In their search for roofing solutions, designers, contractors, and consumers search for the ultimate answer to their roofing needs. With a plethora of manufacturers offering various types of roofing materials, the impression is that there appears to be a roof for every building type and design. However, not all roof types and/or systems work well for every construction design, especially in the case of low-sloped roofs.
Asphalt-based roofing materials and systems have a very long history of effectiveness in protecting buildings for more than 200 years. Over the last 50 years, significant advancements in chemistry have transformed traditional built-up roofing (BUR) systems into something new and exciting. The integration of polymers has enhanced the base asphalt with flexibility and improved resistance to challenging weather conditions.
Today, the most popular asphalt-based systems are based on Atactic-Polypropylene (APP) and Styrene-Butadiene-Styrene (SBS) polymer-modified asphalt chemistry, known as modified built-up roofing systems (MBUR). These systems offer numerous benefits that extend beyond their initial conception many decades ago.
The Evolution of Asphalt-Based Systems
Asphalt-based roofing systems have stood the test of time. The traditional Built-Up Roof (BUR) is essentially constructed on the rooftop by applying various coated membranes or saturated felts. These layers require the use of a fluid “mopping-grade” asphalt to penetrate and bond them together resulting in a waterproof assembly. The base assembly of these types of systems needs protection from long-term sunlight or UV exposure. In the early years, natural gravel or aluminized coatings were used for this purpose. As options expanded, cap sheet membranes with embedded ceramic colorized granules became the preferred choice.
With the invention of polymer-modified asphalt roof membranes, the vulnerability associated with roof-top assembly changed the dynamics. The introduction of polymer-modified asphalt membranes now offered materials, inherently impermeable to water. The use of these products to form an MBUR system only requires proper bonding and seaming to create a robust, waterproof roofing system. This simplification of the roofing process has ushered in a new era for asphalt-based roofing systems.
Tailoring Your Roof to Your Needs
When selecting a roofing material or design, it must align with your specific project requirements. Modified asphalt chemistry is ideally suited for a wide range of low-slope roofs and serves as an excellent underlayment for all steep-sloped roof coverings. While minimum building codes allow the use of felt underlayment that may not perform for the climate conditions or last anywhere near the lifespan of the roof covering, modified bitumen roofing, whether self-adhesive or mechanically attached, offers superior performance and longevity, ensuring the durability of your steep-roof covering.
Exploring Polymer-Modified Bitumen Membranes
Polymer-modified bituminous asphalt roof membranes are readily available with polymers possessing either APP (plastic-like) or SBS (rubber-like) characteristics. These characteristics offer unique advantages tailored to different climate zones and application procedures.
Polymer Modified Bitumen membrane designs are installed in one of the following four common ways:
- Heat-Fused (Torch-Down)
- Self-Adhered (Peel and Stick)
- Cold-Applied (solvent-based asphalt adhesives)
- Hot-Mopped (oxidized mopping asphalt or SEBS polymer-modified mopping asphalt)
The Benefits of MBUR Systems
So, why should you consider using MBUR systems over other roofing options? Let’s explore some of the most compelling advantages:
Durability
- MBUR materials with factory-applied surface granules perform in conditions of roof-top traffic.
- MBUR materials protect the surface from the damaging effects of direct sun exposure.
- MBUR materials excel in severe weather conditions, such as hail, often meeting the highest impact ratings of available roofing materials.
- MBUR materials use a polymer-modified asphalt compound that offers superior thermal stability, suitable for both the coldest and hottest climate regions.
- MBUR membranes exhibit superior puncture resistance, a common failure point for most non-asphaltic membrane types.
Longevity
- MBUR materials are built to last, and manufactured with reinforcing mats that offer strength and stability.
- Their chemistry enhances the asphalt’s performance, ensuring a long service life.
- Historically, modified bitumen layer on roof materials have proven to perform and remain in service for many decades.
Excellent Waterproofing Capabilities
- MBUR membranes are designed to be impermeable to liquid water and moisture vapor, even in the most severe weather environments.
Design Flexibility
- MBUR materials and systems are intentionally designed with flexibility to accommodate various building types and styles.
Why Choose MBUR Systems?
Modified bitumen roofing systems offer the best of both worlds. They allow multiple layers to be bonded together, offering the redundancy performance in traditional BUR systems, while embracing modern advancements in polymer chemistry to enhance the base asphalt characteristics.
Modified bitumen roof systems offer multiple product choices, suitable for basic and complex roof designs. With various application methods, MBUR is adaptable for those roofing in cold climates with heat-fused or hot-asphalt methods, or using cold-adhesives in more temperate conditions, and self-adhered options for projects sensitive to odors.
