How do cracks in walls develop?
Cracks in walls are the result of movement beyond that which can be accommodated by the masonry construction materials. A wall tends to crack where masonry is over-stressed and least restrained, such as at window and door openings or at corners. Stress and movement is usually caused by variations in moisture content in the walls, or in the ground that supports them, temperature variations or chemical reactions. Some movements are cyclic and reversible, many are permanent.
Cracks in walls can be divided into three categories:
- active - cracks in masonry that are increasing in width and/or length
- passive - cracks in walls that are not increasing in width or length and
- cyclic - cracks in brickwork that open and close seasonally.