When Joe Massaro bought Petra Island, an 11-acre patch of heaven across the water from his main residence in Lake Mahopac, N.Y., he imagined it as the perfect spot for a summer cottage. What the retired contractor ended up building—a 5,000-square-foot dwelling based on sketches by Frank Lloyd Wright—is a structure that some scholars have already likened to “Fallingwater.”

Massaro discovered the sketches in a drawer when he bought the property in 1991 and became determined to bring them to life.

In keeping with Wright's legendary aesthetic, the house is a marriage of natural and manmade forms. Pre-existing rock formations on the site serve as interior and exterior walls. Other hallmarks include exposed “rubblestone” footers, embedded with native granite, and a 27-foot, cantilevered concrete deck that juts out over the water. This design coup required city council easements on the normal 100-foot lakefront setback requirements in the building code.

Transporting the 150 tons of concrete needed for floors, ceilings, and walls onto the island was no easy task. In winter, Massaro waited for the lake to freeze over and used gator vehicles to drag raw materials across the ice from the mainland.

Some critics have asserted that, because the house was built based on sketches and not actual blueprints, it cannot be considered a legitimate Frank Lloyd Wright creation. Massaro asserts that the execution is true to form, save a few minor adjustments. “The entire house, all the way down to the furniture layout, has been built to his specifications,” he says. “The only thing we changed was the thickness of the walls for energy efficiency. In 20 years, people will look at this house and say that it's unmistakably a Frank Lloyd Wright house. But to be honest, I don't care what they call it. I'm calling it my home.”