Site Grading or French Drains
Grading slopes away from the home — or french drains are installed (new construction).
Spec
Applies uniformly from Silver upward.
Scope
Site grading and subsurface drainage in new construction projects.
Requirements
Choose one path
- 01.
Grading path: site must be graded to slope away from the foundation at a minimum of 6 inches over the first 10 feet (6% slope), continuing to drop at least 2% beyond that.
- 02.
French drain path: where grading is constrained (urban sites, retaining walls, sloped lots), install a perimeter French drain at the foundation footing depth, connected to a daylight termination, dry well, or storm sewer.
Documentation
Evidence the inspector / Institute will need.
- 01.
Civil/grading plan stamped by the project engineer showing the slope profile.
- 02.
OR French drain detail drawing + photos of installation before backfill.
Guidance
Why the 6/10 rule
IRC R401.3 specifies the 6"/10ft (6%) minimum positive grade away from foundations. Below that slope, surface water sheets toward the foundation during heavy rain and saturates the perimeter soil. Above 6%, the slope is steep enough that water consistently drains away even on saturated ground.
Note
On urban infill lots where positive grading is impossible (e.g. neighbor's lot drops toward yours), French drains combined with a sump pump (interior or exterior) become the only practical solution. Plan for the sump pump in the electrical load at the climate-risk assessment stage.