Plaza VII Office Building

Minneapolis, Minnesota

Plaza VII Office Tower is a prestigious office facility located in the heart of downtown Minneapolis. The building was built in 1987, is 475 ft. tall, and consists of 37 stories of quality office space. The owner Carlson Real Estate Company is one of the top rated property management firms in the country.

On a yearly basis, Roof Spec, Inc. performs roof evaluations of all Plaza VII roof levels. Each roof assembly is evaluated to identify any deficiencies. Recommendations based on the condition of the roof assemblies, with budget forecasts for maintenance or replacement, are then supplied to the owner.

In 1998 and 1999, Roof Spec was instrumental in the design and construction administration of the 35th and 37th floor roof assemblies which total an approximate area of 14,000 sq.ft. The roof system designed and installed was a fully adhered EPDM roof membrane.

When asked to design the new roof assembly, we had to combat a long standing problem of high internal building pressure. This issue appeared to be the cause of the previous roof failure. To overcome the concern, we incorporated multiple functional layers into the roof system. After removal of the existing roof down to the poured in place concrete deck, we specified that a self adhering membrane be installed at the joint between the deck and the wall. A 1/2” Dens-deck was fastened to the concrete deck. One ply of self adhering membrane was installed continuously over the Dens-deck. The combination of Dens-deck and self adhering membrane provided a “pressure barrier” to eliminate the potential of “billowing” or detachment as had previously occurred. This was followed by the tapered isocyanurate insulation and a 5/8” thick OSB which was mechanically fastened at a rate equal to that of FM 1-120 requirements. A 60 mil EPDM membrane was then fully adhered.

Due to the tenant’s extreme sensitivity to noise, all roofing work was accomplished during the night. To accomplish this, the contractor had to incorporate several light stands placed throughout the roof area to sufficiently view the work in progress.

Another hurdle that had to be overcome was removal of the existing roof debris. The facility was too tall to crane any material, so it all had to go through the building interior. Through coordination between Carlson Real Estate, Roof Spec, Inc., and the roofing contractor, we were able to protect the building interior on a nightly basis. Removal was performed every night without exception and the efficiency of the roof project was not compromised.

All of these factors, and the incorporation of a sound roof assembly design, led to a successful project completion.