Abstract: A cardboard structural member for use in the construction of building panels and a method of making same. The structural cardboard member comprises an elongated hollow channel member of rectangular cross-section formed of corrugated cardboard sheeting. The channel member defines opposed parallel walls and is opened at its ends. One pair of parallel walls terminates short of the ends of the structural cardboard member to define a connecting channel across the ends for receiving a rigid structural member thereacross between two opposite walls when assembling the panels to construct a building structure. The method of assembly consists in glueing a plurality of these structural members side by side to form the panels.