Residential Building Inspector B1Footings and FoundationsMedium
An inspector is checking the grade around a new residential foundation. The finished grade slopes away from the foundation. According to the 2021 IRC, what is the minimum slope required for the finished grade for the first 10 feet from the foundation?
- A2 inches in 10 feet
- B6 inches in 10 feet
- C1 inch in 5 feet
- D12 inches in 10 feet
Show answer & explanationAnswer & explanation
Correct answer: B. 6 inches in 10 feet
IRC R401.3 specifies that the finished grade shall slope a minimum of 6 inches in the first 10 feet away from the foundation.
Why the other options are wrong
- A. Incorrect. This slope (2 inches in 10 feet) is insufficient to ensure proper drainage away from the foundation.
- C. Incorrect. This slope (1 inch in 5 feet, or 2 inches in 10 feet) is insufficient to ensure proper drainage away from the foundation.
- D. Incorrect. While a 12-inch slope would be effective, it is steeper than the minimum required by code.
Finished Grade Slope
The minimum downward incline of the ground surface immediately adjacent to a foundation, designed to direct surface water away from the structure.
- IRC R401.3 specifies drainage requirements.
- Prevents water from pooling against the foundation.
- Protects against moisture intrusion and hydrostatic pressure.
- A crucial component of exterior drainage.
Memory trick: Six inches in ten feet, that's the grade's sweet treat to keep water from your feet.