BUR Membranes
BUR (Built-Up Roofing) involves melting of kegs/bricks of asphalt and using mops to apply that asphalt in between a base sheet, ply sheets, and a cap sheet. Ply sheets and additional layers of asphalt can be added until you reach the desired thickness. The finish layer is often a cap sheet or a layer of gravel overburden.
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Asphaltic Commercial Roofing 101
Proven historical performance. Time tested durability. Asphaltic roofing products are a go-to material of choice for high end low-slope buildings. Learn more about asphaltic technologies and application techniques, as well as how to decide if asphaltic is the right roofing solution for your next project.
Benefits of GAF BUR membranes
Maximum waterproof protection
Superior strength
Robust physical strength and superior resistance to heavy roof traffic
UV degradation resistant
Can be capped with a reflective mineral surfacing to efficiently resist harmful UV degradation
What’s the difference between SBS, APP, and BUR?
| Characteristics | Built-Up Roofing (e.g. GAFGLAS® BUR) | APP Modified Bitumen (e.g., RUBEROID® APP) | SBS Modified Bitumen (e.g., RUBEROID® SBS) |
| Weather Resistance | Provides maximum waterproof protection using alternating layers of asphalt roofing felt plies, typically capped with a high- performance BUR or SBS granulated cap membrane. | These membranes provide rigid, UV-stabilized weather protection and perform excellent in hot, sun-drenched climates. | These membranes act like synthetic rubber, exhibiting outstanding flexibility, allowing them to bend without breaking during extreme temperature drops (with service ranges as low as -20°F). |
| Durability | The multiple layers offer robust physical strength and superior resistance to heavy roof traffic. When capped with a reflective mineral surfacing (EnergyCapTM), BUR systems can efficiently resist long-term harmful UV degradation. | Designed primarily for torch-application, creating a monolithic, highly bonded roof surface that withstands weathering. | Excellent tear and puncture resistance. These systems are highly effective when applied using hot asphalt or cold-applied adhesives. |
How GAF BUR membranes are installed
GAF built-up roofing membranes are installed by “building up” multiple layers of asphalt and reinforcing felts on the roof, allowing contractors to tailor the system to project requirements and desired protection levels. Most BUR systems use hot asphalt to bond the layers, but compatible cold-applied adhesives and hybrid configurations may also be available depending on the specification. Watch the video for an overview of installation practices and options for GAF asphaltic roofing systems, including BUR, SBS, and APP membranes.
Related Built Up Roofing blog articles
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Built-Up Roofing (BUR) is a time-tested, highly redundant system featuring alternating layers of reinforcing felt plies and asphalt topped with a protective cap sheet or aggregate flood coat. Designed for low-slope applications, BUR provides exceptional weather protection, long-term leak resistance, and optional reflective surfaces to improve energy efficiency.
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Torch-down roofing utilizes an open flame to melt modified bitumen membranes directly onto the roof substrate, creating a seamless, watertight bond. Discover the key benefits, safety protocols, and ideal applications for this reliable, heat-welded installation method.
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Built Up Roofing membrane FAQs
BUR (Built-Up Roofing) is one of the oldest roofing techniques. It involves the melting of kegs/bricks of asphalt in a large metal kettle and using mops to apply that asphalt in between a base sheet, ply sheets, and a cap sheet. Ply sheets and additional layers of asphalt can be added until you reach the desired thickness. BUR systems are typically built on the job site, whereas mod-bit system membranes are manufactured in a factory and delivered, ready-to-install, to the job site. In lieu of cap sheets, some jobs are finished with a layer of gravel overburden — often referred to as a flood coat and gravel topping — over the last layer of asphalt.
APP and SBS modified bitumen are typically applied as a single cap sheet over a complete roofing system, while BUR comprises alternating layers of asphalt roofing felt plies, typically capped with a high-performance BUR, APP, or SBS granulated cap membrane.
Durable and long-lasting, GAF mod-bit roofing systems are eligible for No Dollar Limit guarantees up to 35 years for qualifying systems, where BUR systems are typically eligible for guarantees from 10-20 years. See the Commercial Roof Warranty Comparison Guide for details.
BUR system installation involves melting kegs/bricks of asphalt in a large metal kettle and using mops to apply that asphalt in between a base sheet, ply sheets, and a cap sheet. Ply sheets and additional layers of asphalt can be added until you reach the desired thickness. BUR systems are typically built on the job site. In lieu of cap sheets, some jobs are finished with a layer of gravel overburden — often referred to as a flood coat and gravel topping — over the last layer of asphalt.
Roofs that experience heavy foot traffic, severe weather or require high fire resistance are good candidates for a BUR roofing system. Typical applications include warehouses, factories, office complexes and retail malls with regular roof access that require long-term durability.
Durable and long-lasting, GAF mod-bit roofing systems are eligible for No Dollar Limit guarantees up to 35 years for qualifying systems, where BUR systems are typically eligible for guarantees from 10-20 years. See the Commercial Roof Warranty Comparison Guide for details.