Asphalt Roofing Systems

Built-Up Roofing

Built-up roofing (BUR) is a generic term for a roof system that is literally installed by building up layers of roofing material.  This is one of the oldest ways of installing a flat roof.  BUR comes in two basic types: asphalt and coal tar. There are three basic components: waterproofing, reinforcing and surfacing used to protect the other components from the elements. Surfacing for these rolled materials can consist of a smooth surface, mineral granules, aluminum, copper or an aggregate such as gravel or slag set in hot asphalt.  BUR material can consist of bitumen-saturated felt, coated felt, polyester felt or other fabrics. When BUR is covered with pea-sized gravel or slag, the roof is often referred to as BURG (Built-URoof with Gravel) or Tar & Gravel.  BUR can also be surfaced with asphalt, emulsion, or a granule-surfaced cap sheet.

As the product offering within the roofing industry has expanded, fewer consumers are installing these products, as many single ply systems now rise above this category in price and value analysis.

Modified Bitumen

Modified bitumen, often referred to as Mod Bit, generally uses a traditional waterproofing medium -- asphalt -- modified with atactic polypropylene (APP), styrene butadiene styrene (SBS), synthetic rubber, or other agents that will enhance the asphalt properties. APP and SBS are the most common bitumen modifiers.  These systems consist of one, two or three ply systems. The type of substrate will often determine the type of system installed.  A modified bitumen membrane is composed primarily of polymer-modified bitumen reinforced with one or more plies of fabric such as polyester, fiberglass, or a combination of both. Factory surfacing, if applied, includes mineral granules, slag, aluminum, or copper. Modified membranes can also be installed in conjunction with built-up roof materials (such as multiple plies of fiberglass felt) to form a "hybrid" roof system.