Foundation Crack Illustrations
The following illustration shows a very typical crack that can happen in both poured concrete and block foundations. Both materials shrink as they dry, and tight 90 degree corners are splendid places for cracks to originate.
The key is to monitor the width of the crack. Make a mark somewhere along the crack and measure it accurately with a ruler that has millimeter markings. If the crack starts to get wider at the top or the bottom, it could be trouble.
This crack is one that appears in the horizontal bed joints of either a brick or a concrete block wall. These cracks spell trouble with a capital T. If you see these in your basement block walls, they are a sign that the walls are in the early stages of failure. The pressure of the dirt behind them has bent the wall and the crack is the hinge point. On a brick wall, the cracks can be caused by corroded wall ties or inadequate ties and wind pressure is actually causing the wall to bend.
It is often pointless to repair them as the next time it gets hot, a crack will likely appear in your repair material.
If you see cracks or gaps like this consider them to be huge flashing red lights telling you that major problems are happening somewhere else in the house.