Footings must extend how far below undisturbed soil or properly compacted fill?

The depth of footings is crucial for ensuring the stability and safety of a structure. In Virginia, the building codes specify that footings must extend a minimum of 12 inches below undisturbed soil or properly compacted fill. This requirement is in place to prevent issues like settling, shifting, or frost heave, which can lead to structural problems.

The 12-inch depth ensures that the foundation is anchored in stable soil, providing adequate support for the weight of the building above. This depth also helps to mitigate the effects of freeze-thaw cycles in colder climates, where a deeper footing can prevent frost from causing the soil to expand and contract, which can lead to cracking and damage to the foundation.

The other options—8 inches, 10 inches, and 14 inches—do not meet the minimum requirements set forth in the building codes, as 8 and 10 inches are insufficient to ensure the stability needed for safe construction, while 14 inches exceeds the typical requirement without a specific justification such as extreme frost conditions or unique soil issues.