Red Seal Concrete Finisher Practice Exam

What is the typical thickness of a concrete slab for residential construction?

1. 2 inches

2. 4 inches

3. 6 inches

4. 8 inches

The correct answer is: 4 inches

In residential construction, a typical concrete slab thickness is commonly 4 inches. This thickness is generally sufficient to support the loads from typical residential structures without risking cracks or structural failure. When building foundations for homes, a 4-inch slab is also practical for providing adequate thermal mass and helping with insulation in various climates. While there are instances where a thicker slab might be required—such as in areas with heavy vehicle loads or where soil conditions necessitate additional support—4 inches remains the standard for most single-family homes. Thinner slabs, such as 2 inches, may not provide the durability or strength needed for flooring, while 6 inches or 8 inches would be excessive for standard residential applications and often used in commercial projects or where additional strength and load-bearing capacity are necessary.