The Best Repair Option for a Gravel Built-up Roof

Gravel built-up roofs (BUR) are among the most durable commercial systems, but when they age, their restoration requires a specific approach. Here's the best repair option.

Why Traditional Repairs Fail on Gravel BUR

The gravel layer makes leak detection difficult and individual repairs impractical on aging systems. Water can enter through a breach anywhere beneath the ballast and travel significant distances before appearing as an interior leak. Spot repairs rarely find all breaches.

The Best Option: Spray Foam After Gravel Removal

For aging gravel BUR roofs, spray foam restoration after hydro-vacuuming is consistently the best value. The process: hydro-vacuum gravel ($0.50–$1.00/sq ft), replace wet insulation, apply spray foam directly to the BUR substrate, and finish with a silicone topcoat. Total cost: $4–$7/sq ft with a new 10–20-year warranty.

Why This Works So Well

The existing BUR substrate — once gravel is removed — provides an ideal bonding surface for foam. The foam fills every crack, seam, and potential breach simultaneously, creating a completely new seamless surface. Every existing failure point is eliminated in a single application.

Compared to Alternatives

Full BUR replacement: $8–$14/sq ft. TPO over cover board: similar or higher cost, plus introduces new seams. Spot repairs: address individual failures but not system-wide aging. For most gravel BUR roofs, foam restoration delivers the best performance at the lowest long-term cost.