California Residential Inspector Practice Exam

A slab-on-ground concrete floor must have a minimum thickness of how many inches?

1. 2 inches

2. 3 inches

3. 31⁄2 inches

4. 4 inches

The correct answer is: 31⁄2 inches

The minimum thickness for a slab-on-ground concrete floor is established in building codes to ensure structural integrity and durability. A thickness of 3½ inches is common practice, providing sufficient strength to support loads from structures and resident usage. This thickness is generally regarded as a standard that balances the material use with the necessary strength for typical residential applications. Thicker slabs can lead to unnecessary material costs, while thinner slabs may not provide adequate support, especially under heavy loads or in areas prone to soil movement. Therefore, the 3½-inch specification is established to minimize issues such as cracking and settling while ensuring the slab does not use excess material unnecessarily. This thickness allows for the proper functioning of the concrete, ensuring adequate performance in normal residential conditions. In summary, a slab-on-ground thickness of 3½ inches strikes a practical balance between durability, functionality, and cost effectiveness in residential construction standards.