Abstract: An isosceles joist structural member comprising two half-joists, each half-joist comprising a pair of elongated, substantially rectangular flanges, each having a surface and a longitudinally extended groove along the diagonal of the flange, and a web disposed between the flanges, the edges are adhesively fastened within the respective continuous grooves. A joint formed into the flange at the corner, on the flange diagonal, the widest part of the flange, cooperates to make the strongest joint in the member. Two individual joists connected together forms an isosceles triangle section, and repeats connecting top to top and bottom to bottom or bottom to wall to form a roof or floor structure. Dimensional graded lumber, engineered laminated wood, or synthetic composite structural members may be used.