The Greater Houston Area largely consists of soils that exhibit some expansive characteristics related to the clay content in the soils. Because changes in moisture content in these soils across a foundation can result in differential movement in a building’s foundation, it is important to maintain the moisture content uniformly. This is typically done through control of the influence of vegetation such as large trees with root barriers, maintaining positive drainage away from foundations, and through a watering program.
I am frequently asked if a yard sprinkler system can be used to help maintain the moisture content of the soil around a building, most often a home, to maintain the performance of the foundation. The answer is that a yard sprinkler can be effective in some cases but more often it is not run enough to be effective at preventing some seasonal differential settlement in a foundation due to soil drying, which can affect interior finishes. Most sprinkler systems for the yard are run just a few times a week, which can keep the grass alive but may not keep the soil moist enough to prevent shrinkage at the perimeter of the building. This moderate drying of the soil may affect foundation performance. It is often a better solution to install a dedicated watering system for the foundation that can be run for several short intervals daily for the most effective use of water and to prevent damage to the yard from over watering.
Dedicated foundation watering systems vary widely in design. They can be as simple as the common black porous hose you can lay out on the ground or a commercially installed drip system. In the past French drain style systems have been used and have been effective. They can be independent of an existing yard sprinkler system or they can be part of that system if the controller will accommodate the needed variations in schedule, and if there are enough zones to accommodate the needed system. The goal is to create a moist boundary of soil around the foundation to insure a uniform moisture in the soil supporting the foundation across the building. There is an added benefit to a foundation watering system in that they are typically not regulated as a yard watering system and can be operated when the yard system cannot; however, you need to confirm this with your local authority during periods of drought and water restriction.