Final grading around a new house before sod.

IRC R401.3 requires a minimum 5% slope (6 inches drop in the first 10 feet) away from the foundation.

Key details:

• Measurement: 6" vertical drop measured horizontally 10' out from the foundation wall.
• Impervious surfaces (patios, walks, driveways): Only 2% slope (1/4" per foot) required (R401.3 Exception).
• Swales: If lot lines/walls prevent 10' of slope, a swale/drain is required to carry water away (R401.3).
• Backfill: Must be free of organic material/debris, compacted in lifts to prevent settlement that reverses slope (R403.1.6).

Practical tips:

1. Establish rough grade before pouring flatwork so you hit the 5% on dirt and 2% on concrete simultaneously.
2. Compact the 10' zone thoroughly (mechanical plate compactor, not just track-walking). Settlement is the #1 callback.
3. Verify with a 10' straightedge and level (or laser/transit) before sod. A 6" gap under the level at 10' = pass.
4. Window wells/steps: Grade must still slope away; use drains in wells tied to footing drain.

Check local amendments. Some jurisdictions require 6% or 10' minimum impervious surface extension. Always confirm with the AHJ before final inspection.

Most residential building codes, including the International Residential Code (IRC), require a minimum slope away from the foundation to ensure proper drainage and prevent water intrusion.

IRC Section R401.3 states: > “The ground immediately adjacent to the foundation shall be sloped away from the building at a slope of not less than 5 percent (6 inches of fall in 10 feet) for a minimum distance of 10 feet measured perpendicular to the foundation wall.”

If physical obstructions (like property lines, walls, or slopes) prevent achieving the full 10-foot slope, the code allows an alternative: > “Where lot lines, walls, slopes, or other physical barriers prohibit 10 feet of horizontal distance, a 5 percent slope shall be provided to an approved alternative method of diverting water away from the foundation.” (IRC R401.3 Exception)

Key practical points for sod installation:

• Ensure the subgrade is compacted and graded to this slope before placing topsoil and sod.
• Topsoil should be uniform (typically 4–6 inches deep) and not alter the intended slope.
• Avoid creating low spots or depressions near the foundation where water can pool.
• Downspouts should extend at least 5 feet from the foundation (IRC R801.3) and discharge onto graded surfaces, not directly into the soil near the wall.

Note: Always check local amendments — some jurisdictions may require greater slope (e.g., 10%) or longer distances, especially in expansive soil or high-rainfall areas. When in doubt, consult your local building department or a licensed civil engineer/landscaper. Improper grading is a leading cause of basement leaks and foundation damage.