General Contractor Houston Built Up Commercial Roofing
UNDERSTANDING LOW-SLOPE ROOFING SYSTEMS Very few people are experts on every kind of roofing system. However, the various types of low-slope roofing systems frequently considered for schools basically can be divided into two categories: multi-ply or single-ply. Multi-ply systems generally are bitumen-based (asphalt or coal tar), while single-ply includes polymer and metal systems. Several factors should be considered when selecting a roofing system. The installation design, its application and potential problems are important when determining the optimum system for a particular building. Another consideration is the environment. Although there are no nationwide programs to recycle roofing waste, some materials can be recycled or put to use in other ways.
BUILT-UP Description: Historically, built-up roofing (BUR) systems are the most common low-sloped roofing type. These systems are built-up from alternating layers of roofing felt and asphalt or coal-tar. It is these alternating layers that provide redundancy in these roofing systems. The reinforcing felts of yesterday were made from recycled rags and paper or asbestos. Today, the vast majority of these roofs use fiberglass as the reinforcing felt. These roofs function by using felt to reinforce thin, uniform layers of bitumen, which make the system waterproof. BUR systems commonly are referred to by the number of layers of roofing felt that are overlapped, the most common being 3-ply or 4-ply roof systems. Thus, in a 4-ply roof, there are a minimum of three films of waterproofing bitumen, depending on the method of membrane attachment to the substrate and the top coating used. In most cases there will be upwards of five films of bitumen in a 4-ply roof. The felt provides the strength to resist thermal and other rooftop stresses. The system is adhered to the top of an insulation layer, or to a base sheet, that is attached to the roof deck.
Ideal Application: Owner-maintained facilities commonly use built-up roofing because these roofs can be maintained by trained in-house staff. Repair materials are readily available, and the techniques are not difficult to master. Built-up roofs are reasonably abuse-resistant and difficult to vandalize.
Potential Problems: The odors from the hot bitumen during installation can cause concerns with building occupants and neighbors. Today, there are fume-control kettles available that greatly reduce fumes and odor. As with all roofing systems, inspection is recommended during the roof installation process, rather than the alternative of taking completed roof samples to check that correct amounts of materials were used.
