A Handy Guide to Commercial Flat Roofing Options – Part 2: Modified Bitumen Roofing

There is no denying the fact that flat roofs dominate the commercial roofing industry. Aside from addressing roofing needs, flat roofs also open up space on top of a building so a business can use the space to expand its operations. Interested in a vegetated roof? Flat roofing options may also be installed under green roofs as well, allowing you to do your bit for the environment while taking care of your roofing needs. Flat roofs do offer a number of advantages, as a modified bitumen roof would prove.

What It Is

Polymer-modified bitumen, more popularly called modified bitumen, was first developed in the 1960s. It later on found its way across the Atlantic and into the United States where it gained traction in the 1970s. It is said to be a combination of single-ply roofing and built-up roofing in that it harnesses the installation ease offered by former and the durability of the latter. How? Hot polymer-modified bitumen is poured over reinforcing fabrics, turning into a multi-ply roofing system with the durability of built-up roofing. But as it comes in a roll, it is easy to handle like single-ply roofing.

There are two kinds of modified bitumen membranes:

  • SBS (Styrene-Butadien-Styrene) Polymer-Modified
    • elastomeric extenders
    • more flexible than APP at cold temperatures
    • more complicated to produce than APP though, relying on bitumen-elastomer compatibility
  • APP (Atactic Polypropylene) Polymer-Modified
    • thermoplastic extenders
    • heat-welded
    • requires higher temperatures for torching process

What Makes It a Great Choice?

  • It’s durable like multi-ply systems but easy to install like single-ply roofing.
  • It can withstand a range of weather conditions, flexibly expanding and contracting with the temperature to adapt to the elements.
  • It can help reduce energy costs, stabilizing indoor temperature by preventing excessive heat from being absorbed through the roof.

A Quick Note

It’s easy to confuse modified bitumen and EPDM roofs because they are both colloquially referred to as rubber roofs. To avoid mix-ups, best to call roofs by their actual name when talking to a roofing contractor.

Modified bitumen is durable like built-up roofing. But what is BUR? What can it offer you? Read on to learn more about this flat roofing option.