Abstract: A U-shaped, half-room precast concrete building unit is molded in an open box-like framework having four L-shaped corner assemblies, facing pairs of horizontal legs of which are respectively joined by laterally-extending telescoping spacers, and facing pairs of vertical legs of which are respectively each joined by two laterally-spaced longitudinally-extending plates. Inserts having alternating voids and blocks are placed longitudinally between the vertical leg pairs to form complementary block and void patterns on the molded unit juncture edges. Retainers having projections are placed over the top edges of the plates to form complementary tongue and groove portions. Relative dimensions of the molded unit are selectable through adjustment of the relative positionings of the corner assemblies.

Abstract: A precast concrete building unit of half-room configuration with a floor or ceiling defining web portion and opposite half-wall defining flange portions is cast by pouring concrete over steel latticework in an inverted U-shaped cavity of a wheeled mold form which has hinged sidewall plates, removable pin mounted or hinged end plates, and a width variable segmented top plate. Matching ridge and depression insert elements placed in the mold serve to form the bases of the flanges with mating tongue and groove shear keys when the units are brought into flange-to-flange upright/inverted unit pairs to form whole rooms. Staggered blocks mounted on the top edges of the top plates project into the mold to form interlocking bearing surfaces for mating diagonally positioned web-to-web upright/inverted unit pairs. Units formed in the same mold can be used for rooms, columns, shear walls, retaining walls, elevator shafts, stairwells, girders and pedestrian bridges.