Abstract: A building element comprises a topless and bottomless box, preferably manufactured in two halves which are joined together about the vertical diagonal. The top or bottom of the box includes a channel formation which engages the periphery of an adjacent element when stacked therewith. The elements may be stacked to overlap two similar elements located below it and once electrical, water and other service conduits have been placed in position, a concrete mixture or mud or the like is used to fill the boxes. This results in a sturdy structure that is inexpensive and which requires no maintenance or finishing.