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2016WinterShotcreteEMag

2015 Outstanding Pool & Recreational Project Reflecting on a Shotcrete Pool By Ryan Oakes Dry-mix shotcrete—also known as gunite— has a bad reputation in some parts of the structural shotcrete industry, as well as in the pool marketplace. There are a multitude of reasons that contribute to this perception, but foremost is the lack of education on the side of the specifiers, the contractors hiring the shotcrete crews, and sometimes even the crews and the company owners. It is amazing that so few people with so many years of experience in their trade don’t know why past failures exist in their trade, particularly in shotcrete, both wet and dry. While this article is not about the industry's shortcomings, it is a relevant preface to why we were called into the project that this article is about. In short, a pool had been shot and failed miserably. While the owners were sorting out the problems with the previous pool builder and the dry-mix shotcrete installer, time passed and the home construction continued. By the time Clearwater Construction Group, Inc., was called in to both finish demolition of the previous work and build the new pool, there was a really nice home on one side and on the other three sides, a 40 ft (12 m) drop to the ground, with a 400 ft (120 m) slope down a mountain thereafter! Minimal access was available on one cliffside so between wheelbarrows through the house and a track loader on the cliff side, over 60 tons (54,000 kg) of remaining demolition materials were hauled away. A Fresh Start Subsequently, a clean slate remained: a suspended sub-slab, in excellent condition, cantilevered over 40 ft (12 m) tall concrete walls. The new pool was to be built just as the original had been designed. Because it was being built on the sub-slab, the three vanishing-edge sides of the pool would be fully exposed to the elements and partially exposed to the viewer. The exterior surface is slated to be covered in a stucco product to match the color of the stone on the home and the interior of the pool is completely surfaced in black 0.75 in. (20 mm) glass mosaic tile. On the side of the pool that touches the decking, a Lautner’s edge detail was used to create the illusion that the water meets the top surface of the adjacent Travertine decking material. This detail involves finishing a delicate knife edge during the shotcrete process that separates the pool water from a hidden gutter, which carries the overflowing water back to the equipment room. In this case, the equipment room is underneath the pool. To install this edge during the shoot, we brought along extra finishers. In fact, we had several extra helpers on this project due to all the detail work required (Fig. 1). Overall, there were over 90 ft (27 m) of vanishing edge, over 40 ft (12 m) of the Lautner’s edge gutter, and a perimeter overflow spa, along with two sets of steps, an underwater bench, and two large shallow-water lounging areas (Fig. 2). Understanding the technical nature of the pool and the difficult logistics, we planned on this being a multiple-day shoot. Leading up to the shoot, Clearwater Construction Group formed the project with extremely rigid framing so that we not only had a good surface to shoot to but also to walk on and navigate around without fear of falling or damaging formwork. Safety lines were run on the outside of the project so that any finisher who had to step out of the pool could clip in with their safety harness. The reinforcing bar, all No. 4 (No. 13) steel, was well-placed and tied so that it, too, could be walked and climbed on with minimal movement in the steel. There was a great deal of plumbing to shoot around, including a 6 in. (150 mm) trunk line with vertical risers every 5 ft (1.5 m) for the overflow water. The spa plumbing was very intricate and required a great deal of care and skill in placing the shotcrete around the pipe and fittings well. Finally, we were given a 1/32 in. (0.8 mm) tolerance to hold on the vanishing edge to reduce the amount of water needed to flow over the edge (Fig. 3). A New Perspective Pools have forever been plagued with efflorescence, water-retention problems, and installation complications. Particularly, vanishing-edge pools with at least one side of the vessel being exposed to the elements and not hidden in earth 24 Shotcrete • Winter 2016


2016WinterShotcreteEMag
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