Shear with notching. Why 6x8 joists on the flat??? The 1 and only Ed Levin writes: "It is apparent that the wider the timber, the deeper the notch that may be taken out. This sheds some light on the illogical use of square-section joists and beams in traditional structures where it appears that narrow and deep pieces would have served better structurally... It is often the case in timber framing that when a particular member seems poorly designed in structural terms, it makes perfect sense when the demands of joinery are considered." And it looks elegent too!!