Built-Up Roofing (BUR) for Commercial Flat Roofs

 Built-up roofing (BUR) is a proven low-slope roofing system made from multiple layers of asphalt/bitumen and reinforcing felts, finished with gravel surfacing or a cap sheet. It’s a durable, time-tested option for larger commercial buildings where redundancy and long-term protection matter. 

Built-up roofing is often called a “multi-ply” roof because it’s built in layers. Those layers work together to create a thick, resilient waterproofing membrane—ideal for low-slope commercial roofs that need dependable protection. BUR systems are commonly finished with either:

• Gravel surfacing (tar-and-gravel)
   
• A mineral cap sheet (smooth or granulated finish)

BUR gets its strength from redundancy—multiple layers that back each other up. While exact assemblies vary by building and spec, a typical BUR system includes:

• Roof deck (structural base)
   
• Vapor barrier (when required)
   
• Insulation (for energy performance and slope package)
   
• Base sheet
   
• Multiple plies of felt/fabric + asphalt/bitumen
   
• Surfacing (gravel or cap sheet)
   

Image #2 (diagram / infographic style)

• Graphic: Exploded “layer stack” diagram showing each layer labeled
   
• Alt text: “Built-up roofing (BUR) diagram showing multi-ply layers, insulation, and surfacing

 BUR is still specified today because it performs well in real-world conditions:

• Multi-layer leak resistance: Several plies create backup protection if one layer is compromised.
   
• Excellent durability: Thick assemblies can handle demanding roof environments.
   
• Strong UV/weather protection: Gravel or cap sheets shield the membrane from sun exposure and impact.
   
• Good for larger footprints: Often a fit for wide, low-slope roofs where long-term reliability is the priority.

Built-up roofing systems can be finished in different ways depending on performance needs and building use.

Gravel-surfaced BUR is the traditional tar-and-gravel system. The aggregate helps protect the roof membrane from UV exposure and physical wear, making it a durable option for many commercial buildings.

Cap sheet BUR uses a smooth or granulated cap sheet as the finished surface. This option provides a more uniform appearance while still delivering the layered protection BUR systems are known for.

 BUR is often a strong choice when you need maximum durability, a redundant multi-ply system, and a roof built to perform on large low-slope commercial buildings. The best way to confirm fit is a roof evaluation that considers drainage, existing conditions, insulation needs, and rooftop foot traffic.

• Request a Commercial Roof Inspection
   
• Get a BUR System Recommendation
   
• Schedule a Roof Condition Report
   

If you manage a commercial property and want a clear plan, we can inspect the roof, document current conditions, and recommend the best system for your building’s layout and budget.