The design of masonry systems should prevent the intrusion of the elements, rain, snow, heat, and cold, into the building’s interior, and it should safeguard the building’s structural components. Any structural break in the wall could compromise your building envelope. Porous or poor quality masonry units are among the most common failure points, such as:
mortar joints
hairline or shrinkage cracks
parapet
door and window details
Hope that helps?