PVC Roofing Installation Reaches for the Sky
by Fred Sitter, marketing director, Duro-Last Roofing, Inc.
From Architectural West Sep/Oct ’12
Every building should make a statement; about the building’s purpose, about the owner, and about the architect. Such was the case for one of the tallest structures in Sacramento, Calif., the Bank of the West Tower. The building has a unique, aesthetic design that can be seen throughout the city. Vivid blue and tan stripes separate each of the 25 floors, and the top of the building forms a striking two-story triangular glass penthouse.
Ed Kado, EM Kado Associates, Sacramento, Calif., was selected as the architect for this project. Kado states that the pinnacle of the structure, the triangular shaped two-story glass penthouse, was designed to be recognizable for miles when approaching the city. The sky-lighted glass penthouse was originally intended to serve as a restaurant, but was converted to office space as demand rose. Office space in the building is 70% leased.
Because several lower levels are visible from upper floors and neighboring buildings, the tower required a roofing system that would complement the attractive appearance of the building and would be easy to install. Selecting the right system for this project became a joint effort between architect Kado, roofing consultant Robert Cox, CEI Roofing California of Rancho Cordova (a Tecta America Company), and Robert Hemphill of Division 7 Reps, a Duro-Last® Roofing, Inc. sales representative agency. Ultimately, 33,000-sq.ft. of Duro-Last’s 50-mil single-ply roofing system were specified for the project.
Collectively, this team brought several decades of prestigious roofing experience to the table. Cox has consulted on roofing projects both in the United States and abroad, including guard towers that are part of the Great Wall of China. Among the high-profile projects CEI and Kado have worked on together is Sacramento’s distinctive, pyramid-shaped Ziggurat Building. CEI also roofed the nearby State Capitol and other Duro-Last projects in Sacramento and Walnut Creek, California.
The Bank of the West Tower presented unique challenges. “Obviously, most commercial roofing projects, including ours, are done on large, flat, horizontal surfaces,” said CEI operations manager, David McClain. “By contrast, the roof on this building consists of many small deck sections that are on nine separate levels on the façade.” The building’s multiple levels of structural concrete deck required a fully-adhered roof assembly to minimize installation labor and provide wind uplift security on a building with roof sections more than 300’ in the air. According to McClain, the fully-adhered Duro-Last system provided a very good solution.
The assembly included tapered polyiso insulation that was applied to the concrete deck areas. That was covered with SECUROCK® roof board, then the Duro-Last PVC roof membrane. On two of the nine roof deck levels, the Duro-Last membrane was overlaid with concrete pavers.
The order for the roof included pieces of tan membrane ranging in length from 60’ to 100’ that were used for both deck and parapet areas. These membrane sections were made to the specified sizes by Duro-Last and delivered to the jobsite along with the rest of the order, which helped CEI better manage on-site labor costs.
The project began in September of 2008 and was completed in April of 2009. According to McClain, the roof was installed in stages that corresponded with the overall construction schedule, and took about 15,000 man-hours to complete. The biggest challenge was the logistics of getting the roofing materials from the ground to the deck areas. CEI crews lifted the roofing system sections onto each roof area using a tower crane and then transported the remaining materials, such as adhesive and heat guns, via the building’s elevator. However, “because the Duro-Last PVC membrane is lightweight, our crews were able to maneuver the material on the various rooftop levels easily, even in the more confined areas,” he said.
Among the unique aspects of the job were approximately 600 penetrations through the deck and parapet roofing membrane sections to accommodate guardrails on the lower levels of the building. Customized round flashings to fit each of these penetrations were precision-fabricated in Duro-Last’s west coast manufacturing facility, which really helped speed up the installation time, according to McClain. “Normally, we would have needed to create each of those flashings on-site by hand with roofing material,” he said. “Because Duro-Last made all of those for us, we were able to reduce our installation time significantly. We just fit each custom-fabricated flashing around the guardrail bases and heat-welded them to the deck membrane. Each one took less than five minutes to install.”
More importantly, by taking away the need to make them by hand on the rooftop, the prefabricated flashings will help ensure a watertight seal for all those penetrations, virtually eliminating the opportunity for future leaks to develop at 600 locations around the building.
“We’ve been working successfully with PVC roofing membranes for more than 30 years,” said McClain. “Duro-Last’s material is very flexible and easy to weld. It helped improve our installation efficiency so that we could allocate labor to work on some of the more unique details of the project.” McClain continued, “Between our specially-designed flashings and the efficiencies we gained because we used Duro-Last, we estimate that we saved this customer about $1 million on construction costs.”
Those details consisted of nearly four linear miles of custom metal flashing that CEI designed and produced specifically for the Bank of the West Tower, including almost two miles of cornice flashing that was used to terminate parapet sections made from Duro-Last membrane. The perimeter edge metal for the facility was manufactured by Metal-Era, Inc. The architect selected 3,400 lineal feet Metal-Era’s Anchor-Tite Standard Fascia with a 30” long custom cornice shaped extender. To achieve the rich, classic appearance of stone masonry, a custom spatter coat stone-look finish was used that matched other stone used on the project. The distinctive extender, when combined with the stone-look finish, created a look that blended well with the overall design aesthetics of the building.
One-stop shopping was also an important feature in selecting Duro-Last for this project, according to McClain. “Duro-Last’s Grants Pass, Oregon, manufacturing facility shipped all the materials we used on the job. The deck and parapet sections, adhesive, custom membrane flashings, and many other components came directly from the manufacturer to the jobsite. This factor helped us control the logistics of this installation very effectively.”
Regardless of the building dimensions or the application method, the Duro-Last roofing system is ideal for any structure. “The Bank of the West Tower is a showpiece for the city of Sacramento and will be a prominent feature of the skyline for decades,” concluded David McClain. “We’re confident that our Duro-Last installation will maintain the dual high standards of aesthetics and functionality for this facility well into the future.”