Sense and sensitivity

• Photo courtesy of Garvey Roark Inc., West Chester, Pa.
• Photo courtesy of Garvey Roark Inc., West Chester, Pa.
• Photo courtesy of Garvey Roark Inc., West Chester, Pa.

A benefit of living in the commonwealth of Pennsylvania is it provides all residents with assistance regarding operating a business and living in the commonwealth, among other topics.

But the commonwealth was the one looking for assistance when it needed a roof system replacement for its Forster Street State Office Building, an office and parking garage facility in Harrisburg, Pa. The roofing contractor who took on the project would need to meet Pennsylvania's stringent design criteria, which includes a 20-year roof membrane system capable of withstanding ponding water for 72 hours and resistant to exhaust vapor emissions.

The most difficult issue to resolve would be that most of the building's interior space was without any type of ceiling, and as a result, there was no intermediate protection from possible debris during the scheduled roof system replacement. In addition, unusually large joint openings in the existing concrete plank deck further complicated the project.

The commonwealth of Pennsylvania invited Garvey Roark Inc., West Chester, Pa., to offer a bid proposal and detailed design for the emergency roof system replacement project. The 20-year-old roof system was leaking severely.

"We were asked to design and construct a 20-year roof assembly to meet the design criteria established by Pennsylvania's project architect and meet its expedited schedule in accordance with the emergency construction terms and conditions," says John Peck, estimator and project manager for Garvey Roark.

The terms and conditions included completion in 120 calendar days; providing a 100 percent performance and payment bond; and beginning work upon notice to proceed. The bid date was March 26, 2004, and the contract award was April 7, 2004, which meant mobilization had to begin almost immediately upon award of contract.

"We had to complete the project before bad winter weather began in November and December. It was an extremely accelerated 'fast-track' project. A bar graph schedule was submitted with the bid proposal, and the award was based on the best value for system design performance, schedule and price," Peck says.

Important decisions

The office building's original roof system was 200,000 square feet (18580 m²). The existing roof assembly consisted of a 4-inch- (102-mm-) thick concrete plank roof deck; 1/2-inch- (13-mm-) thick saturated wood fiberboard roof insulation; tapered expanded polystyrene insulation board (1 1/2 inches to 6 inches [38 mm to 152 mm] thick); and loose-laid EPDM membrane with rounded river ballast.

The tear-off required the removal of the smooth river ballast from the roof.

"We used vacuuming procedures to remove about 1,000 tons (907 Mg) of river gravel to be delivered to the owner for use in landscaping or road work at any of their state-operated facilities," Peck says. "We also temporarily ballasted the existing roof assembly with materials sufficient to prevent wind blow-off. We demolished all existing materials and put them in trash bins.

"We contacted several recycling companies who indicated the existing extended polystyrene [EPS] insulation had to be 100 percent clean without any contamination," Peck continues. "The existing roof system had been leaking for a few years, and after several core analyses, we determined the EPS was contaminated."

Garvey Roark then installed GAF Materials Corp. tapered polyisocyanurate insulation, which was adhered in hot asphalt to the primed deck to meet the existing tapered design and layout. GAF Stratavent® perforated vented base sheet was installed over the insulation per the manufacturer's installation requirements. GAF Everguard® Fleeceback 60-mil- (0.06-inch- [1.5-mm-]) thick TPO membrane was installed in hot asphalt for a required 20-year warranty, which included an 80-mph (129-km/h) wind-speed warranty. Metal-Era Anchor Tite Fascia was used at roof perimeters to provide additional membrane security.

During the project, material supply was coordinated efficiently.

"I kept in constant contact through e-mail and telephone calls with the roofing material supplier to coordinate anticipated material deliveries based on our progress," Peck says. "There was a significant amount of tapered polyisocyanurate insulation required for this project—20 trailer loads—and the insulation manufacturer was within 20 minutes of the job site, which helped."

The choice of using hot asphalt to adhere the polyisocyanurate insulation was a decision made after careful deliberation.

"Mechanically fastening the roof insulation was ruled out in the design consideration stages because of the potential difficulty in obtaining optimal production to meet the required accelerated schedule," Peck says. "And a ballasted roof assembly would not have met the criteria established by the commonwealth of Pennsylvania to meet an 80-mph [129-km/h] wind-speed warranty. A roof assembly applied with hot asphalt was selected to accomplish both requirements."

However, as a result of the hot asphalt application, safety for building occupants and vehicles especially was important because of the roofing materials being used.

"The hot asphalt seeped to the existing concrete floor of the parking garage facility through joints in the existing concrete plank deck," Peck says. "We established a daily safety perimeter zone, and a safety monitor beneath the concrete plank deck protected individuals and vehicles from the hot asphalt used to mop the new insulation. The monitor made sure nobody penetrated the safety zone area established below, which was marked off with yellow fluorescent caution tape."

The company decided not to strip the joints in the concrete plank before insulation was installed.

"Some of the joints contained roof cement and fabric from the original roof system, and we believed the existing joints were too wide to strip in because any felt paper would crack or split," Peck says.

No interruptions

Garvey Roark had to face the challenge of completing the roofing project while the building's daily activities continued.

"We had to be careful not to interrupt the daily operations of the facility, which included a full-service parking garage, army surplus store and extremely sensitive photographic laboratory," Peck says.

The laboratory contained valuable equipment, and Garvey Roark determined hot asphalt could not be used over that area because of the risk of damaging the equipment. The company instead adhered the first layer of polyisocyanurate insulation using a low-rise urethane adhesive. The adhesive was not used for the rest of the project because it was deemed too expensive, and the owner, because of a previous project experience, preferred hot asphalt application.

The company had to pay special attention to the weather when installing a roof system on the laboratory area.

"The 15,000-square-foot (929-m²) laboratory area was completed during a streak of hot, stormy weather in August," Peck says. "We had to pay careful daily attention to the weather forecast to successfully complete installation on this highly sensitive area.

"Severe thunderstorms or the threat of severe thunderstorms meant we could not proceed with roof removal operations," Peck continues. "Therefore, a lot of the work was performed on weekends or when nonthreatening weather was forecast so we would minimize risk to the sensitive interior. The summer of 2004 was rainy, and though the anticipated number of work days to complete the project was not affected, the overall completion time was affected by days lost because of weather."

Designing and installing an emergency roof system over an active parking garage was difficult, Peck says.

"The phase over the parking garage included relocating state-owned vehicles and personnel daily to provide adequate safety while installing the roof system," he says. "This included protecting people and vehicles from the hot asphalt seeping through the existing joints in the concrete plank deck when adhering the insulation. After each day's application was completed, our work area for the following day was blocked off and all vehicles had to be relocated. However, the entire area—the parking garage, service bays, army surplus area, car wash area and offices—still was fully operational during construction."

Meeting expectations

Garvey Roark appreciates the opportunity to be a part of the Forster Street State Office Building project.

"Achieving the goals established in the emergency construction contract and completing a quality-oriented roof system application was a rewarding experience," Peck says. "Meeting the stringent design criteria and fast-track schedule made the project even more satisfying."

Krista Reisdorf is managing editor of Professional Roofing magazine.

Project name: Forster Street State Office Building
Project location: Harrisburg, Pa.
Project duration: April 2004-August 2004
Roof system type: TPO membrane
Roofing contractor: Garvey Roark Inc., West Chester, Pa.
Roofing manufacturer: GAF Materials Corp., Wayne, N.J.