Rainy stretch can leave mark on foundations

By Bill Garwood

For the AJC

After the heavy rains of the last month or so, many homeowners have experienced not only water entry into basements and crawl spaces but also structural problems with their foundations. Although it takes an experienced professional inspector or structural engineer to determine structural issues, homeowners can look for a few signs.

Based on when your house was built, foundations in Georgia are typically built with one of four materials: brick, concrete block, stone, and poured concrete. Each reacts differently to changes in soils that support them.

Here are some guidelines for checking your foundation.

Brick: Brick foundations are either piers (stacks of brick spaced apart) or continuous (solid brick walls). Brick foundations were not typically used in North Georgia after the 1940s. If you have a brick pier foundation you should examine the piers individually for evidence of erosion of the mortar between the bricks. A good rule of thumb for determining excessive erosion of mortar is one-quarter inch or greater. If you have erosion of a quarter inch or more, you should consider repointing (installing new) the mortar. Also, look for leaning of the brick piers. If some or all of the piers are leaning you should consider consulting a professional engineer or a foundation repair contractor.

If you have a continuous brick foundation you should look for cracks in the foundation walls. Cracks will be either horizontal, vertical, diagonal, or step type (stepping down through the mortar joints). In many cases, especially with cracks one-eighth inch or less in width, or cracks that have been in the foundation for a long time, step cracks will have resulted from previous settlement and are not a structural problem. However, if the step cracks are wider or are new you should consult with an engineer or foundation repair contractor. The same rules apply for vertical or diagonal cracks. If the cracks are less than one-eighth inch wide and are not new they may not signify a current structural problem. Horizontal cracks are potentially the worst type of cracks.

Stone: Stone foundations were common in North Georgia through the 1950s. As with brick, look for cracks. The most common type of cracks found in stone foundations are step type cracks. If the cracks have gotten noticeably larger, you should consult with a registered engineer or foundation repair contractor.

Concrete block: Concrete block foundations were commonly used from the 1940s into the 1980s. In my experience, concrete block foundations are the most susceptible to problems due to excessive water in the soil. Again, as with brick and stone, you should examine your foundation walls for cracks. Vertical and step cracks that are not new and have not changed are likely not a problem. Horizontal cracks, however, are very often the direct result of soil pressure against the house and are often a structural problem. Especially in houses with below-ground basements, look for horizontal cracks in the top third of the foundation wall.

Poured concrete: Poured concrete foundations have been used since the 1930s but have become the most commonly used foundation type in the last 20 years. The most common type of cracks found in poured concrete foundations are vertical or diagonal. These cracks indicate some settlement in a portion of the foundation. If during your inspection you notice a crack that is new or more than a “hairline” (very thin) crack you should consult with a professional. If your house is constructed on a concrete slab you should examine the edges of your slab for cracks. Also, walk through your house with bare feet. Sometimes this is the only way to feel cracks through carpeting or vinyl flooring. You also should look for any cracks in tile or other hard flooring. If you find cracks consultation with a professional engineer or foundation repair contractor is recommended.