This chapter describes the main causes of damage making use of real cases, referring the reader to literature. It focuses exclusively on masonry construction. Most damage in masonry buildings results from the low tensile strength of the material due to the limited bond between mortar and units. In turn, not all cracked masonry buildings are safe. In addition, other than tension, shear and compression may also induce damage in masonry buildings. According to the stimulating article of J. Heyman, the natural state of the masonry flat arch or lintel is the cracked state. Accordingly, rather than alarming structural problems, cracks often represent a functional expedient of masonry elements to find another resistant scheme. Masonry generally shows a good compression strength that guarantees an adequate behaviour under permanent and service loads in the majority of historical buildings. Problems related to soil settlement can be especially dangerous for load-bearing wall buildings with low-quality masonry or weak interlocking between perpendicular walls.