Photo courtesy of Black Roofing Inc., Boulder, Colo.
Photo courtesy of Black Roofing Inc., Boulder, Colo.
Photo courtesy of Black Roofing Inc., Boulder, Colo.
Denver Art Museum, known for its permanent and temporary art collections, family-friendly environment and interactive activities encouraging art appreciation, also is recognized for its striking appearance. It comprises two architecturally bold buildings—the North Building, which opened in 1971, and the Frederic C. Hamilton Building, which opened in 2006—joined by an elevated walkway.
The North Building was designed by Italian architect Gio Ponti and Denver-based James Sudler Associates. The seven-story, 210,000-square-foot building was designed to move away from traditional, temple-style museum architecture. The building's exterior features more than 1 million reflective glass tiles and a castle-like facade.
The newer Hamilton Building was built to accommodate the museum's growing collections. The museum commissioned Daniel Libeskind, who collaborated with Denver-based Davis Partnership Architects, to design the 146,000-square-foot building, which is covered with 9,000 titanium panels. Libeskind, known for his designs worldwide, is the master planner for the World Trade Center site in New York; the Hamilton Building is the first Libeskind-designed building completed in North America.
Shortly after the Hamilton Building opened, a series of big storms hit Denver, and the building developed leaks in its atrium roof and skylights. Temporary repairs were used to stop the leaks in 2006 and 2007, and in 2008, the museum decided to reroof the leaking portions of the roof systems.
Black Roofing Inc., Boulder, Colo., was hired by M.A. Mortenson Co., Minneapolis, the project's general contractor, to reroof the 180-square leaking portions of the Hamilton Building's roof systems, which consisted of an upper roof area with a 6:12 (27-degree) slope and larger main roof area with a 10:12 (40-degree) slope. Work was scheduled to begin April 2009.
Complex execution
Before Black Roofing began work on the Hamilton Building, it participated in six sessions to plan crew safety, public safety, job management and job strategy.
"We had only seven months to complete the project and could not be late," says Tim Black, Black Roofing's president.
Working from custom-built scaffolding, crew members tore off the building's existing temporary EPDM roof systems, which consisted of 8-inch-thick insulation and a cover board, down to the 3-inch-deep steel deck.
"We designed and built 24-inch-wide 18-gauge galvanized scaffold support platforms to hold 40 12-foot-long by 24-inch-wide planks," says Jamaca Hubbard, Black Roofing's project coordinator. "We had more than 30 tied-off workers on the roof coordinating tear-off and reroofing simultaneously."
As the existing roof systems were torn off, crew members installed mechanically fastened 1/2-inch-thick DensDeck® Roof Board, water-based primer and Grace Ultra underlayment to the deck. Next, they installed 7 1/2- by 13-foot steel frames, which were lifted by crane to the roof and attached with 2 1/2-inch screws through L-brackets. The frames were installed in horizontal rows every 15 feet.
In the spaces between frames, the crew installed two layers of Hunter Panels' 4-inch-thick polyisocyanurate insulation—a total of 8 inches—to the roof board with urethane adhesive. Over the insulation and steel frames, 1 1/2-inch-deep acoustic B-deck was attached with the flutes running from eave to ridge.
Next, crew members installed a flat 20-gauge galvanized sheet-metal sheet with wide screws followed by 1/2-inch-thick DensDeck Roof Board, which was attached to the flat sheet with screws.
"The sheet was installed to provide a surface where screws would not miss the flutes," Black says.
Finally, workers adhered an 80-mil-thick custom-colored Sika Sarnafil roof membrane.
Workers also opened up the parapet walls, filled in the wall gap below with sprayed-in-place foam and installed an air barrier made of 20-gauge sheet metal and EPDM.
Waterproofing issues
Millions of dollars worth of artwork are located under the Hamilton Building's upper roof area, so Black Roofing could not have any leaks during the project.
"There are three large skylights we had to temporarily waterproof as the skylight subcontractor removed the old frames, installed new curbs, and filled in and decreased the size of the biggest skylight, which was 60 by 20 feet, with new decks and curbs," Hubbard says. "M.A. Mortenson built diversion walls to deflect water coming down the roof away from the skylights, and we developed a tarp system that instantly could cover the skylight areas if a storm developed."
The tarp system consisted of 36-mil-thick FiberTite® membrane with 8-inch Velcro® strips glued on the tarp's side laps so they quickly could bond to the vertical laps by simply removing the release tape.
"The tarps were done in small sections to allow us to open up small areas," Hubbard says.
Each day, a Black Roofing crew member was designated to keep constant watch on the weather radar. If rain was projected, the crew could cover the roof areas in 15 minutes or less.
"We also used $35,000 of EPDM material for temporary waterproofing in the field," Hubbard says. "The tarps work great over skylights, but in the field we had to glue side laps, gutters, etc., so we used new EPDM every day. Several times, when we had structural issues, we opened up an area six to 10 times before we got it right. We used about 450 squares of EPDM on a 180-square roof just for temporary waterproofing."
Public exposure and safety
For various reasons, safety during the Hamilton Building project was paramount.
"The job was extraordinary from the point of public exposure," Hubbard says. "M.A. Mortenson erected a seven-story, 150-foot-long protective scaffold over the front entrance, which is directly below the roof areas we were working on. Hundreds of people cross through that entrance every day.
"We had three issues we constantly faced: the crew's safety, crane safety and the public's safety," she continues. "Not one thing could fall to the ground, come loose or appear to be out of control."
To meet specific safety requirements, Black Roofing installed multiple permanent roof anchors to which workers tied off.
"Installing enough rope anchors for all the workers and meeting safety requirements was a big challenge," Black says. "Sorting out the ropes to work efficiently was our next biggest challenge."
Efficient trash removal also was necessary to ensure safety. Workers hand-collected and vacuumed all debris to ensure nothing fell to the ground. Debris then was placed on tarps and lowered to the ground with a crane.
A special honor
Black Roofing completed reroofing the Hamilton Building on schedule Oct. 20, 2009.
The company won NRCA's Gold Circle Safety Award for its work on the Hamilton Building. The Gold Circle Safety Award is not a nomination category but a special honor awarded by the Gold Circle Award judges for accident-free projects where public protection challenges were in the forefront of the job elements and dominated the scope of work, demanding creative safety solutions, implementation of uniquely challenging safety procedures or extensively involved multiple trades.
"This was a job of unparalleled complexity," says Steve Moosman, district manager of Sika Sarnafil Mountain Region, Salt Lake City, which nominated Black Roofing for the award. "It required detailed execution from an experienced team, including more than 20,000 man-hours for 180 squares. From conception to completion, this proved to be a unique job that handled numerous complex technical issues requiring skilled innovative solutions."
Ashley St. John is Professional Roofing's associate editor.
Project name: Denver Art Museum's Frederic C. Hamilton Building
Project location: Denver
Project duration: April 2009-October 2009
Roof system type: PVC single-ply
Roofing contractor: Black Roofing Inc., Boulder, Colo.
Roofing manufacturers: Georgia-Pacific Building Products, Atlanta; Grace Construction Products, Cambridge, Mass.; Hunter Panels, Franklin Park, Ill.; Seaman Corp., Wooster, Ohio; and Sika Sarnafil Mountain Region, Salt Lake City
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