A common option for flat or low-sloped roofs, especially in commercial and industrial structures, is a tar and gravel roof. A layer of stone or gravel is used to support the several layers of hot tar or asphalt that make up this roofing method. In addition to providing UV protection for the tar, the gravel also adds weight to assist shield it from wind damage. An superb waterproofi... https://managemyroof.com/tar-and-gravel-roof/