The present subject matter relates to systems, devices, and methods for mounting one or more lightweight architectural masonry units to a building support structure. An elongated track includes a web and opposed edge portions that form a pair of slide channels, the elongated track being configured to be mounted to the building support structure. A connecting member includes a base portion configured to retain the connecting member to the channels but is movable within the channels along the track, and a flange portion is configured to connect to a first lightweight architectural masonry unit of the one or more lightweight architectural masonry units. A fixation member includes a first end configured to connect to the elongated track and a second end configured to connect to the lightweight architectural masonry unit, the fixation member being configured to retain the first lightweight architectural masonry unit in place relative to the elongated track.