Construction Supervisor License Practice Exam

When installing a sand base course for a slab below grade, it is typically recommended to use a thickness of around 4 inches. This thickness provides adequate support for the concrete slab above, contributing to proper drainage and reducing the risk of moisture-related issues.

A 4-inch sand base helps to distribute the load of the slab evenly over the subgrade, minimizing settling and cracking. Additionally, this thickness is effective for allowing for proper compaction and creating a stable layer that promotes good performance of the slab. The sand also acts as a capillary break, which is crucial to prevent water from seeping into the concrete from the underlying soil, thus ensuring the longevity and durability of the slab.

Thinner layers, such as 2 inches or 3 inches, may not provide sufficient support or drainage capabilities, potentially leading to structural issues. A thicker layer, such as 6 inches, may be unnecessary and can lead to additional costs and labor without significant benefits. Therefore, a 4-inch sand base is both a practical and effective choice for a slab that is below grade.