California Residential Inspector Practice Exam

In what manner should the upper layer of water-resistive barriers be applied over the lower layer?

1. Vertically

2. Horizontally

3. Alternately

4. Perpendicularly

The correct answer is: Horizontally

The upper layer of water-resistive barriers should be applied horizontally over the lower layer. This approach is crucial because it ensures proper water shedding and helps prevent water from penetrating through potential gaps or seams in the barrier. When the upper layer is installed horizontally, it creates a more effective overlap with the lower layer, allowing any water that encounters the barrier to flow over the seams rather than being directed into them. Applying the upper layer horizontally also aligns with standard building practices that prioritize drainage and moisture management in wall assemblies. This configuration helps maintain the integrity of the barrier and provides a more effective defense against moisture intrusion, which is particularly important in residential construction in areas prone to rain and water exposure.