A new model for describing electrochemical aggregation and growth via a layer-by-layer mode is described, where there are competing phases. The earlier version of "the cascade approach" is generalized to accommodate two components, i.e. phases A and B, growing with their own mechanisms of nucleation and accretion. The overlap corrections under such competing situations are made through an extended Avrami ansatz. Several possible outcomes are indicated including the exact predictions of the steady state limit for the current, exhibiting different Tafel regimes, with slopes determined by the relative importance of the parameters characterizing the A-on-A, A-on-B, B-on-A and B-on-B transitions. Special cases to reflect partial and total blocking of the growth of one by the other are also discussed.