Diagnosing Concrete Cracks in Poured Foundations

Diagnosing Concrete Cracks in Poured Foundations



Any crack in your foundation is never a good thing. However, not all foundation cracks are equal. Some are structural caused by settlement issues in the soil while others are simply the culprit to your wet basement.

The sad truth is: Concrete can’t help but crack. It naturally expands and shrinks with the change in the elements. The soil around the wall is going through the same expanding and shrinking process with the weather-shrinking in droughts and expanding in floods. Tree roots, hydrostatic pressure, erosion, and settlement, can all cause cracks in foundation walls.

Foundation repair contractors learn to diagnose concrete foundation cracks to determine what is truly causing the cracks and the severity of the problem.

Let’s start with the basics: Horizontal or vertical?

Horizontal Cracks
Generally horizontal cracks are structural cracks usually caused from pressure building up on the opposite side of the wall from either an composer  improper backfill or hydrostatic pressure. It could also be from cold climates with extreme freeze and thaw cycles.

For these types of structural cracks in poured foundation walls, it is best to use low-pressure crack injection. Epoxy seals the crack and because epoxy doesn’t flex like polyurethane, it is the first step to stopping the crack’s future movement. It is important to know, epoxy by itself will not prevent further cracking. You will need to add more reinforcement such as carbon fiber staples, or other structural products to reinforce the crack.

Simply filling the structural cracks with epoxy will not fix the problem if the wall continues to move. Added reinforcement to the foundation (whether interior or exterior anchors, carbon fiber, or beam systems) will work to stabilize the wall to prevent movement. Such reinforcement in conjunction with crack injection will ensure that the original crack does not reopen while minimizing the potential for further re-cracking in the same area.

Vertical Cracks
Vertical cracks are generally non-structural cracks. They usually are seen with multiple cracks in one or more area along the basement wall. Vertical foundation cracks are often the least threat to the building. They are usually caused by the natural expansion and contraction of concrete. Through the years’ freeze-thaw cycles, the concrete expands and contracts causing the concrete to crack.

When these vertical cracks are straight or slightly wandering and generally even in thickness, the risk is fairly low as far as affecting the structural integrity of the house. Nonstructural cracks can bring on another set of problems with water intrusion, soil gases, insects and other pests. Either polyurethane foams or epoxies are effective in sealing such cracks.

Cracks in Block Walls
Cracks in masonry blocks have to be handled differently from cracks in poured foundations and they trigger different problems and risks. If you have cracks in masonry blocks it usually signifies thermal movement or differential settlement. If there is an even crack through a masonry block wall either in the mortar joints or through the blocks, it is usually caused by shrinkage or thermal exposure. With these types of masonry cracks, the risk of the wall collapsing is low.

The risk increases if you see stepped in brick especially near the ends of the wall. It is especially dangerous if the wall bond courses are broken. If you see a crack that is wider at the bottom than at the top in your block wall there may be a serious risk of collapse.

If the masonry wall is bowing, then you should look into a foundation repair system or a masonry contractor who will rebuild and reinforce the wall.

Get the Whole Picture
While the cracks themselves can tell you a lot about what is truly causing the problem, there may be more to the story. If you have water in the basement, you have to inspect the foundation inside and out to determine the reason for the water. If you don’t go outside you may miss the grade sloping toward the house instead of away from it, or the puddle where the gutter dumps water when it rains.


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