A manufacturing line for gypsum boards includes a conveyor for moving gypsum boards in a line; a spray arm having a pivot at one end thereof for supporting the spray arm in a pivotable manner; a base frame mounted adjacent the conveyor; a support for the pivot mounted on the base frame so that the spray arm can be pivoted from an operative position wherein the spray arm extends over the conveyor to an inoperative position; a plurality of spray nozzles arranged on the spray arm for spraying a coating on gypsum boards on the conveyor; and a pump system on the frame to deliver the coating to the plurality of spray nozzles.