The research work aims at investigating the effectiveness of a minimally invasive strengthening technique used to repair a full scale two-storey building, consisting of 350 mm thick double-wythe rubblestone masonry walls a timber floor and a timber roof with clay tiles. The strengthening technique consists in applying on the external façade of the building a single layer of Composite Reinforced Mortar (CRM) system, which consists in a coating containing a Glass Fiber Reinforced Polymer (GFRP) mesh. The retrofitting intervention included the adoption of artificial diatones connecting both wythes of the walls as well as the installation of steel tie rods at first floor level and steel X-bracings at roof level. The reverse cyclic load was applied to each of the two longitudinal walls of the building by means of a servo-controlled hydraulic jack provided with a vertical load distributor beam. The latter allowed to split the total lateral force into two forces, acting at first floor and roof level, which were distributed proportionally to the first vibration mode of the building.

The first cyclic test was performed on the Unreinforced Masonry (URM) building in order to attain a damage pattern complying with the ultimate limit state condition of the structure.  After pre-damaging, the building was repaired (RM) with the proposed technique and tested again up to failure. The experiments proved the effectiveness of the proposed strengthening method in improving the resistance (240%), the displacement capacity (150%) and the total dissipated energy.  The importance of the artificial diatones to prevent the in-plane detachment of the strengthened wall leaf from the unstrengthened one was also highlighted.