As part of the “Grande Brera” project, a reinforcement intervention was carried out involving the floors of “Palazzo Citterio”, a historic building located in the centre of Milan, to house the new gallery dedicated to 20th century paintings by Lombard artists. Diagnostics and preliminary safety checks highlighted the need to perform a consolidation intervention to increase the shear resistance of the floors. In particular, FRCM-SRG composite systems with steel fabrics combined with rolled steel profiles were adopted; solutions that also offer a better fire resistance than FRP systems. The article illustrates the project, technologies, materials, executive details and acceptance tests. Each floor is characterized by a grid slab with a span of 11.25 m and a width of 20 m. Italian technical qualification and design guidelines were followed. The on-site test used to check the adhesion between the FRCM layer and the properly pre-treated support is also illustrated, the results of which confirmed the predictions made during the calculation.