Abstract: A cavity wall spacer, building structure, and method are disclosed. The cavity wall spacer determines a separation of building elements of two leaves of a wall. The cavity wall spacer comprises: a support body; and a plurality of spaced projections upstanding from the support body and operable to extend across a cavity between the leaves, each projection having a recessed channel operable to inhibit transfer of moisture from one end of each projection to another. The recessed channel prevents the passage of moisture along the length of the projection to prevent moisture from traveling between the two leaves of the wall, and reduces the amount of moisture which drips into the cavity. The recessed channel has no external obstructions and thus allows significantly improved stacking density. The projections are less prone to any damage since there are no external protrusions.