What Is Built-Up Roofing (BUR)?

A BUR roof is assembled on the building in alternating layers. Plies of felt or fiberglass reinforcement are mopped in place with hot asphalt, coal tar, or a cold-applied adhesive, so each layer is sealed to the one beneath it. A typical roof has several plies, which gives it redundancy: one flaw does not open a path through the whole assembly. The top is protected by a flood coat of bitumen with gravel embedded in it, a mineral-surfaced cap sheet, or a reflective coating.

Plenty of older commercial buildings still wear BUR, and a rep calling on them will see gravel, blisters, and patched seams. Tear-off of a gravel roof is heavy, loud, and slow, and the choice between tearing off and covering over affects scope, disposal, and the building’s structural load. Leaks can be hard to trace because water travels between plies before it appears inside, so infrared scans and core samples are used to find wet insulation.

BUR is not obsolete just because newer membranes get more attention, and plenty of buildings are still re-roofed with it. Tar and gravel is slang, and the binder may be asphalt or coal tar, which handle differently and carry different fume and handling precautions. Gravel can blow or wash into drains, and it hides damage, so inspecting beneath it takes more than a walk across the surface.