A cascade unit for a heating system with two or more heating boilers, in particular condensing boilers, with a hydraulic shunt which is connected on the one hand with the inlet flows and return flows of all heating boilers and on the other hand with at least one heating circuit inlet flow and heating circuit return flow each, with the cascade unit furthermore comprising one each of the essentially horizontally extending boiler inlet flow header and boiler return flow manifold, the header and the manifold being connected with the hydraulic shunt, and the header and the manifold each being designed with prepared connecting nozzles fittingly placed for a group of two or more heating boilers for the connection of the heating boiler inlet flows and the heating boiler return flows. The cascade unit forms at least one self-supporting support frame on which at least one of the heating boilers is mountable.