North Carolina Building Contractor License Practice Exam

What must concrete block walls be free from before applying weep screeds?

1. Moisture

2. Efflorescence

3. Cracks

4. Dust

The correct answer is: Efflorescence

The correct answer is that concrete block walls must be free from efflorescence before applying weep screeds. Efflorescence is a white, powdery substance that appears on the surface of concrete and masonry materials when water evaporates and leaves behind soluble salts. If efflorescence is present, it indicates moisture and potential water movement through the wall. This can interfere with the adhesion and effectiveness of the weep screeds, which are designed to allow moisture to drain out of the wall system. Applying weep screeds over surfaces affected by efflorescence could lead to further moisture retention and damage over time. While it's important for concrete block walls to be managed concerning moisture, dust, and cracks, those factors do not specifically indicate the need for removal like efflorescence does. Dust can generally be cleaned off without significant impact on the application process, and while cracks must be addressed to ensure structural integrity, they do not directly affect the weep screeds in the same manner as efflorescence.