What is the primary function of crushed stone or gravel ballast on a built-up roof?

The primary function of crushed stone or gravel ballast on a built-up roof is to protect the roof from sunlight. This is crucial because the UV rays from the sun can degrade roofing materials over time, leading to deterioration and reduced lifespan of the roofing system. The ballast acts as a protective layer, helping to shield the underlying materials from direct exposure to sunlight and its damaging effects.

In addition to UV protection, the ballast also helps stabilize the roofing system, preventing movement and damage from wind. While aesthetics can be a consideration, the primary role of the ballast goes beyond appearance; it significantly contributes to the longevity and performance of the roof by protecting it from environmental factors. Other material functions, like insulation or water drainage, may be present in roofing systems but are not the primary purpose of the ballast layer.