It is pretty much common knowledge that the soils that underlay most houses in Central Texas are very moisture-sensitive clays. There are of course many different types of these clays but what they all have in common is their tendency to shrink when drying out and swell when taking on moisture. Most foundation problems are a result of this phenomenon.

Foundation distress from this behavior can be controlled by managing foundation soil moisture. Here the goal is to maintain near constant moisture around the perimeter of your home. This is an often-misunderstood issue, as many recommendations seem contradictory. For example, one recommendation suggests drainage corrections to aid in the rapid removal of water away from the foundation; another advises homeowners to apply water at the base of their foundation. Foundations, for the most part, would remain mostly stable if they were either: A. Wet all the time, or B. Dry all the time. While it is impossible to maintain dry conditions all the time, our only remaining option is to insure that these soils remain for the most part ideally somewhat damp. Recommended correction of drainage problems on the other hand is necessary to limit the amount of moisture accumulated during periods of prolonged rainfall. The same is true of Gutters and Downspouts.

During hot, dry weather, moisture needs to be added to replenish water lost through evaporation and use by plant material. This can be accomplished in a number of ways. For example, underground sprinkler systems can be modified to include a “Foundation Zone”, timed to apply the desired amount of water at the proper point automatically. Soaker hoses are an inexpensive solution to the distribution of water around a foundation. Enough soaker hoses should be purchased as to allow for coverage of the total perimeter to insure even distribution. Hoses can be either above or below ground and up to 10 to 12 inches away from the foundation. The operational time for the application of water will vary with the amount of current rainfall. Given the almost total absence of rain that we sometimes experience, a twice-weekly application on the order of about three or four hours, preferably during the evening, will reduce loss of water due to evaporation. Other conditions will require some judgment on the part of the homeowner. Do not, however, apply water to the point that it creates ponding of water or marsh-like conditions.

The soil drying effect of trees and shrubs often goes underestimated. Depending on size, trees common to our area can extract from a hundred to several hundred gallons of water from the soil per day – per tree! If they are not receiving this level of moisture from either rain or supplemental watering, these roots are migrating under your foundation to access the moisture typically present as a result of protection from evaporation by your foundation. The result being the deprivation of vital moisture your foundation's sub-grade requires. Root growth control can be achieved by pruning roots at the base of the foundation and by various root shield methods commonly available.

By recognizing that growing plants, along with hot, dry weather deplete soil moisture, and that replenishment moisture is available through various man-controlled methods as well as rainfall, it is feasible to reduce significant foundation movement through active moisture management of soil.

Southern/Austin, Inc., 9514 McNeil Rd., Suite 101, Austin, Texas 78758, Phone: 512-419-1600, Toll-free: 800-840-7989, Fax: 512-973-8679