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COATINGSPRO MARCH 2017 57 Luckily, the Pentens materials can tolerate high temperatures and high humidity during the application process. "Since it was an open roof deck, we couldn't fight against the weather. We could only choose an epoxy primer that has a wide tolerance to the substrate moisture and apply a layer of epoxy sealer to seal off the substrate and act as a moisture barrier," explained Wong. ey had another trick up their sleeves, too: "We also mopped the substrate often to remove surface mist or dew before spray- ing the polyurea," he said. And as for the thunderstorms and typhoons, the crew was very lucky — there were no typhoons during the project, nor was there a series of really wet days. is was a huge win for the crew. "In Hong Kong, the weather changes very fast. Sometimes it's sunny in the morning but is raining by afternoon. We were very lucky that the rain didn't affect the schedule too much since the schedule was already very tight," said Wong. e project began on June 17 and needed to be wrapped up by July 10 — before the end of the summer holiday and the start of the new term. at's less than one month to give this school a new roof. ank goodness for this A+ crew! With parapets and a security fence surrounding the roof's edge, at-height safety equipment wasn't necessar y. Because of the high humidity and heat, though, the materials did need to be able to tolerate moisture. To the substrate, the crew rolled on Pentens E-500SE primer at an average of 0.3 mm (11.8 mils) and then they troweled on Pentens E-501S putty filler at an average of 0.5 mm (19.7 mils). JOB AT A GLANCE PROJECT: Applied polyurea waterproofing materials to the concrete roof of a school located in Hong Kong COATINGS CONTRACTOR: HKP Engineering (Materials) Limited Room A3, 2/F, Block A, Proficient Industrial Centre 6 Wang Kwun Rd. Kowloon Bay, Kowloon Hong Kong +852 6178 2225 www.hkpmaterials.com SIZE OF CONTRACTOR: 15 employees SIZE OF CREW: 2-7 crew members PRIME CLIENT: Christian & Missionary Alliance Sun Kei Primary School (Ping Shek) 12 Clear Water Bay Rd. Kowloon Hong Kong +852 2342 3322 www.sk2.edu.hk SUBSTRATE: Concrete, roof tiles, and existing membrane CONDITION OF SUBSTRATE: Suffering from wear and tear, in need of rehabilitation SIZE OF JOB: 8,000 sq. ft. (743.2 m²) DURATION: 24 days UNUSUAL FACTORS/CHALLENGES: » The extreme heat and humidity of the summer months in Hong Kong meant that the materials had to be tolerant of moisture on the substrate. » The substrate was mopped often to remove surface mist or dew before spraying the polyurea. MATERIALS/PROCESSES: » Prepped the surface using a blower, vacuum, and 3,000-psi (20.7 MPa) pressure washer to clean the substrate » Roller applied the Pentens E-500SE primer at ~0.3 mm (11.8 mils) » Trowel and scrape applied Pentens E-501S epoxy putty filler at ~0.5 mm (19.7 mils) to the entire roof area » Spray applied Pentens SPU-1000 polyurea at ~2.0 mm (78.7 mils) using Graco Reactor 2/E-XP2 » Spray applied two coats of Pentens NPU-12 polyurethane at ~0.1 mm (3.9 mils) each, using airless spray equipment SAFETY CONSIDERATIONS: » Did not need to wear fall protection » Wore safety helmets, Tyvek suits, 3M 6000 Series half-face mask respi- rators, anti-slip safety boots, and MAPA professional gloves