February 2006

Not all foundation cracks are cause for concern

In my more than 30 years of constructing and inspecting homes, some of the most frequent questions I get from homeowners concern cracks in foundations, interior walls, brick veneer siding and driveways, sidewalks or patios. The following is some information to help you determine the seriousness of foundation cracks. Since they are often related to foundation problems, in coming weeks we will explore cracking in brick veneer siding, interior walls and ceilings and exterior concrete surfaces.

Foundations

Foundations in Georgia are typically one of four types: poured concrete, concrete block, brick or stone. Not all cracks in these materials are problematic. Some cracks are the result of natural expansion and contraction or the curing of the masonry or concrete. Since foundation repair can be expensive, the trick is to determine when the crack is severe enough to require a repair.

There are three basic types of foundation cracks: horizontal cracks, vertical cracks and step cracks. Of these three types, horizontal cracks tend to be of most concern.

Horizontal cracks

Although horizontal cracks are found in poured-concrete, brick and concrete-block foundations, they are most common in concrete block and brick. Often horizontal cracks result from excessive pressure on the foundation from soil that has become wet. The soil around the house usually becomes wet as a result of poor drainage from the roof and the ground around the house. If you have a horizontal crack in your block, brick or poured-concrete foundation wall, perform the following test. Measure the width of the crack. Typically, cracks of 1/4 inch or more are considered severe. Also place a level against the wall perpendicular to the crack. If there is a bulge of more than 1/2 inch in the wall at the crack, this also indicates the crack is severe. Another indication of a severe crack is called differential displacement, which is when one side of the crack has been pushed in or out more than the other side, creating a ledge at the crack.

Vertical cracks

Vertical cracks are found in all types of foundations. Many vertical cracks are considered "hairline" cracks. A hairline crack is very small and the same size throughout its length. A vertical crack becomes worrisome when it is wider at the top than at the bottom. If the vertical crack goes all the way to the bottom of the foundation wall and appears to be in the footing as well, this is an indication of settlement and warrants further investigation and repair. This type of settlement is often caused by poorly compacted soil under the footing.

Step cracks

Step cracks are found in brick, stone and concrete-block foundations. Step cracks are so named because they follow the mortar joints of the foundation and end up looking like a set of steps. To determine if step cracks are severe, measure their width. Like horizontal cracks, if the crack is 1/4 inch or wider, further investigation and repair are warranted. Similar to vertical cracks, step cracks tend to be more severe if they are wider at the top than at the bottom. Also look for differential displacement in step cracks. When one side of the crack has moved in or out more than the other side, this is an indication of more severe movement.

If you have performed the above tests on your foundation wall and believe you have significant structural movement, you will want to take the next step or steps to resolve the problem. There are many foundation-repair companies that will assess your problem and perform a repair. These companies are easily found in the Yellow Pages.

Remember that foundation-repair companies are in the business of selling and making repairs. If you have any doubts about whether your foundation problem really is severe, you may want to take the additional step of consulting with a qualified, registered engineer. Because the engineer is paid to assess and design a repair for the problem — not perform the repair — he may be more objective in their analysis. In choosing an engineer, make sure you hire someone with expertise in residential structures.

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