Bruttell Roofing

Historically, built-up roofing (BUR) is the most popular roofing system here in the US and has been around for more than 100 years. It received its name due to the multiple layers built from the bottom layer up, forming the functioning roof system. Each layer is formed with bitumen and felts/fabrics. Bitumenⁱ is the weatherproofing agent and also serves as the adhesive that reinforces each membrane layer. The multiple layers are highly resistant to heavy traffic and in some instances have been known to last for more than 50 years. A BUR that performs over twenty years is considered excellent. The surface of a BUR includes aggregate (gravel or mineral granules), hot mopped asphalt over the entire surface, and aluminum coatings. There are two types of bitumen: coal tar and asphalt.

Coal tar was in abundance where steel was being manufactured and was a by-product of the coal manufacturing industry. It has unique characteristics of healing itself in heat because of it’s chain linked molecules that “roll” over themselves, resealing its defects. However at temperatures below 53 degrees Fahrenheit, coal tar pitch acts like a crystal and is very brittle. It will crack when stressed in the winter with the weight of snow but re-heal itself in the warmth of the summer. Leaks that appear in the winter will disappear in the summer. The major issues with coal tar are its lack of availability, it’s messy application, the hazardous fumes, and its harm to the environment and the installers.

Asphalt is a product of the distillation of petroleum. It is pliable in warm temperatures and durable in colder temperatures. BURs are threatened by the harmful UV rays of the sun unless protected by a slag aggregate or a reflective coating. The sun will breakdown their composition causing them to fail prematurely.