Abstract: A method for building wall slabs (45) from building blocks (21), in particular for the partial prefabrication of buildings, is further developed, with the aim of further rationalisation and quality improvement, in that the building blocks (21) of each individual layer are first laid out in a row, taking into account possible mutual spacings, and then placed together in one movement with the upper side downwards. The associated device consists of a horizontally movable gantry framework, on which a turnover table (20) is provided which is attached winglike to a horizontal shaft (17) and has a clamping device (25,26) for a layer of building blocks (21), with the shaft (17) extending parallel to the wall slab (45), being accommodated, at its ends, in bearings which can be moved vertically, and having a drive for the swivelling movement through 180.degree.. The building blocks are laid onto the turnover table (20) at a convenient working height with a suitable crane.