Decoding Concrete Block Wall Cracks
Cracks in concrete blocks in your basement foundation don’t have to be a mystery. The types of concrete block cracks can help you decode your foundation issues.
Concrete or cinder blocks are known as “concrete masonry units” (CMU) in the building industry. In a foundation or basement wall, the blocks are joined together by mortar.
Concrete block wall cracks offer clues to diagnosing a variety of foundation problems. A good starting place is answering several questions about the crack.
1. In What Direction is the Concrete Block Wall Crack Going?
Perhaps no question is more important in discovering the cause of foundation block wall cracking than this. Different types of pressure will generally cause differently shaped cracks. Here are a few examples:
Stair Step Cracks
Stairstep cracks generally run along the mortar joints between the blocks traveling down the wall in a pattern that mimics the look of stairs.
Finding a stair step or diagonal crack zig-zagging up your concrete block wall is usually an indication of soil pressure or settlement. If you see this type of crack in conjunction with other typical signs of foundation problems, there is a good chance that uneven settlement is causing the issue.
The crack also could be caused by soil movement resulting from the ground’s freezing and thawing cycle.
It is a good idea to have this type of crack inspected by a foundation professional. Although the crack doesn't always indicate structural problems, the possibility is likely enough where it is a good idea to have it checked out.
Horizontal Cracks
While hairline horizontal cracks might end up being a minor issue, large horizontal cracks or horizontal cracks that are growing often indicate a serious structural issue that should be addressed.
These cracks are often caused by external pressure, likely hydrostatic (water) pressure from the surrounding soil, pressing the walls inward. A horizontal crack can also appear as a result of a one-time event, such as backfill damage.
If the cracks are caused by an ongoign issue, they are the first step. If the issue is left unchecked, the wall will likely bow and possibly shear or fail. The earlier the problem is caught, the less intrusive the repairs likely will be, so don't put off contacting a professional until it looks like the wall is in danger of imminent collapse.
Vertical Cracks
Vertical cracks aren’t as common as diagonal or horizontal cracks and are generally looked at as less serious than horizontal or stairstep cracks, especially depending on the answers to the next two questions..
Among the possible causes are temperature-fluctuation shrinkage or carbonation shrinkage. An external force, such as an impact on the wall, could also result in vertical cracks.
2. How Large is the Foundation Wall Crack?
Identifying the type of crack your block wall foundation has is the first step. The next is looking at the length and width of the crack itself.
Hairline cracks, especially short or vertical ones, are often not a structural issue. These cracks are generally less than a tenth of a millimeter wide.
The longer or, especially, wider the crack is, the more likely it is that it is signaling a serious problem.
3. Is the Block Wall Crack Growing?
Even if the crack isn't terribly wide yet, if it is growing, that is a worrying sign. That means that whatever force caused the crack is likely an ongoing issue.
Periodically monitor any cracks in your block walls to see if the crack is widening or lengthening. If it is, the time is likely right to schedule an inspection with a foundation repair professional.
Find a Foundation Repair Contractor
If you have a concrete block wall crack that you even suspect might be structural in nature, the next step is to contact an experienced foundation repair specialist to diagnose the cause of the crack. My Foundation Repairs has a nationwide network of foundation repair contractors who are highly trained and use only high quality foundation repair materials. Let us help you find a contractor in your area.
