The minimum depth of a footing shall extend ... A -

The minimum depth of a footing shall extend ... A -

• A. 12 Inches
• B. 18 Inches
• C. 24 Inches
• D. Below the Frost Line

Answer: (D)

The depth of footings must go below the frost line to prevent movement from freeze-thaw cycles. When the ground freezes, soil heaves and can lift a footing that sits in frozen ground. By placing the footing deeper than the depth to which the soil freezes (the frost line), the foundation rests in unfrozen soil and remains stable as temperatures vary. The exact frost line depth depends on climate and soil, so local code defines the required depth. The fixed depths (12, 18, or 24 inches) may be above the frost line in colder regions and too shallow to prevent frost heave, so they aren’t reliable universal requirements.

The depth of footings must go below the frost line to prevent movement from freeze-thaw cycles. When the ground freezes, soil heaves and can lift a footing that sits in frozen ground. By placing the footing deeper than the depth to which the soil freezes (the frost line), the foundation rests in unfrozen soil and remains stable as temperatures vary. The exact frost line depth depends on climate and soil, so local code defines the required depth. The fixed depths (12, 18, or 24 inches) may be above the frost line in colder regions and too shallow to prevent frost heave, so they aren’t reliable universal requirements.