Choosing a commercial roofing system is a big decision for property owners and facility managers. Two of the most common systems are Built-Up Roofing (BUR) and TPO (Thermoplastic Polyolefin) . Each has unique strengths, applications, and considerations. Let’s compare the differences so you can make an informed choice.
Built-Up Roofing (often called “tar and gravel roofs”) has been used in the U.S. for over 100 years, making it one of the oldest and most proven commercial roofing systems.
What it is: BUR consists of multiple layers of asphalt (bitumen) alternated with reinforcing plies, finished with a gravel or mineral cap sheet. A common hybrid variation includes a modified bitumen cap sheet for additional flexibility and performance.
Withstands harsh weather when installed and maintained properly
Heavier than single-ply membranes, requiring a strong deck
More complex installation with hot asphalt or adhesives
Standing water can cause soft spots, blistering, or surface undulations if drainage is poor
Expected lifespan: 20–30 years with proper installation and maintenance
TPO is the fastest-growing single-ply membrane system in the U.S., introduced in the late 1990s.
What it is: A lightweight, flexible membrane composed of polypropylene and ethylene-propylene rubber, reinforced with polyester scrim. TPO sheets are mechanically attached or fully adhered, with seams heat-welded for a watertight finish.
