An anchoring system for anchoring curtainwall units may include an anchor base structure to be attached to the floor slab, a vertical anchor structure and a horizontal anchor structure. The vertical anchor structure may be connected to a lower portion of the upper row curtainwall unit and bear a load of the upper row curtainwall unit on the anchor base structure, thereby fixing a distance between the floor slab and the lower portion of the upper row curtainwall unit while allowing horizontal motion. The horizontal anchor structure may be configured to be connected to an upper portion of the lower row curtainwall unit, and to use the anchor base structure to secure the upper portion of the lower row curtainwall unit against horizontal motion while allowing vertical motion.