TABLE OF CONTENTS All BURs share three basic components: felts, bitumens, and protective caps. The felts, asphalt-impregnated, fiberglass-reinforced membrane sheets are designed to act in concert with the bitumens (a semi-solid asphalt or coal tar pitch material) to create a moisture-resistant surface. The cap, weathering-grade asphalt embedded with mineral granules or gravel to protect the built-up roof from the elements is the third element in this assembly.
Built-up roofs can be subdivided into three categories:
Smooth surface BUR without any gravel topping. These roofs are lightweight, easy to inspect, and, if leaks occur, make it simple to determine the source of the leak.
Gravel surface BUR with a stone-aggregate spread over its entire surface after a flood coat of bitumen as been applied to protect the membrane from the elements. Gravel-surfaced BURs are limited to those roofs with slopes of 3 inches or less.
Mineral surface BUR with a top sheet of weathering-grade asphalt embedded with mineral granules to protect the surface from the elements.
Fluid-applied roofs can be installed with either hot or cold materials. This type of roof installation requires a stable substrate, such as a cast-in-place concrete deck. When applied over concrete, which must meet certain moisture content standards, a prime coat is first sprayed or rolled on. This is generally followed by the installation of a nylon or fiberglass mat mopped directly onto the primed concrete surface after which a top...
