There are 3 main types of flat-roofing systems: built-up roof (BUR), modified bitumen and single-ply. Each system is designed to waterproof the roof and protect it from sun, rain, snow and more. This prevent leaks, mold and rot—all of which can weaken the roofing structure and cause costly damage.
To help you evaluate your options, we’ve detailed all 3 roofing systems below.
Built-Up Roof (BUR)
Around for more than a century, BURs were the most common flat-roofing system until the advent of single ply. BURs use multiple layers of tar and gravel to create a watertight seal over the roof, which protect bottom layers from damage.