Abstract: A precast, concrete building unit which is especially adaptable as a target house formed from concrete pour comprising a horizontal floor adaptable for placement on a subgrade, and vertical walls extending upright from the perimeter of the floor and precast integrally therewith. One or more inserts is imbedded in the concrete pour in the marginal walls of at least two of the opposed, vertical walls, and is adaptable for accepting a removable fastening element for releasable engagement with the embedded insert to facilitate lifting and handling. At least one recess is formed in the marginal walls of at least two opposed vertical walls. A roof is precast as a separate unit from concrete pour, and is provided with a downwardly depending fastening element for registry with the recesses as the roof is positioned over the walls so as to join or attach the roof with the walls to form an integral building unit.