What is the minimum footing width on solid rock?

What is the minimum footing width on solid rock?

• A. 24 inches
• B. 15 inches
• C. 12 inches
• D. 16 inches

Answer: (C)

The width of a footing is set to provide enough bearing area for the load, based on the strength of the supporting material. On solid rock, the rock itself can carry heavy loads, so you don’t need a wide footing. A 12-inch width is the commonly accepted minimum, giving enough bearing area and room for reinforcing while staying practical. Wider footings (like 16, 15, or 24 inches) are only needed for heavier loads, larger walls, or special conditions, not for the minimum on solid rock.

The width of a footing is set to provide enough bearing area for the load, based on the strength of the supporting material. On solid rock, the rock itself can carry heavy loads, so you don’t need a wide footing. A 12-inch width is the commonly accepted minimum, giving enough bearing area and room for reinforcing while staying practical. Wider footings (like 16, 15, or 24 inches) are only needed for heavier loads, larger walls, or special conditions, not for the minimum on solid rock.