Commercial Built-Up Roofing (BUR)

What Is Built-Up Roofing (BUR)?

Let’s See if Built-Up Roofing is the Right Choice for Your Commercial Building

Built-Up Roofing FAQ

What are the Main Benefits of a Built-Up Roof?

• Exceptional durability: The multi-ply design creates built-in redundancy; a puncture, cut, or abrasion on the top layer is highly unlikely to penetrate all subsequent layers of bitumen and felt.   
• Superior waterproofing: When hot asphalt is mopped between plies, it creates a monolithic, seamless membrane across the entire roof field. This continuous surface eliminates the need for joints or seams in the main roofing area, which are the most common points of failure in many other commercial roofing systems.
• High puncture and impact resistance: The aggregate or mineral surfacing acts as a durable armor for the roof membrane. It provides excellent protection against damage from hail, falling branches, dropped tools, and other impacts that could easily puncture a less robust system.
• Excellent for high foot traffic: The combination of the multi-ply membrane and the hard surfacing makes BUR exceptionally resistant to the wear and tear of regular maintenance traffic. This is a critical advantage for commercial buildings with significant rooftop mechanical or solar equipment.
• Class A fire resistance: The gravel or mineral aggregate surfacing is non-combustible, giving BUR systems a high degree of fire resistance. This is a crucial safety feature that can help lower insurance premiums and provide peace of mind.
• Proven UV protection: The surfacing layer effectively blocks harmful ultraviolet radiation from reaching the underlying waterproofing bitumen. This protection prevents the asphalt from drying out, cracking, and degrading prematurely, which is a primary factor in the system’s long service life. 

What are the Known Disadvantages or Challenges with BUR Systems?

• Heavy weight: BUR systems are substantially heavier than their single-ply counterparts. This added dead load may require a structural analysis by an engineer to confirm that the building’s frame and deck can safely support the weight, potentially adding cost and complexity to the project.
• Complex and labor-intensive installation: The process of building up multiple layers is slow, physically demanding, and requires a high level of skill and attention to detail from the roofing crew.
• Odors and fumes during installation: The traditional hot-applied method involves heating asphalt in a kettle, which releases strong, pungent fumes. These odors can be disruptive to building occupants and may require special ventilation considerations or scheduling the work during off-hours, particularly for sensitive facilities, like hospitals or schools.
• Difficult leak detection: When leaks occur, they can be harder to locate because water may travel between multiple layers before becoming visible. This can make troubleshooting and repairs more complex and time-consuming. However, GSM offers infrared roof inspections that can help locate the trapped moisture.
• Susceptibility to ponding water: Like all low-slope roofing systems, BUR is vulnerable to the effects of ponding water — water that remains on the roof surface for more than 48 hours.

How Much does a Built-Up Roofing System Cost?

BUR systems typically have a higher upfront cost than single-ply options. However, their long lifespan and low maintenance needs often make them more economical over time.

BUR costs vary based on:

• Number of layers (plies): more ply layers = more material and labor
• Surface finish: gravel, smooth coating, reflective surfacing, etc. add cost
• Accessibility: how easy is the commercial roof to reach, work on, etc.
• Roof size and shape: bigger, simpler roofs usually cost less per square foot; complicated geometry or penetrations increases cost
• Removal vs. overlay: tear-offs increase cost
• Local code: Energy or fire codes can affect cost

How Long does a Commercial Built-Up Roof Last?

A professionally installed BUR system has an average expected service life of 20 to 30 years. Its longevity depends on factors, such as the number of plies, climate, proper drainage, and how well the roof is installed and maintained.

What Maintenance does this System Require?

Commercial BUR roofs are low-maintenance but should be inspected at least once or twice a year for signs of cracking, blistering, or ponding water. The roof surface, drains, scuppers, and gutters should be cleared of leaves, branches, and other debris to help prevent clogged drains.

Routine roof maintenance can extend the lifespan and prevent costly repairs.