Damages existing in masonry engineeringstructures are caused by various loads and has to be repairbecause of structural and architectural requirements. Repair ofcracked masonries using materials of high stiffness and lowdeformability, like lime and cement mortars or epoxy resins, doesnot increase significantly the tensile strength of the repair joint.This is because of the stress concentration occurrence. The use ofhighly deformable bonding materials allows reducing peaks ofstress concentration, causing (after repair) increase of strength ofcracked masonry elements. Proposed repair materials of highdeformability can be easily covered with original masonrymaterial to ensure protection of architectural value.In the paper, there were tested masonry units (bricks),investigated in two kinds of loading. One of them was the fourpoint bending test on Polish Bonarka bricks and the second onewas the Single Lap Shear Test on Italian Rosso Vivo - A6R55Wbricks, strengthened using CFRP and SRP strips bonded onepoxy resin. In both cases, the primary failure appeared in formof cracks (or detachment) going through the brick materials. Thefailure surfaces of both tests were repaired using materials of lowand high deformability. More significant strength increase of thetested masonry elements (after repair) was obtained in the caseof the use of highly deformable interface materials than of barelydeformable bonding materials.Efficiency of highly deformable repair materials was alsoexamined as repair on cracked masonry walls in laboratory usingpolymer injection and externally bonded composite mats made ofglass fibers bonded on highly deformable polymer. Additionally,the highly deformable polymer joints were tested dynamically insitu on a masonry building, up to failure also
