Seasonal water intrusion is typically seen near foundation areas. Causes include poor grading, uncontrolled roof runoff at downspouts or lack of a gutter system or poorly adjusted lawn sprinklers among other possible sources. The bottom line is that water needs to be controlled and diverted away from foundation walls.
A proper slope away from the foundation is essential to keep water away. The minimum required grade for new construction is a slope that falls at least 6 inches in 10 ft. Usually soils are back filled near the foundation area and will settle over time, especially if its poorly compacted.
Roof runoff is water that falls off the roof during rain storms or snow melt. A gutter system helps collect this water and discharges it to one or more downspouts. As one can imagine, a significant amount of water can discharge at a downspout, especially during heavy rain. Therefore, it is important to install downspout extensions or splash blocks to divert roof runoff away from foundation areas at least 18 inches. The grade needs to be at least the minimum standard described above in order to continue to divert water away from the foundation area.