PURPOSE: To reduce the thickness of an underground outer wall as well as to raise the water-stopping property of the wall by a method in which steel plates are set between an underground continuous wall and an underground outer wall, and connectors are projectionally provided on both sides of the steel plates and buried in the continuous wall and the outer wall.
CONSTITUTION: A steel plate 4 with many studs 41 on its one side is penetrated into an excavated trench A for underground continuous wall, and a reinforcing bar cage 5 is set in the trench A. Concrete is placed into the trench A to construct an underground continuous wall 1. The inside of the wall 1 is excavated for a space for a building, and a formwork B for underground outer wall is temporarily set by welding many studs 41 to the other side of the plate 4. Reinforcing bars 6 are arranged in the formwork B and concrete is placed to construct an underground outer wall 2. Interference with the reinforcing bars 6 of the wall 2 can be eliminated, and the thickness of the wall 2 can be reduced. Also, by applying joint treatment for the steel plate, highly reliable water-stop layer can be formed.