Abstract: A lightweight, prefabricated building structure is assembled from panels having positive attachment means for attaching each of the panels to a suitable foundation. Each of the panels has friction lock means for interlocking one to another. Roof panels are provided which are joinable to the edge on the upper surface of the panels by the same type of friction lock means. Panels consisting of polyurethane can be easily shipped to a building site and erected with a minimum of cost and manual labor.