How serious are vertical cracks in brick walls?

The seriousness of vertical cracks in brick walls depends upon the size and the suddenness of the crack's appearance. Cracks wider than one-fourth inch or that appear suddenly in a few short weeks can be signs of a rapidly shifting foundation that need the attention of a structural engineer.

Most small, slow-forming, vertical cracks are a normal part of the settling process and are only cosmetic in nature. They happen as a result of soil settling beneath the house. All homes settle, but they generally do it slowly over the course of many years and by small degrees. This creates cracks that can either run through the brick or through its mortar.