Definition
Finish grade is the final ground surface elevation after grading and site preparation are complete. It establishes the drainage pattern, walkways, driveways, and landscaping surfaces. The finish grade should slope away from buildings at a minimum of 2-5% (1/4 to 5/8 inch per foot) to prevent water intrusion. Finish grade is typically set after all underground utilities and foundations are complete.
Formula
For proper drainage, maintain a 2% minimum slope (1/4 inch per foot) away from foundations. A 5% slope is ideal for lawn areas. Over 25% is considered steep and may require retaining walls or special erosion control measures.
Example
Finish Grade Example
A house foundation is at elevation 100.0 feet. To achieve a 2% slope for proper drainage, the finish grade 10 feet from the foundation should be at 99.8 feet (100 - (0.02 x 10) = 99.8). This 0.2-foot drop equals 2.4 inches, providing adequate drainage away from the structure.