A construction method of a fermenter, which has a fermenter cage and a fermenter shell made of metal, for use in a biogas plant, wherein the fermenter shell surrounds the fermenter cage making the fermenter shell gas-tight. The fermenter cage is formed by a plurality of cage rings, wherein each cage ring is supported on at least one cage-retaining device having at least one rolling device in such a way that the entire fermenter cage is rotatably supported about a longitudinal axis, wherein the fermenter cage is lined with a plurality of rows of shell plates by way of rotation about the longitudinal axis and the shell plates are permanently fastened to the inner surfaces of the plurality of cage rings and thus the fermenter shell is formed.
