Will,
Thanks for the tip on the book. I'll call the museum ASAP.

I don't have my copy of Jack's book "Historic American Timber Joinery" with me right now, but I recall him describing this dropped tie to post joint as common and also likely to fail.

The GSL is 90 PSF in Allegan County though the further you get from Lake Michigan that will decrease. Most of the barns I have met in Michigan feature 2" mortise and tenon joinery. One of these two barns is all white oak and the other is mixed hardwood. The posts are 8x8.

The load is carried by the 2x rafters to a scarfed top plate thence to the posts. The tie beam is in both cases about 2 feet below the plate. The only resistance to outward thrust was the pegs holding the post and tie together.

In most cases around here barns have been given many layers of roofing to bear up in addition to the snow load and farmers are loath to spend on removal and reroofing. I am not surprised these joints are failing but sure would like to find a solution to their problem.

In that vein, is there a preference out there amongst framers? Wooden repairs, steel brackets, chains, cables, ropes? I imagine it would matter if the barn was to be reused as a barn vs converted to a residence. It would surely make me nervous to live in a structure bound by steel cable but I image the cows and chickens don't mind.

-Shawn