The invention relates to a modular assembly that comprises at least two housing parts (1), in which in each case a circuit board (L) is received, at least one internal connecting means (17), one cover element and one closing element. Each housing part (1) is formed from a base plate (3), a rear wall (5) and side walls (4) that are connected to said rear wall. The housing parts (1) are stacked in such a manner that the side walls (4) combine to form a first (6) and a second complete side wall (7), and that the rear walls (5) combine to form a complete rear wall (8). At least two of the housing parts (1) are stacked in such a manner that the base plate (3) of the one housing part (1) is connected to the side walls (4) of the other housing part (1). The at least one internal connecting means (17) extends in a direction perpendicular to the base plates (3) and connects multiple circuit boards (L) by way of first connectors (18). The cover element lies on the side walls (4) of precisely one housing part (1). The closing element is attached to a front side on the housing parts (1), said front side lying opposite the complete rear wall (8).