A method for manufacturing an innerspring unit comprising pocketed springs, the method comprising the steps of (a) providing an innerspring main body comprising a plurality of first strings of pocketed springs; and (b) attaching at least one second string (13c, 13d) of pocketed springs to a lateral surface of the innerspring main body, so that the at least one second string (13c, 13d) of pocketed springs extends in a longitudinal direction of the innerspring main body, wherein the springs of the at least one second string (13c, 13d) of pocketed springs have a spring characteristic or a spring geometry different from the springs of the plurality of first strings of the innerspring main body, the at least one second string (13c, 13d) of pocketed springs forming together with the innerspring main body the innerspring unit, wherein step (b) comprises compressing the springs of the at least one second string (13c, 13d) of pocketed springs prior to attaching the at least one second string (13c, 13d) of pocketed springs to the innerspring main body and allowing the compressed springs to expand after attaching the at least one second string (13c, 13d) of pocketed springs to the lateral surface of the innerspring main body, wherein the method is performed as a fully automated process by an innerspring unit assembly machine comprising a first station for providing the innerspring main body by carrying out step (a) and a second station for manufacturing the innerspring unit from the innerspring main body and the at least one second string (13c, 13d) of pocketed springs by carrying out step (b), and wherein the innerspring main body is transported from the first station to the second station using a conveyor device. (a) providing an innerspring main body comprising a plurality of first strings of pocketed springs; and (b) attaching at least one second string (13c, 13d) of pocketed springs to a lateral surface of the innerspring main body, so that the at least one second string (13c, 13d) of pocketed springs extends in a longitudinal direction of the innerspring main body, wherein the springs of the at least one second string (13c, 13d) of pocketed springs have a spring characteristic or a spring geometry different from the springs of the plurality of first strings of the innerspring main body, the at least one second string (13c, 13d) of pocketed springs forming together with the innerspring main body the innerspring unit, wherein step (b) comprises compressing the springs of the at least one second string (13c, 13d) of pocketed springs prior to attaching the at least one second string (13c, 13d) of pocketed springs to the innerspring main body and allowing the compressed springs to expand after attaching the at least one second string (13c, 13d) of pocketed springs to the lateral surface of the innerspring main body, wherein the method is performed as a fully automated process by an innerspring unit assembly machine comprising a first station for providing the innerspring main body by carrying out step (a) and a second station for manufacturing the innerspring unit from the innerspring main body and the at least one second string (13c, 13d) of pocketed springs by carrying out step (b), and wherein the innerspring main body is transported from the first station to the second station using a conveyor device.