Tar and gravel roofing, also known as built-up roofing (BUR), has been the go-to flat roof technology for decades.
A tar and gravel roof, or built-up roofing, consists of several layers of waterproof material alternated with hot tar and a surface layer of mineral aggregate, often smooth river stone. This surface layer weighs down the built-up roof, protects it from sun exposure, and serves as decoration. There are a wide variety of materials available for each layer.
The purpose of the gravel is to shield the asphalt from the damaging effect of sun exposure. It also provides a nice finished appearance if well maintained. The life expectancy of such a roof is 20 years.
Types of Built Up Roofing
There is Smooth Asphalt built up (Hot or Cold), and Ballasted Asphalt built up. The bitumen material commonly used in built-up roofing systems is asphalt, coal tar or cold-applied adhesive. The surfacing and materials used on built-up roofing are so varied and depend entirely on your project and its budget. Ballasted asphalt is being used more regularly than before because it can provide an excellent finish surface and its material is a better fire retardant agent. There is also Cold Built-Up roofing that, instead of requiring hot asphalt for its application, can be sprayed or applied with a squeegee.
Advantages of Tar and Gravel Roofs
Proven time-tested system - it has been around for over 100 years
Very durable - gravels or minerals can be used as surfacing material
Weather resistant - It lasts longer to weather inclemency
Low maintenance and easy to repair
Built-up Roofing provides ultra-violet protection and excellent waterproofing protection