Batch building processes are common in many areas of material flow and production systems and of communication networks. This paper presents an analytic method to calculate the inter-departure time distribution and the waiting time distribution for batch building processes using discrete time analysis. The batch building process happens at so called collecting stations in the considered queueing network, at which the arriving customers are collected up to a defined capacity. The arrival is a batch arrival of stochastic size and is described by a generally identically distributed inter-arrival time. The presented method enables a performance evaluation of batch building processes in a stochastic environment.