There are several causes and they point to different underlying problems. Hairline cracks in mortar joints are usually the result of normal thermal movement and are generally cosmetic. Stepped cracks following the mortar joints can indicate foundation movement or settlement. Horizontal cracks, particularly in older cavity walls, can indicate failed wall ties. Cracks that are widening over time need investigating before any repair work is carried out. If you have cracks you’re unsure about, we’ll take a look and give you an honest assessment.