- The grade or slope of the soil should be designed to direct surface water away from or around the home. Water accumulation next to the home can lead to water penetration problems such as structural damage to wood framing, interior damage to finished surfaces and damage to the homeowners’ belongings.
- Additional problems such as hydro-static pressure against foundation walls or surface water mixing with expansive soils next to or under a foundation can lead to cracking of the slab and foundation walls.
- Proper grading in conjunction with a gutter and downspout system is one of the easiest ways to manage surface water, reduce the possibility of water penetration and structural damage from hydro-static pressure, and control the water content in expansive soils.
Exterior Surface Grading
Grading of the Soil Around the Perimeter of the Home
- The soil around the perimeter of the home should slope away (at a minimum of six inches for the first 10 feet) from the foundation to prevent rain water from accumulating next to the foundation walls.
- Soil in this case does not refer to the top-soil but the layer of soil that is impervious to water such as clay, which directs the water away from the house. Many times the top-soil is porous (as would be used for planting) and absorbs the surface water.
- The sub-layer of clay or similar non-porous soil prevents the water from continuing in a downward movement and directs the water laterally. If non-porous soil next to the foundation slopes toward the house, water will begin to accumulate.
Grading of the Lot
- The overall lot grading is also an important concern since surface water may enter from adjacent properties. Generally, if the house is located on a slope or on a lot that receives water run-off, swales are often used to direct the water around the house.
Swales
- Swales are shallow ditches or depressions in the landscape that capture the water run-off. Then, like a small creek, the water is directed around and away from the house.