Although not usually visible to passersby, flat roofs are an important part of any building’s performance. In Texas, these roofs take a beating. Wind, hail, and sunshine (ultraviolet rays) combine to wear out ordinary roof systems. They can take years off a roof’s life, so it’s not surprising that many of Texas’ office buildings need new roofs every year.
Most flat roofs have a life-cycle of 10, 15, or 20 years; but, unfortunately, many do not last that long and require premature replacement. The right roofing system, however, with proper application and long-term care, can extend that life-cycle.
Engineers and architects understand how critical it is to keep structures watertight, so when an office building is due for rehabilitation, they look for the type of roofing system that will last.
Renovation or re-roofing of these buildings involves special challenges. In new construction, designers can plan for the variables in the project; but in renovations, the variables are set. Weight, slope of the roof, structural limitations, previous design changes, building occupancy codes, and other criteria can dictate what must be done to re-roof the building and meet the required design limitations.
In Texas - where renovation and re-roofing occurs regularly - many architects, building engineers, and contractors are looking to the versatility and reliability of self-adhesive roofing membranes for their building renovations.
Leon Cobb, president of ARCO Southwest Roofing Systems Inc., a roofing company in Parker, TX, that has roofed several office buildings in the Dallas area, uses self-adhered roofing membranes for many of his roof renovation projects. “They’re safer. When you use hot kettle systems, you limit the application and increase the chance of injury. We also use a self-adhered system to avoid the hazards of smell and noise,” confirms Cobb, a veteran of the roofing industry for more than 30 years. “Many roof renovations typically don’t allow a product that permits harmful fumes and unwanted odors because there are tenants in the building.”
Rand McReynolds, regional manager for Fernley, NV-based Polyglass USA Inc., a leading supplier of self-adhesive roofing technologies, knows that many architects agree with Cobb. “Self-adhesive roofing membranes are providing a strong alternative to the traditional hot mop or torch applications. The self adhesives are clean, safer, strong, and easy to install. Roofing contractors have found that self-adhered membranes meet their needs and allow them to meet the demands of architects, engineers, and building owners.” Polyglass, the acknowledged leader in self-adhesive roofing technologies, continues to provide self-adhesive, environmentally strong solutions for re-roofing applications. Its products are used regularly by Cobb.
Recently, ARCO re-roofed two brick office buildings in Addison, TX, (just outside of Dallas) called Bent Tree Towers 1 and 2. The buildings’ flat roofs needed to be replaced due to hail damage. Eight stories high with no parapet walls, the towers were also in close proximity to surrounding buildings, making safety an even bigger issue than normal. Because the buildings are located adjacent to the North Dallas tollway, code restrictions were very specific about not allowing hot kettle systems. “Even if we wanted to use a hot kettle system, we would have had to use long pumps to transport the hot tar from the ground to the roof,” commented Cobb. “It was out of the question.”
The original roof on both towers consisted of a three-ply roof with tar and gravel overlaid with a 10-year-old built-up system. ARCO’s first job was removing all of the old roofing. “When we removed the original roof, about 150,000 pounds [were] taken off of each building. That’s a lot of weight, and it creates unnecessary stress for a building,” said Eric Wilder, chief engineer for Sabre Realty, the owner of Bent Tree Towers.
The transition from the old ballasted and built-up roofing systems to a self-adhesive modified bitumen roofing system was a sigh of relief for the building and all of its tenants. “By replacing the old system with a self-adhered system, we took a huge amount of weight off of the roof. The existing system had put excessive strain on both building structures,” adds Wilder.
With the old roofing removed, the roof decks of the towers were visible and they were by no means identical. Tower 1 had a steel pan deck, while Tower 2 had a concrete deck. In the new installation, the ribbed metal on Tower 1 was fastened to joists in the roof, insulation was installed, and then the Polyglass Elastoflex® SA base sheet was installed over the insulation. An Elastoflex SA Cap Sheet was used to finish off the installation.
“It is pliable, particularly at low temperature conditions, and very versatile,” said McReynolds. “We have found that the Elastoflex SA membrane group is an extremely user-friendly membrane for roofing contractors and, in turn, building owners and architects.”
Manufactured using patented ADESO® technology, the Elastoflex SA membranes consist of a “true” SBS compound on the top layer of the sheets. This provides the strength, weathering resistance, and waterproofing performance to keep the building in the dry. The bottom layer utilizes an aggressive, unique self-adhesive compound which insures that the roof system adheres to the substrate and stays in place against wind and minor system stress. Guaranteed to provide a long-lasting and durable roof, the Elastoflex SA self-adhesive membrane with ADESO technology uses the latest in asphalt adhesive advances, as well as proven long-term membrane waterproofing compounds. The technology is further enhanced with the FastLap seaming system. This technology provides a self-adhering, factory-applied lap system at the end of each roll that improves the speed of application and a quick and clean positive lap to insure superior bonding and strength. Membranes utilizing ADESO technology are easy to use, safe, environmentally friendly, odorless, and insurance friendly.
A unique feature on Tower 2 was an old running track on the top of the building. “It was used in the 1980s but has since been abandoned due to safety issues,” noted Wilder. The self-adhesive roofing system easily molded to the oval-shaped jogging track. Raised about 4 inches from the roof level, the covered running track was overlaid with the new roofing SA membranes, smoothly transitioning the closed track with the field of the roof.
For the building owner, getting two buildings with long-lasting, minimal-maintenance roofs seems quite simple. “The process of roofing the buildings was very easy,” said Wilder. “The building was in operation during the re-roof, and there was little to no work interruption. There was no smell [or] mess, and very little noise.”
Though both office buildings had different features and unique elements, both shared a common need for a roof that is safe, efficient, and durable. Self-adhered systems are suitable virtually types of office buildings. Whether they are in close urban settings or sprawling suburban locations, low-, mid-, or high-rise, architects can incorporate self-adhered flat roof systems to promote a safe, durable, environmentally efficient, and long-lasting application.
Deanna Fryer is a freelance writer for the construction industry.