Surface Grading
With melted snow and the heavy rains we have already experienced this spring, it is critical for homes to have proper surface grading around their homes to prevent flooded basements.

There are three terms used to describe the drainage grade on the surface of the earth around a building: negative, neutral and positive. Negative means the grade of the earth has a downward slope toward a building that then delivers roof and surface water directly to the foundation. Neutral means the grade is level and does not direct water toward a foundation, but can still cause water to pool next to a foundation. Positive means the grade has a downward slope away from a building to prevent water damage.

Improper surface grading‹negative or neutral‹can create hydrostatic pressure in the earth next to foundation walls and underneath concrete slabs and basement floors. The pressure can cause water to seep through cracks and holes in foundation walls and seep up through joints or cracks in cement floors. Moisture vapor can also pass through solid concrete walls and floors where it immediately enters indoor air. The result is excessive humidity that contributes to mold contamination on building materials and personal property.

Improper grading is considered a defect in need of correcting. To achieve a proper grade, the earth around a building should gradually slope down and away from a building for at least 10 feet, dropping a minimum of half an inch per foot. This means the soil 10 feet from the building should be five inches lower than the soil next to the building. By the way, according to siding manufacturers the height of the soil starting at the building should be four to eight inches below the bottom edge of the siding. From the 10-foot point, flatwork or a swale in the earth should carry water toward a field or storm sewer. This is considered the minimum drainage grade acceptable.

In most improper grade conditions, dirt can be added to achieve an acceptable grade. In situations where a building was initially constructed too low in the earth, adding more dirt could cause soil/siding contact damage, which could lead to insect and rodent infestation, mold growth inside walls, and rotting of structural framing. Therefore, a landscaper must excavate soil away from farther out in the yard to achieve a proper grade.

Landscaping materials, whether mulch or stone, allow water to pass through them. Only the earth underneath constitutes the actual grade. If there is any question as to proper grade, the landscape materials should be removed temporarily, soil should be added or removed as needed to attain a proper grade, and then the landscape materials can be replaced.

Improper grading can also cause emergency sump pumps to run frequently, which can cause premature pump failure, resulting in flooding when the pump is needed most. A sump pump system should only operate during extreme weather conditions and should never be considered a solution for improper surface grading.

Flat surfaces like sidewalks, driveways and patios, should also slope away from a building and should never be allowed to act as a dam, holding water next to a building.

This article is copyrighted and reprinted with permission by DanSchilling and Home Resource Magazine. To receive a copy of Home Resource, contact Sarah Schilling at publisherhr@gmail.com.

This article is intended to be general in nature and is not intended to address all potential issues. Specific determinations must be obtained by qualified experts.