A typical basement is constructed of a footing or footer that supports the basement walls and floor. The footing must rest on solid or undisturbed soil. The wall may be constructed of cement block, poured concrete, brick, stone or tile. In the past 80 years, most foundation walls have been constructed of cement block or poured concrete. The floor is poured concrete supported on the edges by the footing and in the center by compacted gravel.
These cracks, typically due to drying shrinkage, thermal movement or other causes usually are minor and result in few problems. More often than not, a foundation crack will widen over time and result in water seepage or possibly the loss of structural integrity. Foundation and slab cracks are not only an eyesore, but they may hinder the value of the home.
Cracks can be signs of an overload or excessive stress on a wall. As homes get older, cracks have a better chance of appearing. Excessive displacement, continuing movement, differential settlement and certain combinations of cracks are real problems we will discuss. The exception – those little hairline cracks that appear in floors and walls – often are caused by shrinkage and are not a concern since they are just cosmetic in nature.
What distinguishes a minor crack from a major problem? The key often is the amount of wall movement. Any movement over 1/2 inch signals a potentially serious problem. Any long horizontal crack at the second or third mortar joint, under the top block or over the bottom block, combined with step cracks and inward movement, indicates a problem. While step cracks near windows and corners often are not serious, if they are combined with floor cracks, shear or vertical cracks, you should be concerned.
Most builders would agree that water leaking into the basement is a common warranty issue. Homeowners and builders are continually looking for ways to utilize every square inch of potential living space. As a result, basements are frequently being converted into useable space. Thus, designing to keep basements dry is more important than ever.
A Crack can be injected with polyurethane for less money or if the crack never stops flowing and is constantly wet. The problem with polyurethane in a small, hairline crack is that when polyurethane activates, it creates air bubbles. In fact, most polyurethane expands to over 10 times their original size! So when a hairline crack is injected with polyurethane, the net result is a boat load of air bubbles and a small amount of polyurethane between you and the great outdoors which may be fine for a large crack or rod hole, but not for a standard foundation crack.
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