Abstract: A building foundation wall is assembled from a plurality of rectangular prefabricated wall panel sections constructed of preservative treated lumber. The prefabricated sections are of standardized configurations adapted when disposed in end to end abutment to be substantially self aligning with each other, the standardized configurations including first and second configurations adapted to mate with each other to form a corner of the wall and other configurations adapted to abut each other in a tongue and groove relationship. All panels have an internal frame constructed with spaced vertical studs extending between horizontal top and bottom frame members and inner and outer side panels of plywood nailed to opposite sides of the internal frame. The upper edges of the side panels project above the top frame member of each section to define a lengthwise recess and a coupling board snugly received in the recesses of two abutted panel sections aligns the panel sections and secured them to each other.