How wide should the footer be for a CMU wall?

• A. Twice the width of the block
• B. Equal to the depth of frostline
• C. Equal to the width of the block
• D. Three times the width of the block

Answer: (A)

A CMU wall needs a footing that distributes the load over a larger soil area to prevent settlement and cracking. Using a footing that is twice the width of the block gives ample bearing surface beyond the wall edges, helping to keep the wall stable under its weight and any backfill. The width is a horizontal dimension chosen to spread load, while frost considerations apply to how deep the footing sits below grade, not how wide it is. So, a wider footing equal to the block width would be too narrow, and making it three times the block width is typically more than necessary for ordinary walls.