Prevent Foundation Damage With a Controlled Watering Program

Why soil moves your house

Expansive soils act like a sponge. As they absorb water they swell, and as they lose water they shrink. Soils tend to dry out and shrink during the summer, and to absorb water and swell during the winter and spring. As the soil under a house shrinks and swells with the seasons, the house moves up and down with it.

As long as that movement is not great enough to damage the house, most people do not consider it a problem. If the up-and-down movement always returns the house to its original level position, damage may appear and disappear on a regular basis as the seasons change.

If you want to stop seasonal damage, the first course of action should be a controlled watering program. By keeping the moisture content of the soil under the house constant, foundation movement can often be stopped.

How to water correctly

The goal is to maintain a constant level of moisture in the soil under the house. The best way to water is to place a soaker hose 12 to 18 inches from the edge of the foundation.

Placing the hose a short distance away allows the water to soak into the soil evenly. The hose should not be placed against the foundation. When soil has dried and cracked, water can travel along those cracks for several feet in all directions. If the soil around the foundation is dried and cracked, water placed right next to the foundation will run down and accumulate at the bottom of the grade beam — the thick portion of the foundation under the exterior walls.

In some cases an accumulation of water at the base of a foundation can cause the soil to lose some of its load-bearing capacity. If it loses enough, the house will sink into the ground.

How much, and how often

It is necessary to water more during hot, dry weather and less during cold, damp weather. The amount of water required to keep a foundation stable during a South Texas summer can be surprisingly large.

A single large tree can remove as much as 150 gallons of water — almost 20 cubic feet — from the soil each day. Shrubs and other plants also pull large quantities. During persistent hot, dry weather it may be necessary to water a foundation daily.

Watering should supply enough water to keep the moisture content in the soil under the foundation constant. If the amount applied is only enough to keep the surface damp, the watering program will not work.

Obviously, the homeowner is the only one who can weigh the benefit of controlling foundation movement against the increased size of the water bill.