Ask the Architect

A challenge in the Georgia clay

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Q. We’re planning a home in Georgia, and our contractor is telling us we can have a basement only if our house is more out of the ground instead of underground. It’s a hilly plot, so we want to exit from the basement in the back, but they keep telling us there’s a problem because the ground is clay and expands when it gets wet. They said the concrete walls will crack, and they won’t do the job the way we want. Have you ever heard of this, and if so, isn’t there some way to build what we want?

A. I’m reminded of the Rolling Stones lyric, “You can’t always get what you want,” but I also remember that the rest of the lyric is, “But if you try sometimes, you get what you need.” I’ve heard of these conditions, and many parts of our country have vast areas of expansive clay, where the ground is like putty. The problem with clay soil is that it’s so much denser, with little or no air space and no way to expand without forcing everything around it to expand and move as well.

You can certainly have a basement, but the work to create it would involve expert design techniques and a lot more excavation. The reasons it’s discouraged are cost, which most people would balk at; effort, which, for enough money, you can get a builder to do; and responsibility, which nobody wants, even after being assured that the work can be done. The area of excavation would require digging back and removing the clay to as far as four feet from the foundation. The soil below the foundation would require a new base of drainage material, up to 12 inches deep, with drain cloth to prevent clogging. A waterproof membrane would have to be placed under the new floor slab, continuous with the foundation walls, like the liner of a large swimming pool. The concrete foundation walls would need to be engineered to resist potential horizontal forces of the ground; backfilling would have to involve using foundation drain pipe and drainage fabric to allow the rainwater and groundwater to drop when it reaches the foundation wall; and soil away from the structure would need to be a sand mix for complete draining.

On Long Island, we’re spoiled because we have good-draining soil in many areas, although farther inland the soil may need to be remediated where there’s dense clay or rocky materials. So you can have a basement, but you’ll face an uphill battle. Even your local building department, not familiar with an idea that goes against their common practice, may need to scrutinize the architect’s or engineer’s design to be sure that something different is going to work. It’s tough being the first on the block to do something. Just be sure that trained professionals are guiding you.

© 2017 Monte Leeper. Readers are encouraged to send questions to yourhousedr@aol.com, with “Herald question” in the subject line, or to Herald Homes, 2 Endo Blvd., Garden City, NY 11530, Attn: Monte Leeper, architect.