CSLB C-27 Landscaping ContractorSite Preparation and DrainageMedium
A landscape contractor is grading a site for a new lawn area. The design calls for a final grade that ensures positive drainage away from the adjacent building foundation. What is the minimum recommended slope for the first 10 feet away from the foundation?
- A2% (2 inches drop per 10 feet)
- B3% (3 inches drop per 10 feet)
- C1% (1 inch drop per 10 feet)
- D4% (4 inches drop per 10 feet)
Show answer & explanationAnswer & explanation
Correct answer: A. 2% (2 inches drop per 10 feet)
A minimum slope of 2% (or 1/4 inch per foot) for at least 10 feet away from a building foundation is widely recommended by building codes and landscape design standards. This ensures positive drainage and prevents water accumulation that could damage the foundation.
Why the other options are wrong
- B. While 3% would provide excellent drainage, it's not the minimum recommended, and can sometimes be too steep for aesthetic or functional purposes in a lawn area.
- C. A 1% slope is generally considered too flat for effective positive drainage away from a foundation and may lead to standing water.
- D. A 4% slope is typically steeper than necessary for basic positive drainage and might be used in specific situations but is not the minimum recommendation.
Positive Drainage Slope (Foundation)
The minimum slope required in grading adjacent to a building foundation to ensure water drains away from the structure, preventing moisture intrusion and damage.
- Prevents water accumulation near foundations.
- Standard recommendation is 2% for 10 feet.
- Critical for structural integrity and moisture control.
Memory trick: Two percent's the rule, keep water cool, away from the wall, preventing its fall.