The paper describes the design of the reinforcement of two masonry buildings used by the Ravenna mosaic group, and another known as “stecca”. This building is part of the San Vitale complex in Ravenna. Vulnerability assessments previously performed highlighted several critical issues, both static and seismic. The static issues were related to wooden roofing and steel mezzanines. The seismic issues mainly concerned vertical masonry structures, for which the local overturning mechanisms of the facades and upper faced defined a low seismic capacity building. The main objectives of the design were: 1- improvement of structural safety; 2- reinforce against the seismic action. The focus on conservation aspects has led to the development of a design respecting the historical construction elements. The retrofit, demolition and reconstruction work planned for the mezzanines has also been designed to avoid damaging the building’s historical structure. The interaction with the Italian Conservations bodies, combined with the use of advanced technologies and materials, made it possible to achieve in the intervention project the objectives of static consolidation and seismic reinforcement.