Abstract: A moulding apparatus is used to form building blocks. The apparatus includes a plurality of vertical formboards in a pair of opposed rows, each formboard being connected to an adjacent formboard by clamps and spaced apart from opposed formboard by one of a plurality of partitions, each partition being attached to both the opposed rows thereby spacing the opposed rows apart and forming a mould between a pair of adjacent partitions and a pair of opposed formboards. The partitioning apparatus is useable to cast blocks in a course by filling the moulds with a hardenable material, the partitioning apparatus being positionable above the previously moulded course of blocks, with the lower edges of the formboards overhanging the previously moulded course of blocks, wherein apparatus further includes an insulation insert which is adapted to be formed into said blocks in a course such that a wall formed by the multiple courses of blocks is continuous.