One of the most commonly utilized commercial flat roof systems is modified bitumen roofing. Modified bitumen (MB) roofing systems are asphalt-based and closely related to Built-up-Roof (BUR) systems.  They are designed as a solution for buildings featuring low slopes or flat roof structures. Modified bitumen roofing membranes date back to mid-1960s Europe and have been successfully implemented throughout the United States and Canada since 1975.

This roofing system is uniquely designed to withstand harsh environments and exposure to extreme natural elements. Featuring five layers of protection, modified bitumen flat roofing systems are among the most trusted in the industry.

Advantages of Modified Bitumen Roofing

Modified bitumen roofing has become widely adopted due to the numerous benefits it provides over other roofing systems. Some of its most significant advantages include:

  • Waterproof and leak-resistant
  • UV and heat resistant
  • Exhibits high tensile strength and tear resistance
  • Weather-resistant and compatible with fire, hail, and wind-rated roofing systems
  • Available with VOC-free and flame-free installation
  • Environmentally friendly
  • Simple installation process

Modified bitumen roofing systems deliver a highly competitive life cycle cost compared to alternatives. Additionally, it can be applied using several methods, making it adaptable to the needs of diverse environments. Modified bitumen roofs feature an average lifespan of 20 years or more with proper maintenance. It is also one of the most amenable roof styles for repairs.

Varieties of Modified Bitumen Roofing

Modified bitumen roofing systems are available in two varieties:

  • SBS membranes. Styrene-butadiene-styrene (SBS) roofing membranes are comprised of asphalt mixed with polymerized rubber for added flexibility. More elastic and less brittle in cold weather, SBS-modified bitumen is installable on hot, non-modified asphalt. It is typically recommended for structures featuring roofs that contract and expand due to extreme temperature changes.
  • APP membranes. Also referred to as plastic asphalt, atactic polypropylene (APP) membranes are asphalt mixed with plasticized polymers that require high temperatures to become elastic. While less elastic than SBS bitumen, APP-modified bitumen features a superior UV and temperature resistance and is frequently chosen to add a cool roof effect to structures. It cannot be installed using a hot mopping technique as it cannot bond properly using this method.

Modified Bitumen Roofing Installation Process

The installation process for modified bitumen roofing systems typically involves five layers:

  • Insulation. Used to provide thermal resistance or R-value for temperature stability of the roof system. Commonly installed via mechanical attachment or foam adhesive.
  • Modified base sheets or plies. Features APP or SBS modifiers, as needed.
  • Modified bitumen membranes. These factory-fabricated sheet membranes are comprised of fiberglass or polyester-reinforced co-polymers.
  • Adhesive. A waterproofing material featuring a bonding agent is applied using either hot or cold methods.
  • Surfacing. Offers weathering resistance as well as UV protection when using a sheet with white granules.

Knickerbocker Roofing: Solutions You Can Rely On

For a flat or low-sloped roof, modified bitumen roofing provides reliable leak, UV, and heat resistance while being environmentally friendly and cost-effective. Knickerbocker Roofing has been a trusted source of industrial, commercial, and institutional roofing solutions for over 130 years. Our award-winning team consistently exceeds workmanship and service expectations. Learn more by getting in touch with our team today, or request a quote to get started on your next roofing project.