The reason why a crack appears in a wall depends on various factors, such as the wall material, age, environmental conditions and surrounding building structures. These cracks may be cosmetic or they may point to structural damage in your building. Serious cracks may require a call to a structural engineer or remodelling contractor.
Drywall may crack soon after you install it. The joint compound used to hold the drywall pieces together may shrink too much and appear as cracks. The seams between drywall pieces may show through the joint compound and paint. Drywall cracks also often form in areas where humidity fluctuates but temperature remains constant. This is because the drywall expands and contracts with temperature, but only wood changes with temperature. Cracks may also appear if the building foundation or roof moves, pulling the drywall in different directions.
Plaster cracks when it separates from the wood lath behind it, losing its structural integrity. When plaster comes off the lath, cracks will keep reappearing even if you fill the cracks again and again. Plaster also cracks easily from stress if it bends or stretches. Environmental conditions, such as wind, humidity and temperature, may also cause enough stress to crack plaster. Another cause of plaster walls cracking is stress from weight overload.
The Concrete Foundations Association of North America holds the view that cracks are a natural part of concrete walls. Generally, cracks that are smaller than 1/4 inch and don't leak usually don't present serious dangers. One common reason for cracks in concrete is uneven shrinking as the concrete dries, which causes cosmetic cracks in the surface. Other causes of cracks in concrete walls include temperature changes, stress, movements in the building foundation and deterioration of the reinforcing materials.
Around Door and Window Frames
All types of walls commonly develop cracks around the window and door frames. Known as re-entrant cracks, they form when stress accumulates at the corners of the frames. These hairline cracks usually don't cause serious problems. If large cracks appear in these areas and interfere with the opening and closing of the doors and windows, they may indicate a larger problem with the building structure. In such a case, This Old House recommends that you contact a structural engineer or remodelling contractor.