Alabama Contractors License Practice Exam

Footings are not required to extend below the frost line when the monthly mean temperature of the area is ____ degrees Fahrenheit.

1. 56

2. 62

3. 64

4. 68

The correct answer is: 56

Footings are designed to provide stability to structures by transferring loads to the ground below. In regions where frost can penetrate the ground, footings typically need to extend below the frost line to prevent damage from frost heave. The frost line is the depth at which the soil is expected to freeze, and this depth can vary based on local climate conditions. When the monthly mean temperature of an area is 56 degrees Fahrenheit, it indicates that the climate is consistently warm enough that the ground does not freeze. In such warmer climates, the threat of frost heave is minimal or nonexistent, which is why footings do not need to extend below the frost line. The requirement for footing depth is primarily a measure to prevent structural damage caused by freeze-thaw cycles. Areas with higher mean temperatures, such as 62, 64, or 68 degrees Fahrenheit, may experience frost less frequently, but they are still at a higher risk of frost penetration compared to a region with a mean temperature of 56 degrees Fahrenheit. Therefore, under these warmer conditions, local building codes or practices may still require footings to be placed below the frost line, emphasizing the correlation between frost line depth requirements and average temperature.