Hi Mike,

I now understand what you are saying - its just that you previously used the word "top" when what you really meant was the interface between post and tie (no need for a sketch).

Regards

Ken Hume

So, I explored with Sketchup what you two are talking about I think...

In the image below, would the weak point (shear) be at the corner of the diminished housing? That's what its saying to me. If that is the point, would a bore at the corner alleviating the corner help. Sorta of like a master that bored at the birdsmouth of a rafter. Also, I think what Mike might be referring to is the fact that you have a tenon on the top of the post right above a mortise for the tie. Whole lot of post gone with that. Maybe just cut the middle of the tie out and lap on both sides around the post...




I've always wanted to take a long through tenon and make and additional joint. In the picture above the tie extends through to the prafter and is keyed with a half circle cylinder. Would this help?


P.S. this is just for fun. I like to design stuff just to file away and try and learn from you all.

P.P.S I often wonder at what point the powers that be, just look at something like this and say, "Whoa, too many variables, lets just put some metal in there!". But thats not as much fun!

Mo, you got it. You've removed material for a through mortise, just where you want there to be strength in the post, and I'm assuming that directly above the mortise you've got a tenon. Because this is a truss, the forces heading down and out (from the rafter) want to lever the top of that post off... the larger the space between the rafter and tie, the larger the forces - and the less wood you have to work with. So its a balancing act. The post can fail at the peg holes, at the bottom of the housing, or if a check develops.

Now, you may have enough meat up there to do what you want - snow loads / wind loads / etc. and size of material vs. span may allow it to work - but I like your other solution better - of resolving the truss loads within the rafter / tie connection, and then letting that resolve gravity loads down onto the post. (then we load it up with wind... and it can get interesting again...)