North Carolina Building Contractor License Practice Exam

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What is the required thickness for a polyethylene vapor retarder placed between the base course and concrete slab?

4 mil
6 mil
8 mil
10 mil

The correct answer is: 6 mil

The required thickness for a polyethylene vapor retarder placed between the base course and the concrete slab is established to effectively prevent moisture from migrating upward into the concrete. A 6 mil thickness is the standard specified in most building codes and guidelines, including those relevant to North Carolina. The thickness plays a crucial role in ensuring durability and providing an adequate barrier against moisture, which can lead to potential issues like mold growth or damage to the concrete structure. Using a thicker material, such as 8 mil or 10 mil, may indeed enhance the barrier properties, but it often exceeds the minimum requirements set by building standards. Conversely, a thickness of 4 mil is generally considered insufficient to provide proper moisture resistance in most construction scenarios. Therefore, the 6 mil thickness is recommended for a balance of effectiveness and practicality, making it the correct choice in this context.