The 250 Plaza Building

ABOUT 250 PLAZA

The 250 Plaza building shares the evolving and growing skyline of downtown Milwaukee, shooting 20 stories up at the northwest corner of Wisconsin Avenue and Broadway. It’s a busy part of the city, with vibrant office, retail, and hospitality activity.

250 Plaza was built in 1973 and had a built-up gravel-surfaced roof that was restored around 2000.

SAFETY CONSIDERATIONS

The many building projects downtown often require partial street closures to accommodate construction vehicles and equipment, as well as pedestrian safety structures. Such was the case when it was determined 250 Plaza needed a new roof system.  It was a project well suited for FJAC’s capabilities, problem-solving, skilled craftsmanship, and equipment capabilities.  On the equipment end, FJAC was able to eliminate disruption to the building’s interior by utilizing its unique mobile tower crane which was set up alongside the building on busy Broadway.

EMERGENCY SITUATION

Unfortunately, part of Broadway was already blocked for a building project across the street, requiring a delay of the roofing project until after winter. But a critical situation meant that FJAC would need to take some immediate action.  “As part of our inspection and preparation work, we found the existing roof system to be completely saturated,” noted FJAC Vice President Brian Schaut.  “In essence, parts of the roof were floating; the existing vapor retarder was the only thing holding back the water.  The building otherwise showed no signs of major water problems, and basic observation of the roof wouldn’t show any issues,” he added. We immediately cored the roof to install pumps to remove the water, and then monitored the situation until the roofing project began,” Schaut added.

Rare Window Washing Track Restored – That system was removed entirely, but it was decided to keep another significant element atop the roof – an original track system that circled the building,  which was used to support window washing equipment. “The window washing track is one of the few in the city, but it wasn’t being used,” according to Superintendent Jason Gilbertson.  “The original plan was to remove it.”  That would have rendered the valuable window washing equipment useless and would have added track removal expenses to the total project cost.  Since the existing system was still functional, it was decided to restore it.

Derbigum Membrane and Resin Flashing Application – With the tower crane in place to bring down debris from the old roof system and lift new materials in place, the project was launched in spring.  Once the existing roof system was removed, the existing concrete deck was primed and covered with a new vapor retarder membrane installed in an asphalt-based cold adhesive.  New polyisocyanurate roof insulation was installed over the vapor retarder in a cold adhesive. A layer consisting of a combined Derbigum base sheet cold-applied in an asphalt based adhesive along with a heat welded Derbicolor modified bitumen granulated cap sheet, was finally installed to provide long-term protection from the harsh elements of Wisconsin’s four seasons.

Another Derbigum product was selected for flashing the window washer track system, which was anchored to the roof deck via concrete posts. The wash equipment track provided a critical area of concern due to numerous roof system penetrations for the structural support pipes.  “By using Derbigum’s Derbiflash, a liquid flashing resin, instead of convention pitch pans, we were able to provide a long-term solution matching that of the roof membrane itself.