What a bowing wall looks like
A bowing wall is a basement wall that leans or bulges in toward the room. It almost never happens overnight. Most people notice it a piece at a time.
A long sideways crack
It often runs along a mortar joint, about halfway up a block wall.
A bulge in the middle
Hold a long level against the wall. A gap at the middle means the wall has moved.
Stair-step cracks at the ends
Zig-zag cracks near the corners often show up with the sideways crack.
Blocks that stick out
One row of blocks sits past the row below it.
A wall that slides at the bottom
The base of the wall is pushed in past the top.
Water along the crack
The crack opens a path, so damp spots often follow.