This is a question we are often asked and the answer is more complex than you may imagine. Cracks in a foundation can range from a normal occurrence to a sign of emanate failure.
First, the basic duties of any residential foundation is two fold one it distributes the perimeter load from the structure to the soil below–it holds the house up. Second, it acts as a retaining wall to resist the lateral soil pressure–it keeps the dirt and water out. Block wall foundations do very well at holding the house up and do well at retaining the soil up to a point. An eight inch concrete masonry unit wall or (CMU as block is called) can only with stand the pressure of about four feet of differential back fill and many basements in our area have eight, nine or even ten feet of back-fill which brings us to the horizontal crack.
The typical block home foundation fails in a bending action, the wall is built and as soil pressure pushes against it. This causes a separation in the mortar joint as the blocks hinge and the hinging or horizontal cracking is usually more pronounced at the middle of the wall and tends to stair step up to the top and or bottom of the wall as it approaches the corners.
The engineering term to classify any horizontal separation at a mortar joint is failure. Now that does not mean the wall is going to fall down tomorrow but it does mean that the failure has begun and left to its own devices it will eventually fall. The prudent action is to arrest the movement so it does not cause problems in other areas of the house. Horizontal cracks in home foundations do not get better they get worse.
The good news is they can be fixed permanently. There are many solutions to address the problem they range from the not so invasive and expensive to the very evasive and very expensive it depends on when you choose to address it. Small hairline cracks are less expensive, large cracks and displacement more expensive. One of our professionals would be happy to come to your house and explain the repair methods and cost to you and would also be even happier to do the repair–contact us today.