Comparing Flat Roofing Systems: SBS, Tar and Gravel, and EPDM
- Lilian Jourieh
- Oct 3
- 3 min read
Most commercial buildings have flat roofing, and the three most popular systems are: SBS (Styrene-Butadiene-Styrene) modified bitumen, tar and gravel, and EPDM rubber. There are best use cases and trade-offs for each system. Understanding how they are different helps the building owner choose the right systems for a buildings’ need, budget, and climate.
SBS Modified Bitumen
SBS (Styrene-Butadiene-Styrene) modified bitumen is an improved version of older asphalt-based roofing. Manufacturers developed a roofing material that is waterproof and flexible in both hot and cold weather by combining asphalt with rubber and plastic polymers.
SBS roofs can be installed using adhesives or heat (torch-on), which allows them to be used on a variety of job sites. Layers of modified bitumen are typically separated by a reinforcing sheet made of fiberglass or polyester, which gives the roof extra durability.
This type of roofing is renowned for its resilience to punctures and capacity to withstand building movement without breaking. While smooth-surfaced SBS systems offer a variety of finishing options, some systems have granular surfaces for fire and UV protection. If properly maintained, SBS systems often last 20 to 25 years, because damaged areas can be repaired without replacing the entire roof, making maintenance rather simple.
Tar and Gravel (Built-Up Roofing)
Built-up roofing (BUR), also known as tar and gravel roofs, has been in use for more than a century. They are made by piling bitumen (or tar) and reinforcing felt in alternating layers, then covering them with gravel.
In addition, to adding weight, the gravel protects against UV rays, is fire resistant, decreases temperature fluctuations, and increases durability against foot traffic and wind. If properly maintained, these roofs can endure for at least 30 years because they have several waterproofing layers.
The downside is that not all buildings can handle tar and gravel systems because of their weight. Additionally, they need to be maintained on a regular basis to maintain adequate drainage and an even distribution of gravel.
EPDM Rubber Roofing
EPDM (Ethylene Propylene Diene Monomer) is a type of synthetic rubber membrane that changed the flat roofing industry when it was first introduced. It is popular due to being lightweight, flexible, and extremely resistant to weathering from heat, UV, and ozone.
EPDM can be fully glued down, mechanically fastened, or weighted with ballasts. It also comes in big sheets, which reduces the number of seams and makes installation faster. It holds up in a wide range of temperatures from extremely cold to very hot and usually lasts 30+ years.
The white version of EPDM is available for energy savings in hot climates, while the black version absorbs heat and is ideal for cold climates. Repairs are generally easy and involve the use of seam tapes or adhesives.
Which One to Choose?
The best choice depends on factors like climate, budget, and building structure.
· SBS is adaptable and can be repaired, which makes it an excellent all-around choice.
· Tar and Gravel offer excellent durability and thermal benefits but requires a stronger structure.
· EPDM works well in extreme weather and is easy to maintain.
Initial cost isn’t the only factor; maintenance, energy efficiency, and lifespan also contribute to long-term value.
Final Thoughts
SBS, tar and gravel, and EPDM all offer reliable protection, but the best roof depends on a property’s specific needs. For expert advice and installation, MTM Roofing provides all three systems and helps property owners choose the one that fits their building and budget.
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