A method for forming a hopper in a storage structure includes mounting a form to a storage structure which bounds a compartment. The form can be flexible or rigid. A layer of cementitious material is applied over an exterior surface of the form so as to produce a rigid side wall. The rigid side wall has an interior surface bounding a progressively constricting flow channel that communicates with the compartment of the storage structure. In one embodiment, the layer of cementitious material is applied by spraying.
