when a building had 'jetties' or cantilevered overhangs on 2 sides, diagonal dragon beams joining main beams near the centre support the upper floor corner posts. There is a microcosm of timber frame construction here all at the one location. For comparison see also grander examples
http://www.pbase.com/crisscross/image/72308754
http://www.pbase.com/crisscross/image/74474585