Do you remember in "It's a Wonderful Life" when Jimmy Stewart and Donna Reed fell into a pool hidden underneath a retractable gym floor? Here's the scene to refresh your memory.
The place actually exists. It's called, fittingly, the Swim Gym, and belongs to Beverly Hills High School in Los Angeles. Here's how it works: The court is divided along the centerline, and each half is anchored to rows of two-by-fours atop steel I-beams. The court "opens" at the turn of a key—motors roll the platforms underneath the arena bleachers, where huge exhaust fans mitigate moisture. Then, 5 feet below, a 25-yard swimming pool appears. The floor in the movie has been lost to time, but recently Pacific Floor installed a new maple court in the space. Because the gym hovers around 60 percent humidity, Pacific Floor acclimated the flooring material longer than usual and installed it with a moisture content around 9%, says Sales Manager Mark Herthel. With the court "closed," the crews installed a 15-mm-thick vapor barrier, 9⁄16-inch-thick resilient padding and ¾-inch-thick plywood anchored into the retractable platform using steel channels. Then 1½-inch-wide maple flooring chosen for its stable vertical grain was installed. Pacific Floor closed off the sides of the subfloor using stop blocks and closed cell foam underlayment to prevent moisture from creeping up the side of the court. Before the flooring was sanded and finished, the crew sawed the court in half along the centerline and installed a 4-inch stair riser as nosing on both halves. For durability, they also placed an aluminum plate on the face of each platform where they meet. The installation went much more smoothly than the dance scene in the movie. Nothing—man, woman or machine—fell in, Herthel says.