Water intrusion can cause big problems for concrete structures. If those structures are not waterproofed properly, water can cause distress on the concrete, which can lead to fractures that will continue to grow exponentially as saturation of the material increases. A concrete surface with aging or inadequate waterproofing is in real danger of cracks, spalls, deterioration, rust spots, efflorescence, and other damage. A variety of durable deck coatings that will deter water damage and maintain a surface’s color, keeping it looking like new for years, are available. Modern technology has also provided materials for these specialty coatings that are ideal for suspended slabs, recreational roof decks, garages, patios, balconies, sun decks, areas around pools, and other areas that require a durable surface, such as the University of Minnesota’s indoor rowing practice tank. THE CHALLENGE Located on the banks of the Mississippi River, the two-story Irene Claudia Kroll Boathouse features a 35-seat “erg” (ergometer or rowing machine) room, a full locker room, boat storage, coaches’ offices, and an indoor 7500-gal. (28,000-L) practice tank on the second floor (Fig. 1). The facility was constructed in 2007 with precast concrete flooring planks and a nonstructural topping slab. The original waterproofing system beneath the tank was a standard 40-mil (1-mm) pedestrian polyurethane traffic coating. Over time, the system had begun to fail at the cracks and control joints in the concrete substrate, allowing water that had splashed or leaked out of the tank to seep through the existing flooring and leak into the space below. Faced with this problem, university administrators sought a long-term waterproofing solution that they would not have to worry about for at least the next 20 years. The university also had a tight time frame—winter break—for the work to be completed. 14 • IIBEC Interface October 2021 Figure 1. The University of Minnesota is one of the few universities in the United States to boast an on-campus boathouse. October 2021 IIBEC Interface • 15 INSTALLATION To meet the university’s needs, the waterproofing contractor selected a cold-applied traffic coating system that is ideal for pool decks, splash pads, fountains, and water features due to its durability, abrasion resistance, crack bridging, tenacious adhesion, and fast cure time—the latter feature makes it possible to open a coated area to traffic as soon as one hour after installation. The system also protects concrete from the damaging effects of chlorine, chemicals, oils, and other substances. Additionally, the system is forgiving, which allows installers to apply extra coats long after the previous coat has fully cured and to easily make repairs. The general contractor on the project removed the old tank, along with the failed waterproofing, and installed a new drainage system for a new tank. The waterproofing crew then repaired the concrete around the new drains, as well as cracks in the concrete slab where the water had leaked through (Fig. 2). The waterproofing contractor followed the manufacturer’s strict application guidelines to ensure that the coating system was placed properly, and also worked closely with the manufacturer’s representative to inspect the substrate before the coating was placed, as well as during installation. These precautions were important because abnormalities such as cracks and spalls in the substrate can lead to a faulty waterproofing application. Installers did encounter a change in the expansion joint material used after the old coating system was removed and the control joint material was opened up. The versatility of the cold-applied system allowed the team to install a complete waterproof flooring system that was integrated into the expansion joint for a full system warranty. The system comes with a 20-year warranty, but it will likely last much longer if applied and maintained correctly. The waterproofing contractor installed a 125-mil (3.2-mm), cold-applied traffic deck system with polyurethane-methacrylate technology (Fig. 3). This extremely durable system is designed for waterproofing concrete slabs and providing maximum water protection for occupied areas below. A challenge when working with cold-applied traffic coating systems is its strong odor. This was a particular concern in this case because the project was undertaken in a closed environment, so the waterproofing contractor took care to provide adequate ventilation in the area when installing the system. The traffic coating system included the following: • A methyl-methacrylate two-component primer for porous and nonporous substrates • A two-component, epoxy-based, solvent-free vapor barrier primer for concrete surfaces • A benzoyl peroxide-based powder used to react all components of the system • A modified polyurethane-methacrylate base Figure 2. The Minneapolis branch of the waterproofing contractor teamed up with a Minnesota-based general contractor to make repairs to the second floor of the boathouse where the practice tank is located. Figure 3. Workers apply the waterproofing coating in the University of Minnesota’s boathouse. coat (available in self-leveling, roller, trowel, and low-modulus grades) that bonds firmly to the primer and retains its integrity regardless of substrate movement up to 1/16 in. (1.6 mm). • A modified polyurethane-methacrylate base coat that bonds firmly to the primer and is compatible with a hot-applied, rubberized asphalt waterproofing membrane • A joint compound material mixed with an initiator • A modified polyurethane-methacrylate wear coat loaded with aggregate to give the system excellent impact, abrasion, and chemical resistance • A crystalline silica powder used in conjunction with a two-part, chemical-curing polyurethane-methacrylate wear coat • 16- to 20-mesh silica sand, color quartz, aluminum oxide (bauxite) • A methyl-methacrylate topcoat (available in a variety of colors) that offers excellent abrasion resistance, ultraviolet stability, and a chemical resistance system An in-house quality control program provided an extra layer of protection during the system’s installation. The waterproofing contractor ensured proper mixing of the materials and the correct application rate with every unit, using a mil-gauge to help promote a proper overall application. An electronic leak detection (ELD) test was used following the application to ensure that the coating system was monolithic and free from holes or discontinuities. An ELD test, however, cannot be used to detect variances in the application’s thickness. Once the coating system had adequate time to cure, the general contractor installed the new tank on top of the waterproofing membrane. MAINTENANCE Maintenance power washing of a deck coating is highly recommended and required by most warranties. Power washing should be performed at least twice a year. Those maintaining the system also need to understand that while the membrane surface keeps corrosive elements from reaching the concrete, the system is at risk if the corrosive elements are allowed to sit on the surface and the coating is breached, fails, or develops a crack. In those circumstances, the corrosive substances can easily penetrate the concrete. The coating system maintenance manual will give facility managers additional details on how to properly maintain the deck coating (Fig. 4). In addition to regular power washing, maintenance manuals also recommend routine visual inspections with the specialty contractor who installed it, plus give additional recommendations for extending the life of the deck coating, so it is wise to read the manual from cover to cover. Please address reader comments to elorenz@iibec.org, including “Letter to Editor” in the subject line, or IIBEC, IIBEC Interface Journal, 434 Fayetteville St., Suite 2400, Raleigh, NC 27601. 16 • IIBEC Interface October 2021 David Grandbois is assistant branch manager for Western Specialty Contractors—Minneapolis branch. David Granbois Figure 4. This photo shows the completed University of Minnesota boathouse project, with coating system and indoor rowing practice tanks in place. PROJECT TEAM Owner: The University of Minnesota Waterproofing contractor: Western Specialty Contractors General contractor: Gardner Builders
