What a bowing wall looks like
A bowing wall does not happen overnight. It moves a little each year, so it is easy to miss until it is plain to see. Here is what most people notice first:
A long sideways crack
It runs across a block wall, often about halfway up or a few rows below the top. This is the most common sign.
A bulge you can see
Stand at one end of the wall and look along it. A belly in the middle means it has moved.
Blocks that stick out
One row of blocks sits further into the room than the rows above and below.
A gap at the top
The wall pulls away from the wood beam that sits on it, called the sill plate.
Stair-step cracks at the corners
The ends of the wall crack as the middle pushes in.
Water at the crack
The sideways crack seeps or leaves a white crust after rain.
A quick home test helps. Hold a long, straight board or a level against the wall from top to bottom. If there is a gap in the middle, the wall is bowing.