If the frost line is 24 inches below the surface, which statement about footing depth is correct?

If the frost line is 24 inches below the surface, which statement about footing depth is correct?

• A. Above frost line
• B. Below frost line
• C. 24 inches below surface
• D. 12 inches below ground surface

Answer: (B)

Footings must be placed below the frost line to resist frost heave. The frost line marks how deep the ground freezes in winter, and keeping the foundation beneath that frozen layer prevents movement and cracking from freeze-thaw cycles. If the frost line is 24 inches below the surface, the footing needs to be deeper than 24 inches. Placing it above the frost line risks frost-related damage, while placing it right at 24 inches or only 12 inches would not stay below the freezing zone. So the correct statement is that the footing depth is below the frost line.

Footings must be placed below the frost line to resist frost heave. The frost line marks how deep the ground freezes in winter, and keeping the foundation beneath that frozen layer prevents movement and cracking from freeze-thaw cycles. If the frost line is 24 inches below the surface, the footing needs to be deeper than 24 inches. Placing it above the frost line risks frost-related damage, while placing it right at 24 inches or only 12 inches would not stay below the freezing zone. So the correct statement is that the footing depth is below the frost line.