In contrast, some may choose a single-ply membrane, such as TPO, PVC, or EPDM, believing it’s a simpler system to specify and install. This choice is often driven by the perception that these systems are more cost-effective than MBUR systems. However, it’s essential to note that the use of inferior and often inadequate membrane thickness can result in repeated problems and even premature system failure. Thermoplastic materials oxidize and weather away over time, literally losing thickness over time, unlike MBUR which remains a constant thickness over time. The use of thinner membranes that are sacrificial is unlikely to provide decades of performance as MBUR materials have historically proven.
Compared to MBUR systems, these non-asphaltic membrane types tend to offer less flexibility for unique conditions, often requiring adaptation to suit less common roof designs. Their advantages are rarely related to superior performance but rather cost-effectiveness and ease of installation, sometimes even by unskilled workers.
Effortless Installation of MBUR Systems
The installation of MBUR systems is straightforward and not specialized, making it a routine process for skilled installers. A commonsense approach to pre-installation planning and deck preparation is important as with all systems. When beginning an MBUR installation, material handling and site organization are well-established practices. For those less familiar, manufacturer’s information and on-site training resources are readily available.
MBUR systems, whether they are heat-fused, self-adhered, bonded in cold-adhesives, or hot-asphalt, follow best practices recommended by the membrane manufacturer and are widely supported by industry groups such as the National Roofing Contractors Association (NRCA).
MBUR systems offer all the traditional roof-related details required for any project. Membrane and fluid-applied detail components are readily available for any project condition. Required primers, flashing cement, and mastics are all designed to work together for all project circumstances.
Ensuring Longevity with Minimal Maintenance
Maintaining your MBUR system is straightforward, with minimal maintenance requirements and no need for specialized products. If repairs become necessary, MBUR systems are user-friendly, requiring no specialized materials. Proper and minimal roof care can help ensure that your well-designed and installed MBUR system can perform for decades.
Enhancing Durability with Protective Coatings
MBUR systems are ideal for working with a wide variety of protective coatings, further extending the system’s lifespan. MBUR manufacturers offer a plethora of protective coatings to enhance performance and longevity. The use of protective coatings and periodic maintenance can offer opportunities for your MBUR system to be the last roof your structure may need. Some manufacturing sources in Europe even promote complete life cycles of up to 90 years. Shielding your MBUR from direct exposure to the elements can significantly extend its serviceable life cycle.
Frequently Asked Questions
What is the typical lifespan of modified bitumen roofing?
The life span and performance of an MBUR system, like all roofing systems is highly dependent on its proper design for the conditions and the quality of the installation. It is not uncommon for MBUR systems to be in service for at least 20 years with proper care and regular maintenance.
What is the process for repairing a modified bitumen roofing system?
Repairing modified bitumen roofing is generally straightforward. Most times a simple surface repair is all that is required. Should there be circumstances of moisture entering into the system, simply cutting out the damaged section of the membrane and repairing it with like materials is straightforward.
Can modified bitumen be installed in cold weather conditions?
Yes, modified bitumen can be installed in cold weather, but often can require some special consideration. To ensure successful installation in freezing temperatures, it’s essential to consider special storage and handling as well as the use of roofing products designed for cold-weather applications, such as Polyglass’ low-temperature polar cap and base membranes.
What is the difference between APP-modified bitumen roofing and SBS-modified bitumen roofing?
APP-modified bitumen roofing incorporates a plastic-like polymer (Atactic Polypropylene), providing durability and UV resistance, making it ideally suited for moderate climates. SBS-modified bitumen roofing includes a more flexible, rubber-like polymer (Styrene-Butadiene-Styrene), offering elasticity making it ideal for diverse weather conditions. APP materials are commonly applied with heat welding, however, self-adhesive type membranes are an increasing segment of this market. SBS roofing employs various methods, including heat welding, cold adhesives, or self-adhering membranes, allowing for flexibility in installation and suitability in colder climates. APP and SBS membrane types offer options with highly reflective surfacing for those projects requiring higher resistance to solar gain.
Polyglass®: Pioneering Polymer-Modified Solutions for Roofing Challenges
MBUR offers benefits that surpass those of any commercially available roof type. Whether you require decades of performance in cold weather, temperate climates, or the heat of the desert, polymer-modified membranes offer a solution. It’s crucial to select a well-suited roof system for your building’s needs, and equally important to choose a modified membrane manufacturer with expertise in the field of polymer-modified membranes.
Polyglass® is a leader in polymer-modified technologies, offering product choices such as commercial self-adhesive systems, meeting the growing demand for such systems. Whether you have a low-slope or steep-slope roof, Polyglass® has the answer to your roofing challenges and solutions.
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