Poinciana, Florida's earth-sheltered Reedy Creek Elementary School building is completely concrete. The 65,000 square-foot complex includes precast columns and beams, 12-inch-thick exterior walls, a 4-inch-thick floor and a 10-inch-thick roof slab. Except for entrances and classroom windows, it is completely covered with 2 feet of earth even though it was built entirely above grade.
Because of the high water table at the site, prior to construction the topsoil had to be cut away and an 18-inch-thick earth pad built with fill dirt hauled in from off-site. After the building was in place, a polyurethane waterproofing membrane was applied. The one-part, fluid waterproofing required no mixing or heating, but still formed a seamless, elastomeric "skin" bonded to the concrete. So as to be compatible with this urethane waterproofing, all exterior joints were caulked with a multi-component, high-performance epoxidized polyurethane sealant. The waterproofing membrane was then overlaid with 1/8-inch-thick protection board, followed by two 3/4-inch layers of urethane insulation and 2 feet of earth cover.