THE DALLAS MERCANTILE - A HISTORIC LANDMARK IS TRANSFORMED

The 1940s Mercantile National Bank Building was the only major skyscraper constructed in the U.S. during World War II. Since then, the building and its occupants have seen their share of tumultuous times. After the economic downturn in the late 1980s the Mercantile National Bank Company merged and dissolved. The complex was eventually abandoned in 1993. Fifteen years later, Forest City Enterprises struck a deal with the City of Dallas to receive substantial financial incentives from the City in order to rehabilitate the building.

Hensel Phelps, the general contractor for the restoration project, hired Chamberlin Roofing & Waterproofing to complete the roofing restoration portion of work on the building. As part of the exterior renovation, Chamberlin’s scope of work focused on creating a watertight rooftop while the building was being converted into luxury apartments and retail space.

Installation of Two Roof Systems with Limited Access 

“The Merc,” as it is called, is historic and had also been abandoned for over a decade. These special circumstances offered construction obstacles Chamberlin’s crews had to address quickly in order to complete the work on time. The first obstacle was the installation of a temporary and permanent roof system with limited access.

Chamberlin’s primary job on The Merc was removing existing tar and gravel built-up roofs and replacing them with a fully adhered TPO roofing system, which was covered with a custom pedestal and paver system. With over 15 roof areas to be renovated while various trades worked continuously on other exterior renovations and abatement, it became necessary for Chamberlin to remove the original roofs and install temporary ones. This allowed other contractors to continue their work without damaging the new roofing system while keeping the interior of the building dry. Temporary roofs were later removed and permanent roofs installed with a new paver system on top. 

 A temporary EPDM single-ply assembly, providing a watertight work surface for other trades was first applied. Then, a second and permanent application was installed using a white TPO membrane topped with concrete pavers. Further complicating the work that was already “double duty,” access to work on The Merc was anything but typical. “Normal” means of crane loading were not plausible, not even the use of a helicopter would work.

The job site mobilization equipment was limited to a one-man hoist that had a weight limitation of 1,500 pounds. Therefore, roofing materials and concrete pavers were moved in limited amounts, by hand, up the hoist, across rooms, up stairs, through windows and placed on exterior roof locations.

In addition, because The Merc is a historical building, all of the final terminations for the TPO membrane had to be hand prepared to protect the adjacent surfaces in order to preserve their natural aged appearance. Concrete pavers were then installed, not only to provide exterior weather protection, but also to transform the roof areas into outdoor community terraces.

Hazardous Material Removal

In addition to the obstacles limited access created, Chamberlin was also faced with the challenge of removing hazardous materials. During the initial building investigation asbestos was discovered in the wall flashing. In order to meet new building code requirements some roof locations required abatement.

As the asbestos in the wall flashing not friable, Chamberlin was able to self perform the removal process; a process that involved separating the contaminated from the non-contaminated materials. Contaminated material was bagged and placed in a container specifically designed for hazardous material, which was emptied at the end of each day. Non-contaminated material was placed in burlap sacks and hauled to ground level where it was placed in job site dumpsters.

When work wrapped up on The Merc, Chamberlin had successfully overcome the unique construction obstacles associated with this historic site. Moreover, the company’s scope of work was completed on time, productively, and accident free. The new exterior roof renovations not only provided a watertight assembly but also offered paved outdoor areas essential to the amenities of the historic landmark, turned luxury living space.