The aging of a structure often results in small, spiderweb cracks in the ceiling. Seasonal expansion and shrinking can also cause cracks. However, large, parallel cracks in a ceiling often indicate a serious problem.
Given enough time, most homes develop a series of spiderweb cracks that run across the ceilings of all the rooms. Cracks of less than 1/16 inch are not generally an indicator of serious structural damage, but of normal settling of the home. They appear in wallboard and historic plaster. These cracks may affect walls and floor tiles as well. When homeowners find cracks near the walls, they are generally not a reason for concern; however, a large crack that travels across the center of the ceiling is.
Large parallel cracks that extend across the ceiling and down the walls indicate structural damage. The underlying problem could be deterioration of a wall stud or damage due to earthquakes or other types of soil movement. Excessive settling of the foundation sometimes causes this type of damage.
A bow in a cracked ceiling is another indicator of a problem. The bow sometimes indicates damage to a ceiling joist, the structural timber that holds the ceiling in place. When ceilings exhibit bows with cracks, the homeowner should call for professional guidance.