North Carolina Building Contractor License Practice Exam

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What is the purpose of placing a polyethylene vapor retarder under concrete slabs?

To enhance finish quality
To prevent moisture migration
To improve structural integrity
To assist in curing

The correct answer is: To prevent moisture migration

The purpose of placing a polyethylene vapor retarder under concrete slabs primarily revolves around preventing moisture migration. This barrier is critical in controlling the movement of moisture from the ground into the concrete, which can lead to a variety of issues such as efflorescence, mold growth, and deterioration of flooring materials. By installing this vapor retarder, contractors can effectively safeguard against moisture-related problems that can compromise the integrity and longevity of the flooring system. In terms of construction practices, moisture control is essential, particularly in residential and commercial buildings where flooring finishes, such as carpets and laminates, may be adversely affected by excessive moisture. This measure ensures that the moisture level beneath the concrete slab is kept in check, contributing to a healthier indoor environment and maintaining the quality of the construction over time.