Custom Home411: Dealing with Expansive Soils (Yazoo Clay)

About the Author

Henry Moreau, began his homebuilding career in 1986 as a carpenter working for one of the last “working homebuilders”, Ted Peagler of Morton MS. From “Mr. Ted” he learned the importance of attention to detail, an acquired a working knowledge of the basics of fine homebuilding. From there he spent several years working for Harrell Construction, and developed a detailed knowledge of structural wood framing. In 1996, he hired a crew and launched his own frame carpentry company, later incorporated as Moreau Building Contractors. By 1998 he had passed the State Board of Contractors exam and was licensed as a residential builder. “One of the problems I started noticing as a general contractor was that I don’t think anyone ever brought me a stock plan and said, this is it, its perfect, don’t change a thing. Field modifications can be made, but too often they are not the best solution to the clients needs; a redesign would be needed to be most effective. The idea of doing design-build was appealing to me early on.” By the year 2000, Mr. Moreau had begun to study residential design in earnest. “All of the college texts I acquired stressed the importance of understanding how buildings are actually put together, and advised spending some time in the construction field to acquire that knowledge.” As energy efficiency came to the forefront of the homebuilding industry, Henry realized that the combined effects of designing for a particular site and personally attending to details was having a huge impact on energy efficiency in a cost effective way.

Dealing with Expansive Soils (Yazoo Clay)

Yazoo Clay is a common term used to describe what engineers would call soils with small particles and high plasticity, and therefore a great propensity to expand and contract due to changes in moisture content. Much of what is referred to as foundation problems is actually an underlying soil problem.

As I alluded to in the previous article, the usual recommended practice when these expansive soils are present is to excavate the entire footprint of the building, plus an extra 5-7 feet, to a depth sufficient to import enough non-expansive soils to leave a 5-7 foot buffer between the bottom of the foundation footing and any expansive soils. The imported soil must be properly compacted to avoid settlement. This process can be quite expensive, as much as $10/square foot.

This is the process I have used for years, with a steel matted monolithic slab, and have had no problems from the foundation. However, I have recently learned that problems can still arise from the soil.

When a house I completed a couple of years ago evidenced some relatively minor yet annoying cracks in the drywall and brick, the owners and I agreed that a third party consultation with an engineering firm was warranted. What we discovered was that the home was experiencing a bit of heave from deep underlying expansive soils, primarily due to some off lot drainage issues that the local municipality had never corrected. We have been assured the issue can be corrected with a subsurface drain, and that the structure of the foundation is sound. The importance of water management around foundations where expansive soils are present was really driven home to me.

In talking with the engineer from this company (Structural Solutions) I was impressed with not only the knowledge and experience, but the integrity they displayed. I was a bit leery at first, thinking that since they sell foundation repairs, they would naturally find them necessary. It was a relief for all to know the problem was not as serious as we feared it might be, and satisfying to know there are still businesses that will be honest even when it means the fix they sell you is only a fraction of what it could have been.

This level of integrity gave me a comfort level when looking into their pier system for dealing with expansive soils. From what I have found so far, the use of deep piers rather than soil replacement may save a couple of thousand dollars on the project I’m about to start. And they offer a warranty as well, which the owner can upgrade from a five year to a ten year or lifetime warranty for a nominal upcharge.

Stay tuned, as I should have some video of these piers being installed as we proceed with this project.