivalent to quality level C with exception as per norm EN ISO 5817)
c) Execution class EXC3           (equivalent to quality level B as per norm EN ISO 5817)
d) Execution class EXC4           (equivalent to quality level B+ as per norm EN ISO 5817)


Each welds must report its execution class that identifies its realization:

-       Execution requirements

-       Needed qualification tests

-       Certification of welders

-       Related documentations


Even if the previous method is more correct it is possible to indicated the welding in compliance with the norm EN ISO 5817 choosing one of the levels below:


Welding in compliance with the norm EN ISO 5817

a) Quality level D
b) Quality level C
c) Quality level B



When not indicated on the drawing it is always intended an execution class EXC2 (EN 1090-2 or EN 1090-3) or a quality level C (EN ISO 5817).