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2015SummerShotcreteEMag

Swimming Pool Penetrations By Jonathan E. Dongell Sattention to detail in application that ensures is inevitable for most monolithic structures. -crete, a certain amount of shrinkage and separation around penetrations subsequent to applicationhotcrete swimming pools, spas, and waterfeatures require a proper mixture design and watertightness. A good shotcrete structure, Therefore, all penetrations should be sealed or enhanced with a good interior finish coating, plugged. Some interior finishes that are continually should not leak water. While the shotcrete can be trowelled to a hard, smooth finish may be capable engineered and placed in a manner that creates a of sealing around penetrations. Others, such as structure that is watertight, it is an unrealistic exposed-aggregate finishes, may require that a sea- expectation that shotcrete will be watertight at lant or plugging material be applied prior to applying penetrations or where it butts up to a dissimilar the interior finish coating. It is common practice to material. Swimming pools are typically shot dig out (“cup out” or “box out”) the shotcrete around monolithically, meaning one continuous applica- some or all penetrations. Typically, dig outs for return tion, with no relief joints. Therefore, it is logical lines are a nominal 1.5 to 2 in. (38 to 50 mm) in that some separation will develop at penetrations, depth by a nominal 3 to 4 in. (75 to 100 mm) around primarily as a result of normal shrinkage that the piping. Suction lines may require a much larger occurs during the setting of hydraulic cement in dig out, depending on the type of main drain base shotcrete. While the function of an experienced ring and cover that will be installed. shotcrete nozzleman is to fully encapsulate piping, Dig outs allow better access to the piping, light niches, and other penetrations within shot- making it easier to cut the pipe far enough back to ensure that fittings will be flush with the anticipated surface of interior finish coating. Dig outs also allow access and space to apply a sealant or plugging material around the penetrations, ensuring they will be watertight. Other penetra- tions that require no other adjustment or work to be done prior to the application of the interior finish coating may often have little or no dig out. The burden of ensuring penetrations are sealed and/or plugged may fall to the builder, plasterer, or the pre-plaster prep crew depending on which party is given the responsibility. Ideally, the engi- neer or architect should stipulate the sealing or plugging of penetrations in a manner that ensures Fig. 1: Water intrusion at penetrations from all are watertight. behind structure Fig. 2: Piping with and without fitting prior to sealing Fig. 3: Piping with fittings and sealed 10 Shotcrete • Summer 2015


2015SummerShotcreteEMag
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