Foundation Drainage Problems
The moisture levels in the ground surrounding and supporting your home greatly affects the stability of your foundation. If the soil is too saturated with water, the soil below can soften, swell, or erode. If the soil is too dry, it will compress, leaving pockets of loose soil and air beneath your home. This section will focus on the former foundation issue: too much water in the soil.
The moisture content in the ground under and around your home varies on the cyclical nature of the wet and dry seasons. In the rainy season, higher moisture content in the soil will cause it to expand, which adds extra lateral stress on your home’s foundation. Additional moisture in the soil also dramatically increases the hydrostatic pressure exerted on your foundation adding several thousand pounds of pressure per square foot. This, in turn, weakens the foundation walls causing cracks and eventual failure. Conversely, dry spells will weaken the soil’s structural integrity, causing the ground to recede and crack.
After a flood or a storm, large volumes of water rapidly enter the ground around your home. The moving water can erode the areas under your home leaving cavities of air which can no longer support the weight of a house. These empty spaces under your home will cause the foundation to eventually collapse into them causing cracks and settling.
Insuring Proper Damage
To avoid the previously-mentioned issues, water should always be directed away from your foundation. A quick way to detect whether your property is properly draining is to measure the decrease in your yard’s elevation as you move away from the foundation. A good rule-of-thumb is to have a five percent grade, or to have a 6-inch drop in elevation for the initial ten feet away from the foundation.
To measure this drop in elevation, take two stakes, a ten-foot length of string, and a ruler. Place one stake near your foundation, and the other 10 feet away in a straight line. Then, tie one end of your string to the stake near your foundation as close to ground level as you can. Tie the other end of the string to the far stake and make sure the run is level. Use your ruler to measure the distance between the ground level at the far stake and where the level string touches the stake. If the distance is at least six inches, you have an acceptable grade. If you have less, you’ll need to add fill dirt around the foundation and tamp it down.