Coastal and Floodplain Construction Inspector's Practice Exam

What is the minimum thickness of asphalt felt used in a water-resistive barrier?

1. 15 lb

2. 30 lb

3. 60 lb

4. 20 lb

The correct answer is: 15 lb

The minimum thickness of asphalt felt used as a water-resistive barrier is typically recognized as 15 lb. This specification refers to the weight of the felt per unit area (in this case, per square foot), indicating the density and quality of the material. Asphalt felt serves as an effective barrier to moisture, preventing water from penetrating the structural components of buildings, particularly in coastal and floodplain zones where exposure to high moisture and water levels is common. The use of 15 lb felt is widely accepted in various building codes and construction standards, making it a reliable choice for applications where moisture control is critical. In contrast, heavier weights such as 30 lb or 60 lb asphalt felt are available and may provide additional protection in more demanding conditions, but they are not the minimum requirement established for standard applications. The mention of 20 lb is less common, thus reinforcing that the 15 lb felt is considered the baseline for effective moisture resistance in construction practices.