An extension spring overhead door system (10) in which the spring (22) may be quickly and easily placed in tension with the door (21) in a closed position. A spring tensioning device (30, 140) is provided which eliminates the need for multiple installers to lift the full weight of the door (21) and then clamp or otherwise prop the door (21) in an open position. An extension spring containment tube (84) is also provided which surrounds the entire periphery of the spring (22) to fully contain the entire length of the extension spring (22). A second embodiment of the spring tensioning device (140) allows mounting of device (140) on either side of the door (21) while retaining easy access.