PURPOSE: To enhance the working effectiveness by providing a band-shaped mild steel plate with parts mating with an outer form, heat insulating material, concrete, inner form, and exterior material mounting frame, and forming an upward facing and a downward facing detent piece in each of these parts.

CONSTITUTION: A band-shaped mild steel plate transversely stretching to the left and right in a plane is equipped with parts which are mating with an outer form 2, a heat insulating material 3 positioned inside of the outer form 2, concrete 4, inner form 5, and an exterior material mounting frame 6. An upward facing and a downward facing detent piece are formed in each of these parts. The undermost positioned ones of the outer and inner forms are connected in the longitudinal direction, and the insulating material 3 is put alongside the inner surface of the outer form 2, and a separator 1 for construction works is set over the oversurfaces of the forms 2, 5. Further the downward facing detent pieces are detained with the upper edges of the forms 2, 5 and heat insulating material 3 and secured. The upward facing detent pieces of the separator 1 are detained and coupled with the over-part.