un shelves, for the most part, are easy to engineer and build. Rarely do they affect the engineering or construction process. There are, however, some points to consider:
• Watch the frost line. Steve Chandler’s area undergoes freeze/thaw conditions. This can prove worrisome for a shallow body of water such as a sun shelf because it sits above the frost line. “When you’re building close to the surface, you have to make sure the subsurface isn’t going to affect the structure when the ground freezes or when the pool freezes,” says Chandler, president of Custom Pools & Patio in Boise, Idaho.
To address this concern, he anchors the shelf. “We build a 2-foot-deep footing around the perimeter of those shallow areas so that we make sure we’re below frost level,” he says. “Otherwise, with the bottom of the pool sitting above the frost line, the freezing underneath could affect that structure.”
• Seek outside help in poor soil areas. You should do this with any pool, Lynn Forrest says, but sun shelves will need special attention because they run the additional risk of weighing too heavily on the bond beam. “Maybe you’re extending it out too far off the beam of the pool and it could actually be sort of a counterweight where it could actually try to break away from the pool beam itself,” says Forrest, president of Aqua Classic Pools & Spas Inc. in Clute, Texas. He has an engineer look at every pool he builds. The engineer might have him do anything from using larger rebar to installing a double mat of it.
• Say no to rebound. Like steps, sun shelves present a tempting opportunity for burying rebound, that byproduct of guniting or shotcreting when pieces of concrete-covered aggregate fly away. Burying rebound in the gunite structure takes away from the shell’s monolithic nature, so do not do it.
