For anyone who has grown up or lived in the south, you probably recognize that there are no basements there. This can be a confusing quirk to southern homes for those who have spent most of their lives up north. The reason why southern homes don’t have basements has a lot to do with engineering and how feasible they are to construct down south.
To begin this post, I want to make something clear. It is theoretically possible to build a basement virtually anywhere. Basements can be built in the south, but it is just too expensive and too much of a hassle to do for the reasons we are about to discuss.
Up north the terrain tends to have a lot less surface moisture. Down south, we have swamps, rivers, and lakes running through a large portion of land. For this reason, the water table in the south tends to be much closer to the surface, within 10 feet, than it is up north. When the water table is this close to the surface, building a basement essentially means you’re building a giant concrete well as the foundation of your house. The water either 1. seeps into your home’s basement and floods it or 2. causes your house to float. As any engineer likely realizes, neither of these options is beneficial in the longevity of home sustainability.
If you wanted to build a basement in a location with a high water table, you could by using a system of relief wells. Every time a well takes water from the ground, it has a conical effect on the surrounding water table called a “cone of depression.” On a side note, this also happens to be my favorite engineering technical term ever. This cone of depression drastically changes the water table around the center point where water is being pumped out. If a homeowner wanted to build a basement, all that would be needed is several relief wells around the house to draw down the water table in that area continuously. This is obviously very expensive and if the pumps break, then you have problems.
Other than the water table issue, the soil in the south tends to be more damp clay than up north. When the clay is damp, or dry, or whatever state it is in, it generally isn’t an issue to build on or construct a basement in as long as it stays that way. Problems occur when the clay particles transition between states. The clay in the south tends to be highly expansive, which causes massive deviation in the basement and thus the house’s foundation. Building a foundation within these expansive soils is typically a no-go in terms of cost-value added.
The last minor reason there are no basements in the south has to do with the frost line. For a building to maintain strength, its foundation should be below the frost line in the soil. In the north, the frost line tends to be much lower underground, so foundations have to be much deeper. For this reason, builders construct basements because they already have to dig down that deep for the foundation – adding a basement is of low cost. In the south, the frost line tends to be very close to the surface. There is no reason for builders in the south to build a basement because the foundation doesn’t need to be very deep anyway.
To summarize, engineers don’t build houses in the south with basements because we don’t want buildings to float, crack, or sink and because it adds too much unnecessary cost.