There are many signs that it’s time for a new roof, from rising energy bills to interior water damage. You may not realize that an outdated roof may not be up to code, meaning it’s more than just a cosmetic issue.
If you have a flat or low-slope roof, you should consider polymer-modified bitumen roofing when looking for replacements. Popular since the 1960s, modified bitumen takes less time and money to install than many of your alternatives.
Ready to learn more about modified bitumen roofing? Read on for our complete guide.
What Is Modified Bitumen Roofing?
Modified bitumen membranes have been a popular commercial roofing choice in the US since the 1970s. Modified bitumen is created by adding polymerized rubber to asphalt. Modified bitumen is an evolution of built-up roofing, which was once the go-to roofing method for all low-slope and flat roofs.
While built-up roofing is still viable, modified bitumen roofing aligns more with the latest roofing trends. When installed by a licensed roofer, it provides longevity, efficiency, and weather-resistance that built-up roofing can’t beat.
Types of Modified Bitumen Roofing
There are two main types of modified bitumen roofing membranes. These options have slightly different properties and require different installation methods.
SBS Modified Bitumen
SBS polymer-modified bitumen roofing membranes impart a rubber-like quality in the asphalt. This provides a level of flexibility that can withstand significant temperature fluctuations. The SBS modified polymer also ranks high in water resistance.
Installing SBS-modified bitumen involves either hot mopping or cold adhesives. Some of these membranes have a self-adhesive (sticky) backside, but we don’t recommend using this method to install or repair your roof.
APP Modified Bitumen
APP polymer-modified bitumen roofing membranes impart a plastic-like quality to the asphalt. This quality increases UV resistance and helps remove natural water to prevent pooling and damage.
Installing APP-modified bitumen involves heat welding or torch applications. Proper safety gear is a must when using these methods. Off-gassing can produce fumes that aren’t safe to breathe (but will dissipate quickly).
Pros of Installing Modified Bitumen
If you’re not a roofing expert, the chemical makeup and installation processes may not tell you what you need to know. Here are some of the cut-and-dry benefits of installing modified bitumen on your flat or low-slope roof.
Durability
Membrane roofs provide tremendous tensile strength. Their flexibility makes them durable enough to withstand storm damage and debris, an increasingly important quality in the Southeast. Maintenance and upkeep are important, but you may spend less on climate-related repairs.
Fire Resistance
Modified bitumen membranes offer superior fire resistance after installation. Some membranes have Class A fire ratings, which is the highest rating roofing materials can receive. This can improve the overall safety of your property, especially older properties with more potential fire hazards (e.g., outdated electrical systems).
Energy Efficiency
Roofs are a primary culprit when it comes to commercial property energy loss. Not all modified bitumen membranes provide the same energy efficiency, but many provide superior protection. Tight seals, a solid insulation barrier, and UV resistance (higher in APP) can prevent energy loss and heat gain.
Waterproofing
Water damage is a major concern with all flat and low-slope roofs. You may still have some pooling issues when using certain kinds of bitumen roofing membranes. However, multi-ply installation can provide long-lasting waterproofing to prevent interior water damage.
Cons of Installing Modified Bitumen
There are many great reasons to choose a modified bitumen roof. However, it’s not always the best choice for everyone. Here are a few of the issues that may arise with one.
Potential Heat Absorption
As mentioned earlier, APP-modified bitumen provides UV resistance while SBS-modified bitumen doesn’t. It’s also important to remember that dark asphalt-based materials can absorb heat. Dark-modified bitumen may contribute to interior heat gain without UV-resistant properties or proper insulation.
Poor Foot Traffic Resistance
Modified bitumen offers some durability, but its maximum lifespan tends to hover around 20 years. Regular wear and tear can speed that process up, and there are better choices for areas with high foot traffic. If your roof is functional and open to employees or tenants, you may want to consider alternatives like built-up roofing.
Installation Odors
Along with potential off-gassing, some installation methods can produce strong odors. You may want to move employees during installation. Fortunately, installation takes little time.
Typical Components in a Modified Bitumen Roof
Modified bitumen roofs resemble built-up roofing in that they consist of multiple layers. However, these layers are lighter, putting less strain on your property’s structure. Let’s take a look at what layers to expect.
Insulation and Vapor Barrier
All modified bitumen roofs start with a layer of insulation. This provides thermal resistance and indoor temperature control. Depending on your roofing system, this may be followed by a vapor barrier.
Overlay
If you’re using APP with a torch application, you’ll need an overlay board. This requires professional installation for a proper seal and protection. You may not need this layer if you’re using SBS-modified bitumen.
Modified Bitumen
Next comes the base layer of modified bitumen. This layer is almost always torch applied or hot mopped. Then, at least one more modified bitumen layer is applied to create more durability and weatherproofing.
Contact Us for Commercial Roofing Services
Are you ready for a commercial roofing upgrade? Modified bitumen roofing may be the right choice if you have a flat or low-slope roof. This is an affordable choice with plenty of benefits and fast installation.Benton Roofing is proud to provide full commercial roofing services across the southeast. With over 40 years of experience, we’ve seen the devastating impact when roofers cut corners or don’t use climate-specific methods. Learn more about polymer-modified bitumen and request a quote for the best prices and quality.