Common problems: Bulges come from excessive pressure on the back side of a wall. Concrete cracks happen because of horizontal or vertical stress to a masonry surface. (This is why rebar is used to strengthen concrete.)

Discoloration is caused by water penetration or is an indication that water is entering but evaporating.

Deteriorating mortar joints are generally due to age or water penetration.

Leaning walls are usually due to the lack of sufficient footing (additional concrete added to the bottom of a wall to strengthen it) or to more horizontal pressure at the top of the wall than the bottom.

Brick, stone or blocks come apart from age and deterioration of mortar in between masonry units.

Sinking or settling in masonry is due to improper compaction of soil beneath the masonry or improper drainage around masonry.

-- Tips courtesy of HomeAdvisor.com