Built up roofing is a common commercial roofing application, and is the most popular materials used on low-slope commercial roofs. It is composed of several layers of bitumen surfaces and an aggregate coating. The layers used on built-up roofs are called ply sheets, which are typically reinforced with fiberglass or other organic mats depending on the type of built-up roof and climate.

Built up roofing comes in several different forms. The best alternative for your business roof depends on the anticipated use. The most common types of built up roofing are asphalt built up and ballasted asphalt built up roofs. These built up roofs use asphalt, coal tar or cold-applied adhesive as the bitumen material that comprise the commercial built up roof layers. Ballasted asphalt built up roofs have layers that are not anchored to the decking material but are instead ballasted by covering the layer with gravel. Ballasted asphalt built up roofs are often quicker to install and are more fire retardant than standard asphalt built up roofs.

Alternatively, cold built up roofing does not require hot asphalt and can be sprayed on or applied with a squeegee. Cold built up roofs do not have the toxic fumes that are common with asphalt-based built up roofing and are often used for environmentally sensitive commercial roof projects. Cold built up roofs are not weather dependent and can sometimes perform better than hot built up roofing.