1.1. Generally, a fissure is a breakage of any material due to tensions on the surface greater than the strength of that material, and usually appears as a shallow longitudinal slit less than a 1mm wide. They are common due to differential expansion and contraction of building materials caused by the annual and daily changes of heat and humidity, especially in façades receiving direct sunlight. Fissures are rarely of structural significance.
1.2. A crack is a breakage that reaches through the entire thickness of the construction element e.g. wall, thus breaking the element into two parts. These could be due to differential movement of the foundations or unplanned overloads, among other reasons. When a crack appears in a structural element, this element loses part or all its strength, making it weaker. Cracks must be checked to decide if they are unimportant, or if they affect the strength of the building and could get worse, in which case the structure may need reinforcement.
