What is the primary purpose of using stone on a Built-Up Roof (BUR)?

The primary purpose of using stone on a Built-Up Roof (BUR) is to protect the roof system from weathering and damage. By adding a layer of stone, the roof gains a robust covering that acts as a barrier against various environmental elements, including ultraviolet (UV) radiation, hail, and wind. This layer significantly extends the service life of the roofing materials underneath by preventing deterioration caused by exposure to the elements.

Additionally, the stone ballast helps to secure the roofing membrane in place, minimizing movement and potential damage from wind uplift. It also adds fire resistance and helps in regulating the temperature of the roof surface, further enhancing the durability of the BUR system.

In contrast, while aesthetic appeal may be a consideration, it is not the primary function of the stone. Electrical insulation is not a relevant factor for stone used on BURs, as the purpose of roofing materials usually revolves around waterproofing and protection rather than insulation properties. Lastly, reducing the weight of roofing material does not align with the typical use of stone, as stone is generally added for its protective characteristics rather than for weight reduction.