Light weight fiber-reinforced polymeric (FRP) structural building panels and panel assemblies, sized and configured for construction of non-portable wall structures permanently fixed to the ground. Fibers in the panel are typically oriented within 15 degrees of a top-to-bottom, e.g. axial, direction in the panel providing, in part, enhanced top-to-bottom crush strength of a panel/wall. The panels typically have a bias to deflect toward the surface of the panel which faces outwardly of the building, toward the backfill soil which faces the panel on the outside the building. Panels of the invention typically have mass of no more than 18 pounds per foot height per linear foot length of the building panel, and vertical crush resistance capacity of at least 2000 pounds per linear foot length of the building panel, using a safety factor of 3.