Abstract: A moulding method utilizing apparatus for forming a monolithic reinforced concrete modular building structure comprising walls and floor with apertures therein for doors, windows and the like. The apparatus comprises separable mould components in the form of a floor, end walls, side walls and a core moveable into cooperation with each other and a wheeled pallet to define a moulding cavity for forming the module, and out of cooperation to leave the formed module free for withdrawal on the pallet from the apparatus. The moulding apparatus is controllably connected to a source of pressurized wet concrete for filling the mould and is enclosed within an autoclave for accelerating the initial curing process of the concrete in the mould by heating.