What is the minimum exterior strip footing width?

• A. 250 mm
• B. 200 mm
• C. 350 mm
• D. 300 mm

Answer: (A)

The width of a strip footing is chosen to spread the wall load over enough soil so the bearing pressure stays within what the soil can safely carry. For exterior strip footings in typical residential construction, 250 mm provides a reliable minimum that gives enough bearing area without wasting concrete.

Choosing 200 mm would usually be too narrow for exterior walls, risking higher bearing pressures and potential settlement. Wider options like 300 mm or 350 mm are not necessary to meet the minimum requirement; they are used only when soil conditions are weaker or heavier loads demand larger footings. So 250 mm is the standard minimum that fits common building practices and soil conditions, with adjustments only if soil tests say otherwise.