Abstract: A flooring system as disclosed which includes a substructure placed on an earth surface, which supports a floor structure. The substructure is composed of a plurality of longitudinally-extending I-beams interconnected by longitudinally-extending styrofoam blocks. A floor structure is connected to the substructure, the floor structure including flooring pieces having a long side and a short side. The flooring pieces are connected to the substructure so that the long sides extend transversely to the length of the I-beams. In an alternative embodiment, the I-beams include a support and location leg for connecting the styrofoam blocks. According to a method of the invention, the substructure and floor structure are interlocked by the criss-cross pattern described.