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Roofingaka: BURaka: tar and gravel roofaka: built-up roofing

Built-Up Roof (BUR)

In Plain English

A flat roof system built up from multiple layers of asphalt and felt, topped with gravel — the classic commercial flat roof.

Definition

A traditional flat or low-slope roofing system consisting of multiple alternating layers of bitumen (asphalt or coal tar) and reinforcing fabrics (felts or plies), topped with aggregate surfacing or a cap sheet. BUR systems have been used for over 100 years and are valued for their durability, redundancy, and resistance to foot traffic. They are installed by moppers or mechanical applicators that spread hot bitumen between layers.

Why It Matters in Bidding

BUR systems are labor-intensive and material-heavy, so the number of plies, type of bitumen, and surfacing all drive a roofing bid's cost and crew composition. Hot-applied work also carries safety, kettle, and fume-control requirements that must be priced, and tear-off of an existing aggregate BUR adds significant disposal weight and cost.

Example

A roofing estimator bidding a warehouse reroof prices a four-ply BUR with gravel surfacing, then adds tear-off and dumpster line items because the existing aggregate-ballasted roof must be removed down to the deck before the new plies go on.

Related Terms

Cap SheetModified BitumenFlashingVapor Barrier

Frequently Asked Questions

Pricing is driven by the number of plies, bitumen type, surfacing, and square footage, plus crew labor for hot application. Estimators also account for kettle setup, flashings, and edge metal. More plies increase redundancy and cost, so the spec'd ply count must be confirmed before pricing.
BUR is more labor-intensive and slower to install than single-ply membranes like TPO, often raising labor cost, but it offers redundancy and foot-traffic durability. When a spec allows alternates, contractors may bid both and let the owner weigh upfront cost against expected service life and maintenance.
Tear-off of aggregate-surfaced BUR generates heavy debris, driving up disposal tonnage and dumpster costs. Hot-work also requires fume management, fire watch, and kettle logistics. Wet or damaged decking discovered during tear-off can trigger change orders, so a unit price for deck replacement is wise to carry.

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