When you have two beams connecting into one post at the same height, you need to get creative in cutting the joints. The goal here is to make a secure connection without taking too much meat and strength out of the post. In this detail we show you how to accomplish that with an Offset Mortise and Tenon.
We have shown you in the past how to secure two beams to a post with Spline Joinery, where a piece of hardwood is inserted into the post and into grooves cut into the beams. And that is one solution.
With an offset mortise and tenon as is shown here, the post has two mortises cut into it. Each one is set towards the side of the post so that they bypass each other, and neither one goes all the way through the post. This leaves plenty of "meat" in the remaining post. The beams have tenons that are offset to the same dimensions as the mortises, making for a nice snug connection when all is assembled and secured with hardwood pegs.
Another cool thing about this joint is that it allows the use of one set of pegs to join two beams, occurring at the same elevation, into a post.
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