Modified bitumen roofing is a popular choice for flat and low-slope roofs in commercial and residential settings. It combines durability, flexibility, and compatibility with other materials, making it an appealing option for many property owners. However, like any roofing material, it has its share of pros and cons. Here’s an overview of the main advantages and disadvantages of modified bitumen roofing:
Modified Bitumen Roofing Pros & Benefits
Pro 1: Modified Bitumen Roofing has Multiple Layers and Adequate Thickness
Modified bitumen roofing systems typically consist of at least two layers, also known as plies, which provide superior durability and thickness. A standard 2-ply modified bitumen system with a granulated cap sheet is often over 240 MILS thick, significantly outperforming single-ply thermoplastic membranes, which are typically only 60 MILS thick. This inherent thickness makes modified bitumen a trusted option for structures where membrane thickness is crucial.
Pro 2: Modified Bitumen Roofing is Suitable for High Traffic Areas
Flat roofs often endure significant foot traffic, whether from maintenance personnel or improper use as a patio. Modified bitumen roofing systems are designed to handle such conditions better than many alternatives. With a granulated cap sheet and a robust multi-layer design, modified bitumen roofs resist wear and tear caused by foot traffic, making them ideal for roofs subjected to frequent activity.
Pro 3: Modified Bitumen Roofing is Compatible with Asphalt-Based Roofing Systems
Modified bitumen roofing systems are asphalt-based, making them compatible with readily available repair products like wet patch or roofing cement. This compatibility simplifies emergency repairs, even for personnel unfamiliar with specialized roofing materials. Unlike single-ply systems, which often require specific repair products, modified bitumen offers versatility and convenience in maintenance situations.
Pro 4: Modified Bitumen Roofing is Fire and Wind Damage Resistant
The asphalt content in modified bitumen roofing contributes to its excellent fire resistance, reducing the risk of flame spread. Additionally, its durable multi-layer construction offers superior protection against wind uplift and potential roof deck damage. These characteristics make modified bitumen a reliable choice for regions prone to extreme weather conditions, ensuring better safety and longevity.
Pro 5: Modified Bitumen Roofing is Flexible in Nature
Flexibility is another standout feature of modified bitumen roofing. Comprising asphalt and reinforced fibers, the material adapts well to temperature fluctuations and resists impact damage. Its flexibility and durability make it suitable for both commercial and residential applications, particularly for structures in climates with extreme weather changes.
Modified Bitumen Roofing Cons
Con 1: Modified Bitumen Roofs Have a Shorter Lifespan
One downside to modified bitumen roofing is its relatively short lifespan. While 15 to 20 years is a decent duration for a commercial roof, it pales compared to other roofing options like EPDM, which can last much longer. Property owners seeking a long-term solution may need to weigh this limitation carefully.
Con 2: Modified Bitumen Roofing is Vulnerable to Standing Water
Flat roofs with inadequate drainage systems are problematic for modified bitumen roofing. Puddles or standing water from rainstorms can degrade the roofing material over time, leading to leaks and premature aging. Proper drainage is essential to mitigate this issue, as water ideally should clear within 48 hours under typical conditions.
Con 3: Modified Bitumen Roofing Absorbs More Heat
Dark-colored modified bitumen roofs, such as those in black or minimally reflective shades, tend to absorb heat, raising indoor temperatures. This characteristic can result in higher cooling costs in warmer climates. While lighter or reflective color options are available, they may still fall short of the reflectivity of white thermoplastic materials.
Are Modified Bitumen Roofs The Best Choice For Flat Roofs?
Modified bitumen roofing systems offer many advantages, including durability, flexibility, and compatibility with asphalt-based repair materials. However, they also come with drawbacks, such as a shorter lifespan and vulnerability to standing water. Whether modified bitumen is the best choice depends on your specific needs, climate, and roof structure. Consulting with a roofing professional can help you determine if this roofing system is the right fit for your property.
