Built-Up Roofing (BUR)
Built-up roofing is a multi-layer flat roofing system constructed by alternating layers of bitumen (asphalt or coal tar) and reinforcing fabrics, topped with a gravel or mineral cap sheet surface.
Multi-Layer Flat Roof Protection
Built-up roofing (BUR) is a time-tested flat roofing system made by layering alternating sheets of bitumen-saturated reinforcing fabric and hot-applied asphalt, finished with a surface layer of gravel, mineral granules, or a cap sheet. BUR has been used on commercial and residential flat roofs for over a century. The multiple layers create redundancy: even if the top layer is compromised, the lower layers continue providing waterproofing. BUR is often called "tar and gravel" roofing for its distinctive surface.
BUR claims involve unique challenges around damage identification, tear-off costs, and estimating accuracy.
Damage Assessment on BUR
Identifying storm damage on a built-up roof is more difficult than on single-ply membranes or shingles. Hail impact on the gravel surface displaces aggregate and can fracture the underlying membrane layers, but the damage is not always visible from the surface. Core samples, which involve cutting a small section through all layers for examination, are sometimes necessary to confirm damage. Wind damage typically presents as lifted or displaced gravel, exposed membrane, and edge or flashing failures.
Document the gravel surface condition before and after the storm event if possible. Displacement patterns in the gravel can indicate impact locations.
BUR in Xactimate
BUR estimates in Xactimate require line items for each layer of removal and each layer of installation. The number of plies (typically 3 to 5) affects both removal and installation costs. Gravel removal and disposal is a separate line item. Because BUR is heavier than single-ply systems, structural considerations and disposal costs are higher. Make sure the estimate specifies the correct number of plies based on the existing roof system to avoid underpricing the tear-off and replacement.
Frequently asked questions
A well-maintained built-up roof can last 20 to 30 years. The multiple layers provide redundancy, so even if the top layer is damaged, the underlying layers continue to protect the structure. Regular maintenance extends the lifespan significantly.
BUR replacement involves removing multiple heavy layers, which increases labor and disposal costs. The multi-layer installation process also takes longer than single-ply membrane installation. Xactimate reflects these higher costs in the line item pricing.
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