Grading For Positive Drainage
The fill around your house should be dense clay soils and properly compacted with grading to slope away from your house at least 5 percent for a minimum of 10 feet, making the ground 6 inches lower than the ground surface at the house wall. This will drain surface water away from the wall and help prevent water from standing against the wall and potentially seeping through it or causing water pressure under the basement floor. Planting and mulching around outside walls should be done carefully to preserve drainage away from the wall.
To help prevent surface water from standing in your yard, don’t create or maintain a perfectly flat space. Maintain a slight slope that drains toward a swale, rain garden or storm sewer inlet. If you can’t do this, some type of underground pipe and gravel drain with a sump may be necessary. Even very well-drained soils may become saturated in a Virginia summer thunderstorm, so try to maintain a slope of 5 percent away from the house and 2 percent everywhere else.