Apparatus for spraying a building mixture comprising a nozzle holder (2), which holds a discharge nozzle (4), a mouthpiece main body (6), and a hose (18). A protection ring (10') is situated in a recess (7) and held in the recess (7) by a flange (21) of the nozzle (4) and an O-ring (22). The ring (10') has a number of holes (12') distributed around its circumference. The body (6) has multiple liquid inlets (16') distributed around its circumference and provided by high pressure liquid jet nozzles (24) inserted into respective bores in the body (6). The nozzles (24) are connected to a high pressure liquid supply system which allows a constant supply of liquid of the correct pressure. The nozzles (24) are fed with a liquid at a pressure which is sufficient to disrupt the dry components of the mixture and wet them thoroughly just before the mixture thereby produced is ejected from the nozzle (4).