The scope of our office was the structural assessment of the adequacy of an existing reinforced concrete industrial building with steel roof, due to the increase of the imposed loads in the framework of the extension of the solar panel plant. On-site documentation and mapping of the bearing members of the steel roof was carried out. The surface of the structure is approximately 9.600 sq.m. The outcome of the structural analysis was the need of the strengthening of some of the steel members of the steel roof either with new welded gusset plates or with their lateral restraint or even with their replacement with cross sections of larger dimensions or of better quality etc. The bearing capacity evaluation analysis and strengthening design were carried out with the software Fespa 20 v.8.1.0.22, SAP200 as well as BETON Express from RUNET.