Slope & Drainage Grade Calculator

Grading for Drainage in Grayson County

Kentucky receives 45–50 inches of annual rainfall, with heavy spring rain events common in Grayson County. Proper site grading is essential to direct water away from foundations, crawl spaces, and building footprints. The minimum recommended grade away from a foundation is 2% (1/4 inch per foot) for the first 6–10 feet. Steeper is better — 5% to the point where the grade transitions to a natural swale or drainage path.

Common Grade Reference Points

• Foundation grading: 2% minimum, 5% recommended
• Residential driveways: 1–5% grade (up to 12–15% for short steep sections)
• Parking areas: 2–5% for drainage
• ADA accessible ramps: Maximum 8.33% (1:12 rise:run)
• Gutters: Minimum 1/16" per foot fall (0.5% grade)

For site grading on new construction, deck installations, pole barn projects, or any landscaping that affects drainage near a structure, UIR evaluates the existing grade and drainage pattern before finalizing the design. Poor drainage is the root cause of most crawl space moisture problems and foundation damage. Contact UIR for a site assessment in Grayson County.