Footings below undisturbed ground surface must extend at least how many inches?

Footings below undisturbed ground surface must extend at least how many inches?

• A. 12 Inches
• B. 6 Inches
• C. 18 Inches
• D. 24 Inches

Answer: (A)

Footings must extend below the depth that freezing soil can reach to prevent frost heave from moving the structure. Extending the footing at least twelve inches below undisturbed ground surface places it below the active frost zone in many climates, which is why a twelve-inch minimum is the standard. Local codes adjust this depth based on climate and soil conditions, so in very cold areas or with certain soils you may need more depth. A shallower footing, like six inches, risks movement from frost, while deeper depths are required only where frost depth or bearing conditions demand it.

Footings must extend below the depth that freezing soil can reach to prevent frost heave from moving the structure. Extending the footing at least twelve inches below undisturbed ground surface places it below the active frost zone in many climates, which is why a twelve-inch minimum is the standard. Local codes adjust this depth based on climate and soil conditions, so in very cold areas or with certain soils you may need more depth. A shallower footing, like six inches, risks movement from frost, while deeper depths are required only where frost depth or bearing conditions demand it.