Masonry  (brick or stone) walls sometimes show signs of bulging as they age. A wall itself may bulge, or the bulge may only be in the outer leaf. Bulging often takes place so slowly that the masonry does not crack, and therefore it may go unnoticed over a long period of time. The bulging of the whole wall is usually due to thermal or moisture expansion of the walls outer surface, or to contraction of the inner leaf. This expansion is not completely reversible because once the wall and

The effects of the cyclical expansion of the wall are cumulative, and after many years the wall will show a detectable bulge. Inside the building, separation cracks will occur on the inside face of the wall at floors, walls, and ceilings. Bulging of only the outer masonry leaf is usually due to the same gradual process of thermal or moisture expansion: masonry debris accumulates behind the bulge and prevents the course from returning to its original position.

In very old buildings, small wall bulges may result from the decay and collapse of an internal wood lintel or wood-bonding course, which can cause the inner course to settle and the outer course to bulge outward. When wall bulges occur in solid masonry walls, the walls may be insufficiently tied to the structure or their mortar may have lost its bond strength. Large bulges must be tied back to the structure; the star-shaped anchors on the exterior of masonry walls of many older buildings are examples of such ties (check with local building ordinances on their use).

Small bulges in the outer masonry course often can be pinned to the inner course or dismantled and rebuilt.