Abstract: A modular building structure includes a plurality of prefabricated structural panels disposed in side to side relation, the panels being joined in dovetail fashion with a tongue extending the edge of one panel being received in a groove extending along an edge of an adjacent panel, the mating inner surfaces of the tongue and the groove each having a semicircular indentation therein, the indentations being aligned with one another to form a generally cylindrical channel extending the length of the two adjacent panels in which is received a cylindrical connecting rod which connects the adjacent panels together side to side. The connecting rods are connected to the foundation and/or to the roof of the structure to thereby tie the roof and panels of the structure to the foundation.