This paper presents Croatian standard HRN EN 1090-1:2009+A1:2011 and standard HRN EN 1090-2:2008+A1:2011. Standard deals with the execution of steel and aluminum constructions, and this paper summarizes the norm EN 1090-1: 2009 + A1: 2011 and EN 1090-2: 2008 + A1: 2011, which is primarily related to the execution of steel structures. Since Croatia joined the EU, it is important to be familiar with European standards in general. This European standard is available in tree official editions (English, French, German) and it is prepared by Technical Committee CEN/TC 135. Diploma thesis is designed so that it is composed of two parts. The first part describes in general standard HRN EN 1090-1 that refers to the "Requirements for conformity assessment of structural components" and the "Technical requirements for steel structures". All the requirements and procedures of standards required to be carried out according to the selected class performance are described. Second, practical, part of thesis describes implementation of procedure according to standard on execution of real steel construction which has been made in company “OMEGA”.