Built-up roofing is used primarily for roofs with no slope. This method of roofing has existed for more than 150 years and is an extremely popular solution for flat roofing. Built-up roofing is made up of multiple layers of roof felts alternating with layers of bitumen to create a finished membrane. These systems are often called "tar and gravel" roofs because a layer of gravel is applied over the asphalt layers to secure the membrane. Built-up roofing is a popular choice because it is the least expensive of the four main types of flat roofing materials. Drawbacks are that built-up roofing is heavy and not as easy to install as some of the lighter alternatives.
This rolled material can either be applied using heat or peel-and-stick methods. Modified bitumen is available in light colors that can also reflect direct sunlight and create a cool roof that will create significant energy savings for the home.
What is Bitumen?
Bitumen is a refined petroleum product, more commonly known as "asphalt." It is a strong and durable adhesive that binds together a wide variety of other materials without affecting their properties. Bitumen/asphalt is insoluble in water, it resists corrosion by most acids, salts and alkalis, and doesn't contaminate water. It is a thermoplastic material: it softens with the application of heat and hardens as it cools. It is available virtually the world over and is economical.