Materials needed to install hot tar roofing, otherwise known as built-up roofing, include enough felt to cover the roof several times, a hammer and nails, scissors, tar and a mop. Finishing a hot tar roof is optional, but if it is desired, a covering such as crushed granite is needed in a quantity that covers the roof. Alternatively, top the roof with metallic paint or a rubber plastic coating.
To install BUR, cut two 12-inch wide strips of felt that span the length of the roof. Nail one down near the edge of the roof to use as a starting point. Mop tar over the felt strip and place the other strip on top of it. Mop the entire length of the strip once more. Move along the roof, first creating rows with felt that overlap one another by 24 inches and mopping over them with tar; repeat this up to five times to create the desired thickness of the roof. To add a granite finish to the roof, add a final thick layer of tar and spread the granite across it.
The application of felt under the tar waterproofs the roof, which is one of the major advantages of a BUR. Additionally, a granite finish gives the roof a fire retardant quality. Unfortunately, BURs are incredibly heavy and sometimes require reinforcement of the roof's joists before installation. While it is the cheapest roof application, it is also the messiest, and in the event of a leak it is almost impossible to find the weakened area.