What does a "positive drainage" design in a BUR system achieve?

A "positive drainage" design in a Built-Up Roofing (BUR) system is fundamental for the effective management of water on the roof surface. This design ensures that the slope of the roof directs rainwater and any other forms of precipitation toward designated drainage points, such as drains or gutters. By doing so, it significantly reduces the risk of water pooling on the roof, which can lead to various issues such as leaks, structural damage, and the degradation of roofing materials over time.

This drainage system is crucial because standing water can contribute to the growth of mold, algae, and other organisms that can harm the roofing material and overall structure. Moreover, water pooling can increase the weight load on the roof, exacerbating structural concerns. Therefore, a positive drainage system not only enhances the longevity and reliability of the BUR system but also promotes the overall health of the building by mitigating water-related problems.

Thus, option B accurately describes the primary function and benefit of a positive drainage design in a BUR system.