Abstract: Apparatus for constructing modular buildings in which a reuseable framing structure is expanded to a shape desired of a building, building material is removably attached to the framing structure, fluent concrete is introduced to the building material, the framing structure is retracted with the building and removed. The framing structure has means for expanding its height and width. It also has means for changing the slope of its roof portion as well as changing the angles of its sides. Thus, many different shaped building can be constructed with the same framing structure.