A deck system includes plural deck units fastened together and carried directly by the framing system of a building directly or indirectly by frame elements that are themselves carried by the framing system. To relieve lateral forces on the deck system that exceed a pre-engineered level, these frame elements include a slidable support and slidable brackets both with slotted holes that permit controlled and limited movement of the deck system in two mutually orthogonal directions with respect to the framing system of the building. In addition, the individual deck units may move horizontally with respect to the each other and the framing system. Each decking unit may be connected to an adjacent decking unit using a slotted hole formed in one of its two side laps.