If you learn to read brick properly, you can easily determine whether damage to a brick wall is merely a surface disturbance or, a sign of a serious foundation crack. "Reading brick" means understanding what causes a specific type of damage on a brick and mortar structure. There are limited number of reasons brick or mortar cracks or shifts and they are easy to learn. Recognizing the type of damage you see can help you identify and properly address foundation cracks before they bring down a brick wall.
Look for any loose bricks or missing mortar. This is evidence of damage that has occurred above a structure's foundation. The cause may be rotted wood inserts, water, or improper sand blasting. This type of damage does not indicate foundation issues and is considered a surface or cosmetic repair.
Check for a section of bricks with their top layer peeling off or coated with a rust-like powder. This is called "spalling" and is caused by water absorption and repeated freezing and thawing - usually at grade level. There may also be missing or worn mortar between the bricks, Again, this is surface damage and does not indicate a foundation crack.
Step back and look at the wall. If you see a crack in the mortar that runs from the ground up but displaces no brick or mortar (the mortar is cracked but not falling out) you know that the crack is being caused by a downward pressure, from the house settling over the foundation. A foundation is cracked through upward pressure.
Look at the brick along any crack that is running through the mortar. If any of the brick is cracked or pushed in or out of the level of the wall and the cracks are running in a stair-stepped fashion then you have a foundation crack that must be addressed.
Hold a level to the wall. Your brick wall should be flush to the level while the level is in balance. If your wall is bulging (inward or outward) this is a very serious indication of foundation cracks and the wall is in danger of collapsing. It must be repaired immediately.