A door system is provided for a door opening defined by a pair of vertically spaced jambs, a header positioned near the vertical extremity of the jambs, and a floor supporting the jambs. The door system includes a door, a plurality of track sections, the door being movable on the track sections, and a support system coupled to the door. Engagement of the support system when the door is in a closed position enables transfer of forces applied to the door at least to one of the header and the floor. One embodiment provides for automatic actuation of the support system by movement of a pivoting motor assembly to a closed position. Another embodiment provides for manual actuation of the support system.