When you’re responsible for housing the data center operations for the Southeast’s largest concentration of telecommunications companies, the words “leaky roof” are likely to cause you more than just a little anxiety. So when a renovation contractor requested that Terracon provide a roofing evaluation and specification to reroof the 10-story, 103-year-old 56 Marietta Street building in downtown Atlanta, it was clear that this project would require special attention. The historic brick hotel built in 1912 is now home to a 160,000-square-foot data center. The U-shaped building has four different levels of roofing which cover approximately 13,000 square feet. The third floor was Terracon’s particular focus and proved to be an unique opportunity for roof consultation.
The project’s challenges began to mount early in the discovery phase. Terracon began by conducting destructive testing which identified that the building actually had two roofing systems – one of which was coal-tar pitch that dated back to the original construction. Coring roof samples then revealed that water had been running under the most recent roof system – a 15-year-old modified bitumen system. A subsequent moisture scan showed the third floor roof to be 100 percent wet.
The roof previously was retrofitted with platforms to mount air-conditioning units, and conduit-filled fiber cables and wires. These units could not be moved, and the roofing project had to be done without interrupting their function. The platforms rested 4 feet or less above the areas to be addressed, which required everyone involved to work on their hands and knees for the removal and replacement. Normal building operational requirements included zero tolerance for dust creation, strict building security and access limitation, and a simultaneous façade renovation which meant no extra activity could be conducted outside the building. Asbestos abatement was also required on the wall flashings and the 90 pitch pans.
Removal of the existing modified bitumen roof system began in January 2013 with the crew tearing off the existing roof, bagging the contents, and transporting each bag off the roof via the elevator. The crew used torches to dry off the surface of the old coal tar before the new hardboard could be installed. The hardboard was attached with insulation adhesive. Installing the substrate was slow work as it had to be immediately covered with membrane to protect it from inclement weather. Night tie-in was crucial in order to keep existing water in the old roofing system from migrating under the newly installed sections. The coal-tar membrane was kept in place to serve as a vapor barrier for the new roofing system – a fully adhered .090 inch thick (ethylene propylene diene terpolymer) EPDM roof membrane. The EPDM was selected because of its track record for durability and easy maintenance. The membrane was installed on high density, 120 PSI (pounds per square inch), closed-cell polyisocyanurate foam core cover board. The system was designed to allow for a 25-year manufacturer’s warranty with puncture protection.
OTHER UNIQUE ISSUES
The age of the brick façade also became an issue. New fasteners were substituted for the original fasteners to secure plywood and the new counter flashing to the parapet walls which rise abovethe roof line. These better secured the plywood to the 100-year- old brick. A three-month delay in the work schedule occurred because new platforms for the HVAC units had to be installed above the third floor roof area. New equipment was installed and existing equipment was relocated onto the platforms before work could resume. In March 2014, the work was completed, inspected, and warrantied by the roofing manufacturer. The building was dry with no leaks for the first time in 15 years. The cost to complete the roofing came in under budget, meeting a key objective of the owner and Terracon.
Terracon played a critical role in the project’s success by evaluating alternatives, recommending solutions, and overseeing the installation of an extremely challenging replacement project. Key to its success was the constant communication and cooperation among Terracon, the project manager, the roofing contractor, and the material manufacturer to recognize and address issues as the work progressed.