There are two common mistakes landscapers make, costing homeowners big money every year in the Houston Metropolitan Area. These are the grading and the drainage of our property. The “gumbo clay” in the Houston area is an expansive clay soil mixture that must be properly maintained. If not, you could end up with foundation problems that cost anywhere from a few thousand dollars to over fifty thousand dollars. Each molecule of clay can expand up to 300 times its size when wet. This exerts an enormous amount of pressure on the foundation and is one of the main causes of foundation failure. Years of pressure cause the house structure to move and form cracks both inside and outside of the house. Preventive maintenance is key to keeping your home from having these kind of structural issues.
Grading Too High
Every year people mulch gardens next to the house because it creates a welcoming and pretty view. Unfortunately, having the soil up high against the house also creates a welcoming environment conducive to ants and termites. To protect your home, it is recommended that the soil is kept 4 inches below masonry and 6 inches below all other siding. If the soil line is kept at the same level around the house, it won’t hold water and moisture against the foundation unevenly. Keeping the grading below the siding also exposes the top of the foundation so it can be monitored for cracks that show movement in the home structure.
Negative Grading
The opposite problem is negative grading where the soil or grass angles down, toward the house instead of away from it. High amounts of mulch in the middle of the gardens can cause water to flow toward the home. Depressions in the soil where water sits for days is called ponding. Typical reasons for these areas are dogs digging, sprinkler systems spraying at the foundation, and not surrounding the house with gutters to move water away from the house. When a house doesn’t have gutters, or the gutters are full of debris, the rain pours off of the roof and creates an erosion line. Over time this line grows to hold the water against the foundation. Because Houston has so much rain, draining all that water is important. Homes need to be re-graded from time to time. The appropriate slope for the ground is a 6 inch drop away from the house over a distance of 10 feet (2% grade). Where there isn’t 10 feet between houses, a 3 inch drop will normally drain water away with graded swales.
Some people intend well when they put rocks next to the house. However, if the yard wasn’t properly graded away from the foundation before the rocks were added, it can unknowingly create a moat that holds & diverts the water underneath the foundation. When the perimeter dries out first and the soil underneath stays wet, this can cause the foundation to heave (push up in the middle) and crack.
Solutions
Professional landscaping contractors can design a solution for diverting the water away from your house. Properly placed gutters, swales, and subsurface drains are all good options to make sure your yard drains water properly. These are all helpful to make your house last a lifetime!