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A four-step spray foam roof system eliminates leaking issues for Philadelphia Water Department building

The Right Treatment

A Four-step Spray Foam Roof System Eliminates Leaking Issues for Philadelphia Water Department Building


The Philadelphia Water Department’s (PWD) function goes way beyond providing water to the homes and businesses of the city made famous by Rocky Balboa and cheesesteak sandwiches. Before the water can be distributed, the PWD tests it for quality so that the end-user receives the highest-grade potable drinking water possible. In fact, a recent report produced by PWD’s product quality exceeds the standards developed by the EPA to protect public health.

This testing process is carried out inside PWD’s central laboratory building that solely operates in this capacity. As unequivocally important as this testing process is, it is also of equal importance that the water being tested does not get contaminated with infiltrating water. The testing building’s roof deteriorated with age. Even though PWD tried to repair the roof on previous occasions, it was never properly sealed and leaking remained constant in different areas of the building. At long last, PWD figured it was time for a quick solution that warranted long-term performance. PWD then found their coveted restoration in the form of a spray polyurethane foam roof system. PWD brought in spray foam specialists JJD Urethane, a company with which PWD had a long-standing relationship.

The first step in the restoration project involved the removal of the original roof system, which consisted of an EPDM substrate with river rock ballast aggregate and two-inch ISO board over steel decking. JJD brought in a twelve-man subcontracting crew for the removal of the roof system. A six-man SPF crew from JJD would later join the tear-off crew. The JJD crew was able to inspect the project area before and during the removal process. Upon inspecting the original system, the JJD crew noticed that the system was in utter disarray. Aside from the typical signs of wear-and-tear, the crew noticed that the ballast had been applied on too heavily and added excessive weight, which crushed the ISO boards underneath and caused them to loosen and fall apart.

“The roof system was completely unstable,” said JJD’s John DiNenna. “A combination of the weight of the ballast and people walking on the roof coupled with age had caused the EPDM to stretch and give way to cracks. A spray foam roof system was exactly the cure for this mess.”

After removing the original system, the tear-off crew installed SECUROCK Gypsum board to the steel decking, utilizing screws and fasteners to secure the board to the substrate.

When the tear-off crew would go off site, the JJD crew punched in, working on the areas that were ready for foam installation. They parked their rig on the side of the building and pulled their hoses onto the roof. The crew used two machines for the spray foam application: a Graco H-20/35 for the detail work and a Gusmer H5 proportioner for the bulk of the field installation.

In certain areas of the building, there were parapet walls that were high enough to provide fall safety for the crewmembers. However, for most of the roof the crew used perimeter flagging. Additionally, the crew masked 1,400 lineal feet of cap flashing that circled the entire building to protect it from overspray damage.

For the spray foam application, the JJD crew installed to the ISO boards two inches of Bayseal, a 3 lb. spray polyurethane foam made by Bayer MaterialScience.  The crew utilized 6-by-10-foot burlap windscreen to mitigate overspray damage while the foam was applied. The crew installed 18 sets of foam, which totaled a spray area of 24,000 square feet.

“The spray polyurethane foam was able to seal all the areas that had previously been leaking,” said DiNenna. “It will also provide insulation, which is something that the building never had before and PWD was very concerned about. The water testing staff will benefit from insulation in terms of comfort and energy efficiency.”

After the spray foam had cured, the JJD crew used a Graco Xtreme 45:1 airless spray pump to apply a 20-mil base coat of SCM3400, a medium-gray silicone coating made by General Electric (GE). Then, the crew used an additional Graco Xtreme 45:1 pump to apply a 15-mil topcoat of GE’s SCM3405, a tan-colored silicone coating.

The JJD crew then stocked their crane with a 700 lb. blast pot that attached a 250-foot, 1.5-inch supply hose that was used to broadcast 3-M Buff colored granules at the rate of 40 pounds per 100 square feet over the silicone topcoat. The crew then used a backpack blower to pile up and later dispose of all the loose granules that did not get embedded into the topcoat. DiNenna noted that it was vital to clear off the roof from any roof granules because loose granules tend to get into the drain system and can eventually block roof drainage.

For the final step of the project, the JJD crew was asked by PWD to install walkways, so that when it was time for the HVAC installation, the HVAC subcontractoring crew could perform their work without damaging the recently installed roof system. The walkway system consisted of installing 3.5 gallons per square of a light grey silicone coating made by GE to contrast from the tan topcoat and then hand broadcasted different color granules at 50 pounds per square onto the wet silicone. The JJD crew made the walkways 3 feet wide and installed a total of 750 feet of walkways throughout the roof.

“The walkways provided the roof with added safety so that people installing or servicing mechanical units didn’t walk around areas that could potentially damage the roof system,” said DiNenna. “The different colors of the coating and granules accentuated the walkways, making them clear for all to see. Even though this spray foam roof system is going to last over 20 years no matter who is walking on it, the walkways added an extra degree of protection from wear-and tear to the SPF roof system.”

DiNenna and his crew were on site for almost six weeks, at which point the project was completed. He said that PWD was very pleased with their work and valued the fact that the spray foam roof included a 20-year service warranty.

“This is a waterproof system that is guaranteed for 20 years with a renewable contract for another 20 years,” said DiNenna. “What’s not to like?”

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