AT A GLANCE

• Cost: $$$
• Lifespan: 20+ years
• Color Options: White, black, brown, gray, green, red
• Composition: Asphalt with Atatic Polypropylene (APP) modifiers or Styrene Butadine Styrene (SBS) modifiers.
• Advantages: Proven durability. High UV, ozone, and chemical resistant. White membrane is Energy Star Certified.
• Disadvantages: Expensive to maintain. Difficult to diagnose and repair leaks. Does not perform well with standing water.

Modified Bitumen roofing is the latest iteration of Built-Up Roofing systems that have been used for centuries. It is a roof system comprised of three layers — a waterproofing layer, a reinforcing layer, and a surfacing layer to protect the others. Modified Bitumen roofing systems involve adding synthetic polymers added to asphalt to provide increased elasticity and resistance to cold temperatures.

INSTALLING MODIFIED BITUMEN ROOFING

Modified Bitumen roof systems can be installed by torch application, hot mopping, or cold process adhesives. Improvements in adhesives and manufacturing processes have made the cold process method preferable due to the elimination of fire risks and hazardous fumes.

Modified Bitumen include a combination of a base sheet, ply sheets, and cap sheet. The addition of one of more ply sheets increases the life expectancy and warranty of a Modified Bitumen roof system. The cap sheet is typically mineral or gravel surfaced which allows for many color options, including “cool roof” coatings that can maximize energy efficiency and achieve energy star ratings.

As with most roof systems, there are many factors to consider when installing a Modified Bitumen roof system, including desired lifespan, wind uplift ratings, and compatibility with chemicals.