What is the maximum allowable backfill height for a plain masonry foundation wall of 8 feet tall according to the prescriptive requirements?

The maximum allowable backfill height for a plain masonry foundation wall of 8 feet tall, as dictated by the prescriptive requirements, is set at 5 feet 6 inches. This limitation is crucial for ensuring the structural integrity of the masonry wall. Exceeding this height can impose excessive lateral pressures on the wall, potentially leading to failure or damage.

Plain masonry walls are not designed to handle significant lateral loads that come from backfill, especially when the height of the backfill increases. The prescriptive requirements are in place to address these concerns by providing a guideline that helps ensure safety and stability. Therefore, limiting the backfill to 5 feet 6 inches helps to mitigate the risks associated with excessive lateral forces that could compromise the strength of the wall and the overall stability of the structure built above it.