Even as single-ply commercial roofing systems continue to advance, asphalt roofs often remain the best choice in terms of durability and longevity for most types of buildings. Consisting of two or more waterproofing layers, the tried and true asphalt-based roofing system continues to provide building owners with a durable solution for long-term protection against water intrusion.
This article will discuss the evolution of asphaltic roofing systems while elaborating on their various benefits, types, and installation methods.
History and Evolution of Asphaltic Roofing
Asphalt roofing systems have been utilized for more than a century. The first application of asphalt roofs consisted of four to six layers of fiberglass rolls applied with around 500 degree hot asphalt. The asphalt would be spread over the roof surface with a yarn mop (think Shawshank Redemption when Andy and his fellow inmates are spreading “tar” on the roof.) This method was known as Built-Up Roofing, or BUR because roofing contractors could add ply sheets and asphalt until the roof reached its desired thickness.
Asphalt roofing system technology evolved in the 1960s, and the modified bitumen roofing system was born.
For context, it is important to note that bitumen is another word for asphalt. Manufacturers determined that altering the asphalt compounds would increase the effectiveness of traditional BUR systems and experimented with adding revolutionary materials of the time.
This experimentation spawned two modified bitumen roofing solutions that are still widely used today.
The SBS (Styrene Butadiene Styrene) system introduced synthetic rubber to the bitumen compound. This modification provided commercial roofing contractors with installation flexibility without sacrificing the benefits of BUR. Soon after, manufacturers developed the APP (Atactic Polypropylene) roofing system utilizing plastic-infused bitumen to achieve additional environmental protection.
Benefits of Asphaltic Roofing
There are many reasons why asphalt roofing systems have maintained their popularity for over 100 years. They offer reliability and durability while providing numerous installation options for commercial roofing contractors and building owners.
Contractors can build up asphaltic roofing systems to essentially any desired thickness. The design, materials, and multiple layers make the roof highly effective against water intrusion and other harm that the elements can cause.
Asphaltic roofing systems are also unsurpassed in terms of durability. This provides excellent value for buildings where a high degree of foot traffic on the roof is expected. For example, a common occurrence like a vendor dropping a tool while performing an equipment repair on a polymer roof will likely create a hole that allows water to penetrate. An asphaltic system would be largely unaffected.
The variety of asphaltic roofing systems available and the multiple installation options provide commercial roofing contractors and building owners assurance that they can receive the reliability and durability benefits of asphalt roofs in virtually any application, including new construction or replacement roofing.
Finally, there is also an aesthetic benefit to asphaltic roofing systems. As a two-phase solution, a commercial roofing contractor can complete phase I to seal the structure and allow all work to commence. Once construction is finished inside and out, including all equipment housed on the roof, the commercial roofing contractor can return and complete the second phase by placing a pristine cap sheet that seals the roof and gives a clean appearance upon completion.
Types of Asphaltic Systems
Built-Up Roofing (BUR)
The traditional asphaltic roofing system is known as Built-Up Roofing, abbreviated to BUR. Installation of this system involves liquefying bricks of asphalt to 500 degrees and pumping it up to the roof. The asphalt is then applied with mops over a base sheet and ply sheets until the roof reaches the desired thickness. An applied cap sheet or evenly spread gravel layer finishes the installation.
BUR has fallen out of favor over the years as the high heat required for application creates a safety risk, and modified bitumen systems have simplified overall installation.
Styrene Butadiene Styrene (SBS)
One variant of the BUR roofing system is the Styrene Butadiene Styrene (SBS) system. In SBS, the bitumen is modified with a synthetic rubber that enables increased elongation. SBS eliminates the safety risks associated with BUR by providing additional application options to commercial roofing contractors, including torching, cold-adhesive applied, or even self-adhered.
In SBS systems, crews install a base sheet over insulation or cover board, apply the modified bitumen base ply, and then finish the system with a cap sheet that can be granular or smooth. Recent advancements have also allowed the granules which are impregnated into the capsheet, to be reflective white, thus qualifying for the Energy Star reflectivity rating.
Atactic Polypropylene (APP)
Another BUR variant is the Atactic Polypropylene (APP) roofing system. In this method, bitumen modified with plastic provides additional durability and maximizes protection against UV rays and weather events.
APP systems can be applied in hot asphalt, cold adhesive, or via torching. Contractors usually prefer to torch APP membranes, because the molten bitumen is very heavy and easy to work. APP systems can also be manufactured with reflective granules to provide Energy Star ratings.
Installation Methods
There are multiple methods to install asphaltic roofing depending on the system selected and the architect’s specifications.
The oldest method is hot-mopping. Used to apply traditional BUR systems, commercial roofing contractors melt blocks of asphalt in a large kettle, then use mops to apply the asphalt evenly on the roof.
Another option is heat-welding or torch-applied. In this method, the roofing membrane comes pre-manufactured with asphalt on the underside of the membrane. The installer melts this asphalt with a torch during installation, and the heated asphalt adheres the sheet to the roofing substrate below.
An opposite possibility is a cold-applied installation. In this method, the installer applies a liquid adhesive with a notched squeegee or applicator gun onto the substrate and then attaches the roofing membrane.
Some manufacturers also offer a self-adhered asphaltic roofing system option. As it sounds, this method involves a roofing sheet with an integrated adhesive. Installers simply peel a film backing and attach the membrane.
Each method has benefits and drawbacks. It is crucial to partner with an established commercial roofing contractor experienced in all types of commercial roofing installation.
Are you considering an asphaltic roofing system for your building? We want to talk to you!
Register Roofing has served building owners, property managers, architects, and general contractors throughout the Southeast for over 40 years. Our experienced team can consult with you on your commercial roofing project whether you need a repair, a replacement, or a brand-new roof.