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Pool & Recreational Shotcrete Corner Commentary on Watertightness and Waterproofing of Shotcrete By James Scott Over the recent years, the idea of water- after there has been a large failure, or series of(submerged conditions). If you keep your ear tothe ground, it appears that these changes comeproofing has taken a more prominent rolein the construction of higher-end pools and other watershapes—and the debate on this topic smaller failures. It has caused the providers to seems to be on the increase. Most of us in the pool look more closely at what is happening between industry are at least peripherally aware of a broad the marriage of their product to the substrate or debate as to whether waterproofing should be other products. used, and in what situations. It does not mean that these waterproofing From my observation, this issue is due to the products do not work per se. What it does point increasing demand and interest in the higher-end out is that there is a huge volume of chemically swimming pool—what features can be incorpo- based products being used in partnership with rated, as well as architectural elements that can other chemicals or cementitious-based products be achieved. Clearly, many pools are no longer without years of practical field experience. And, just the typical single body of water with a simple many times, these products are underlayments for ceramic waterline tile band and marble plaster expensive finish materials, such as tile and stone. finish. Many forces continue to act on the industry, Ultimately, we can divide the use of water- such as development of product lines; increased proofing into two (non-mutually exclusive) availability of automation; huge building booms; situations. The first occurs when tile (or similar) information availability; and, most significantly, is used for the interior finish. The second follows proliferation of ideas through houzz.com and when a shotcreted pool or vessel is not shot well, similar websites, along with world travel. and is not watertight (refer to Fig. 1 and 2). In many ways, the swimming pool industry is In the tile industry, waterproofing is an integral still a young industry. The residential pool part of the industry standards.1 In fact, two types industry in the United States is particularly of waterproofing are separately referred to as “young” in that it has been largely unregulated, cementitious and membrane. Even if the pool is and the barrier to entry has been low. Critically, already watertight or even waterproof from a architects and landscape architects are particularly cementitious standpoint, the waterproof mem- ignorant of swimming pools and how they are brane is sometimes still used to act as an anti-fracture built. Therefore, unregulated pool builders layer for glass or other fragile tiles. It is important drive construction practices and techniques. As to note that many waterproofing products, applied competition increases, prices are driven down and to the inside of the pool, do not act as water- ultimately quality suffers. There is not a natural proofing for negative hydrostatic pressure (that checks-and-balances system between the architect is, water penetrating from outside the pool shell). and builder. It is still widely misunderstood that a plaster Not only are pool builders experimenting with interior finish will act as a “sealing coat” or water- new materials, products, and techniques but proofing, which is fundamentally untrue. A multinational companies are also marketing their properly shotcreted shell needs to supply the products to the pool industry and thus are watertight properties for the pool. “experimenting” via the builder’s use. If you put The ASA Pool and Recreational Shotcrete all of this history and set of factors together, it’s Committee speaks to watertightness in Position easy to see how shotcrete installation can suffer Statement #4.2 “Watertightness of the shotcrete and how “waterproofing” has become appealing. material is a crucial durability and serviceability Of note have been the changes and about-faces property of any properly constructed water- in some manufacturer’s directions for the use of holding shotcrete structure. Shotcrete placement their product in swimming pool construction that allows water to pass through the concrete of 56 Shotcrete • Fall 2015


2015FallShotcreteEMag
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