Is Your Foundation Under a Crack Attack?

One of the biggest concerns my clients have may be foundation cracks. If the foundation has problems, the entire structure may be adversely affected. But are all foundation cracks “deal breakers”? Not necessarily. Let’s talk about some of these cracks and their potential cause:



Horizontal cracks in a slab foundation


“Cold joints” (horizontal cracks) are often seen in the exterior of slab foundations of homes built from the 60’s to the 80’s that have a two-pour foundation. A cold joint occurs when fresh concrete is poured on cured or dry concrete. Depending on the width of the crack, it may or may not need repair. Proper drainage around the perimeter of a home becomes very important if a cold joint is present. There is the probability of water migration into the slab which may cause bigger problems.





Horizontal cracks in a raised foundation

Many times, a horizontal crack seen in a raised foundation wall is the result of corrosion of the reinforcing steel (re-bar) within the wall. Excessive moisture may be present or the steel may be located too close to the edge of the wall. This condition should be repaired as soon as possible, or further damage may occur. Many times what may appear as a thin crack at the exterior can be much worse when viewed from inside the crawlspace. Depending on the extent of the corroded steel, this condition may be rather costly to repair.  





Vertical cracks in a slab foundation

Vertical cracking (shear cracks) seen in the perimeter of a slab foundation should always be further evaluated. Excessive moisture, soil movement, settlement, or structural issues may be the cause. To determine the extent of these cracks, the flooring must beremoved/lifted (which is beyond the scope of a home inspection) or a manometer test (slablevelness test) may bedone. Hairline cracks can be found invirtually every slab foundation out there- concrete shrinks and cracks when it dries. Also, a vertical crack is often seen where the garage slab meets the house slab. This is simply a cold joint between the two slabs which are typically poured at different times and should not be a big concern unless excessive width is present.





Vertical cracks in a raised foundation

I will begin here by saying that some thin vertical cracking can usually be found in all raised foundation stem-walls and are not normally a cause for alarm. If the cracks run diagonally, it may be a sign of more serious issues. Heavier cracks should be further evaluated to determine their cause and whether they will negatively affect the structure of the home. Excessive moisture, poor perimeter drainage, soil movement, or improper construction techniques or renovations may be the cause.


4 thoughts on “Is Your Foundation Under a Crack Attack?”

  1. Very insighteful article Jane. Foundations are . . . well . . . the foundation. And in So. California where the earth can move under ones feet, this is good information to know. You present a very calm and non-alarmist way of looking at foundation cracks.

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