How to Grade a Site for Drainage
How to establish finish grades that direct surface water away from structures and toward drainage outlets, preventing foundation and landscaping damage.
Step-by-Step
- 1
Establish the finished floor elevation
The finished floor elevation (FFE) is your starting reference. All site grades are established relative to it. Confirm the FFE from the architectural drawings and verify it against the benchmark elevation.
- 2
Determine required grades
The ground must slope away from all structures at a minimum of 6 inches over 10 feet (5%) for the first 10 feet per IRC. Beyond 10 feet, a minimum 2% slope is maintained to a drainage outlet. Mark all high and low points on a site plan.
- 3
Set grade stakes
Set grade stakes at the building perimeter and at regular intervals (every 25–50 feet) across the site. Mark each stake with the required cut or fill amount. Use a laser level to maintain accuracy across the site.
- 4
Rough grade with equipment
Use a motor grader or skid steer to move material from high areas to low areas. Work toward the drainage outlet. Leave 4–6 inches of room above final grade for topsoil. Avoid creating low spots or bird baths (ponding areas).
- 5
Compact filled areas
Any area that received fill must be compacted. Fill in lifts of 6–8 inches, compact each lift before adding the next. Uncompacted fill will settle unevenly and create drainage problems after the project is complete.
- 6
Apply finish grade topsoil
Spread 4–6 inches of topsoil over the rough-graded area. Rake smooth and confirm grades with the laser level. Finish grade must maintain the required positive drainage slope.
- 7
Stabilize the surface
Install sod, seed with erosion control blanket, or apply hydroseed immediately. Bare soil erodes rapidly. If seeding, water daily until germination and the grass knits together.
Pro Tips
- → Always grade so water has a clear path to an outlet — a storm drain, swale, or street. Never grade water toward a neighbor's property.
- → A laser level pays for itself on the first job. Eyeballing grade leads to drainage failures.
- → Check grades after a rain event before final stabilization — water will find any low spot you missed.
Watch Out
- ! Never direct drainage toward a neighboring property — it creates legal liability.
- ! Grading too close to a building foundation without proper drainage can cause hydrostatic pressure and basement leaks.