Asphalt shingles typically provide the greatest advantage regardingwalk-ability. They provide a lightweight, relatively even surface to walk on and they rarely crack, break or become unfastened from the roof deck. They are less expensive to apply in relationship to other productsof similar performance. The overall manufacturer's design, cut, and production process, along with the weight of the material, determines the price of the roofing product. The labor installation cost for asphalt is similar among contractors because the product isgenerally applied the same. Asphalt shingles also provide the greatest variety of colors. However, because they are a petroleum-based product, the shingles can become scuffed if walked upon in the hot summer heat. Precautions shouldbe taken to protect the granulated surface while working on the roof structure in hot weather. Currently in Santa Clara County, asphalt shingle installations comprise about 70% of all roof replacements.