In the real estate biz in Texas, we joke that there are two types of slab foundations: 1) those that need repair, and 2) those that have been repaired. As near-drought conditions worsen throughout the entire state of Texas, one of the key items homeowners need to pay attention to is how our slab foundations are holding up. In Texas especially where the soil has a high amount of clay, it’s important to make sure that you keep the moisture level the same around the entire house by using sprinkler systems or soaker hoses.
With clay soils especially, any sort of slab foundation is susceptible to moisture evaporating in the areas exposed to direct sunlight/heat. The clay soil under the house will absorb as much moisture as possible, which causes the middle of the house that’s not exposed to churn like the sea. The result is the soil under the house expanding and lifting the center up, causing the corners of the slab to fall. This causes foundation cracks, noticeable by cracks in the brick veneer outside, around windows and doors on the inside, and by making doors not line up with their strikeplates causing them not to close.
Homebuilders prefer to perform soil tests where we note the soil tensile strength and how much the soil will hold moisture. If that number is too high, we’ll drill down to see how far the bedrock (the solid layer of rock that sits below the topsoil) is from the surface of the foundation. By drilling holes and filling them with concrete reinforced with steel, we can then build the foundation so that it rests on the piers instead of the top of the soil. This ensures that the foundation stays steady and will not be susceptible to the churning of the soil under the house which leads to so many foundation settling issues. Houses can be retrofit by engineers to pour piers posto facto under the house, however this can be quite costly.
The best way to fight this is to keep the soil around the house moist all year round. Houses with sprinkler systems should have a series of sprinklers close to the house to accomplish this. However, the next best thing (possibly even better) is to dig a trench 4-8″ around the entire perimeter of the foundation that’s about 3″ deep and bury a soaker hose, covering the hose with soil after it’s laid. By running the soaker houses a couple times a week, you can ensure that the moisture levels will stay equalized and hopefully reduce the amount of settlement issues you have.
Finally, landscaping plays a very important role in keeping your foundation healthy. Houses are built on a raised pad so that drainage will flow around the house and not thru. Keep your grass around the house in good shape to eliminate washout of the soil around the house. In addition, plant shrubs around the house, and be careful not to plant trees closer than 10′ to the foundation. Roots from the trees will search out the most moisture, which happens to be from under the house. Those large roots aggressively on the move can contribute to the soil drying out or even crack the foundation themselves.
You can never eliminate settlement dangers completely, but by paying close attention to a few minor things, you can help mitigate unnecessary problems before they happen.
