The science and engineering of the Manhattan Project was mind-bogglingly complex, but the endeavor was made even more difficult by the logistics of accommodating the tens of thousands of workers needed to produce the world’s first atomic weapons. Part of the solution included building thousands of homes like the B-1 Flat Top in Oak Ridge, Tennessee, a secret city that didn’t exist until 1942, and had to remain entirely unknown to the outside world.

Time was of the essence during World War II, and the Manhattan Project facilities needed to be constructed quickly. The Tennessee Valley Authority provided a solution with its Flat Top prefab homes, which could be easily transported and assembled almost like Legos. Each modular configuration was identified by a letter (A-F) and the B-1 design was 576 square feet, featuring two bedrooms, one bath, kitchen, and living room. More than 1,600 B-1 homes were built at a cost of $3,500 each. They were made out of Cemestos, a material combining the charm of cement and the salubrious character of asbestos.

The architectural firm Skidmore, Owings, and Merrill (of Sears Tower and Burj Khalifa fame) originally designed these fab prefabs, and were also charged with planning the Oak Ridge development. Of course, being a top secret project, they had to work with precious few details and were reportedly given only four days to submit the plan.  While much of the original Oak Ridge facility has been demolished, including the uranium processing plant that was the largest building in the world at the time, a few Flat Tops are still around, and the American Museum of Science and Energy has displayed a B-1 since 2008.

While the Flat Top inspires nostalgia, a short distance away on the campus of the Oak Ridge National Laboratory is an exemplar of high-tech modular home design that may portend the future. Adjacent to the Manhattan Project’s X-10 graphite reactor is a prefab home made entirely by a 3D printer. Companies all over the world are experimenting with 3D-printed homes, and in July, 2018, in Nantes, France, a family became the first to live in one. Reportedly, such homes are significantly cheaper to build, more durable, more efficient, and provide greater flexibility in design than traditional materials.