A bituminous coating must protect fiberboard wall insulation applied on the exterior of foundation walls located _____ ground level.

A bituminous coating is utilized to provide moisture protection for various construction materials, particularly in scenarios where those materials might be subject to water exposure. When fiberboard wall insulation is applied on the exterior of foundation walls, it is crucial to ensure that it is adequately protected from potential water intrusion, which is more likely to occur below ground level due to surrounding soil moisture and groundwater.

Installing fiberboard insulation below ground level exposes it to direct contact with moisture, which can lead to deterioration, loss of insulation value, and increased risk of mold growth. The bituminous coating serves as a waterproof barrier, preventing moisture from penetrating the insulation and the foundation wall. Therefore, it is essential that this protective coating be applied specifically to fiberboard wall insulation when it is positioned below ground level to ensure durability and maintain the integrity of the building’s thermal envelope.

Other options, such as above or at ground level, imply different conditions that do not necessitate a bituminous coating for moisture protection to the same extent as below ground level, where the risk of water damage is significantly higher.