North Carolina Building Contractor License Practice Exam

How shall the grade be sloped away from a building for drainage?

1. 1:30

2. 1:20

3. 1:10

4. 1:5

The correct answer is: 1:20

The correct answer is that the grade should be sloped away from a building for drainage at a ratio of 1:20. This means that for every 20 units of horizontal distance, there should be a 1-unit vertical drop. This slope is generally recommended because it provides adequate drainage to direct water away from the foundation, minimizing the risk of water pooling near the building, which can lead to structural damage over time. A 1:20 slope is a balanced approach that encourages effective runoff while being manageable for landscaping and construction purposes. It is essential to maintain a slope that is neither too steep nor too shallow. If the slope is too steep, such as in the 1:10 or 1:5 range, it could lead to erosion issues and create an unstable foundation around the building. Conversely, a slope that is too gentle, like 1:30, may not effectively direct water away from the foundation, increasing the risk of water damage. Therefore, a 1:20 slope is considered the appropriate standard for ensuring efficient drainage while protecting the integrity of the building structure.