While the Seattle area is known for rainfall, last fall had even the web-footed Seattle natives complaining as a record 91 days of measurable precipitation fell between November 1, 1998 and March 1, 1999. According to Ron Haight, project manager, the Johns Manville UltraGard® SR-60 and SR-80 PVC membrane allowed for some very creative installation techniques, which couldn't have been utilized with other roofing materials.

 

"Because of UltraGard, we were able to adapt very quickly to the constantly changing weather conditions, and actually accelerate the installation," Haight said. "We started off three months behind schedule and you can bet everyone on the project was surprised when we caught up to, and pushed, the trades installing the roof decking."

 

The very complicated project is broken into two groups of roof decks--the councourse level, which is comprised primarily of smaller buildings to accommodate the services and concession vendors, and three large movable roof panels. Mechnical fastening was used to secure the roofing membrane and underlayment materials through the steel roof decking at all areas.

 

The concourse level roof used a ¼" per foot tapered ISO 1™ insulation system to create the necessary slope to drain. The movable panel sections have adequate slope in the structure already and are comprised of acoustical fiber glass sound control strips placed in the bottom of the decking with 5/8" underlayment providing the substrate for the UltraGard PVC membrane.

 

 The roof structure covering the playing surface and seating consists of three separate moveable panels. Panels one and three are essentially identical and tuck under panel two when fully retracted (field exposed). These panels closely resemble typical arched bridge/truss construction, which results in a barrel shaped roof deck design. Because panels one and three reside beneath panel two, most of the structure of panel two is above the roof decking resulting in roughly 300 steel beam penetrations. Each beam penetration protrudes at differing angles through the roof deck, further complicating flashing details thereby requiring more thinking "out of the box." The problem was easily solved, however, when the design team from Haight used Ultra Gard PVC clad-metal to form barrel-like enclosures around the base of the beam. The top edge of the beam flashings tucks under a steel collar which is welded to the beam and the bottom edge is fastened into the steel decking. The enclosures are then flashed into the roof system using UltraGard PVC membrane welded directly to the enclosure. According to Haight, "It makes for an extremely secure and clean looking detail."

 

 The roof decks run from low slope to vertical with the most severe areas, commonly known as the "eyebrows" hovering more than 200 feet above ground. Access to these areas was limited, requiring the roofing team to be suspended from safety harnesses linked to lifelines attached to the structure. This greatly reduced the ability of the roofers to handle materials and tools. Fortunately, the UltraGard PVC provided for easy manageability in the field, a huge consideration given the extreme conditions encountered during the installation.

 

"Haight Roofing has been in the roofing business since 1919. We've completed numerous unique projects during that time under just about any condition you could imagine," Haight said. "Without the inherent ease of use characterstics of the UltraGard PVC membrane we just may have finally met our match with this job. We were very impressed."

 

Another unique aspect of the roofing design was the custom color which was selected by the architects, NBBJ of Seattle. According to architect Knut Hansen, the "Mariner Gray" was selected to blend in with the color scheme utilized on the building. "We liked the color relative to other materials on the project," Hansen said. NBBJ also preferred the UltraGard PVC membrane based on the strength of its welded seam.

 

The general contractor on the job was Hunt-Kewit Joint Venture and the Johns Manville Representative was Eric Weller. The stadium is owned by Washington State Major League Baseball Stadium Public Facilities District.

 

This is the fourth stadium project sporting a Johns Manville UltraGard PVC roofing system. Bank One Ballpark in Phoenix, Lexington Center in Kentucky and the Jerome Schottenstein Center Value City Arena at Ohio State University also have UltraGard single ply roofing systems. According to Michael Johannes, Director of Marketing for Johns Manville, "UltraGard PVC is a great product for arenas. It comes in custom colors and is easy to apply."

 

Johns Manville is a leading manufacturer and marketer of premium-quality building products. The 141-year-old Denver-based company had sales of $1.8 billion in 1998. Johns Manville employs approximately 9,200 people and operates 54 manufacturing facilities in North America, Europe and China. Additional information can be found at www.jm.com