I am attempting to plan a timber framed cabin (small, 16x24) and want to use posts anchored to concrete footings. I was thinking of using 6x6 posts (thoughts welcome), and because they’re exposed to the elements in north Florida, getting commercially pressure treated posts. I’d like to use as much of my own lumber as possible, though, partly because I have a sawmill and unlimited supply of good quality southern yellow pine.
So my question is: is it safe/advisable to use commercial pressure treated lumber for the lower portion of the posts, and vertically join my own lumber to make the remainder of the post’s height? Given the size of the cabin and that it’s in Florida where it may well face hurricane force winds more than once, I am concerned about tipping if there’s failure at that joint. Any thoughts or guidelines on this? I have seen posts vertically joined before, but I’m skeptical. I’m also wondering about the effect on the integrity of the joint as my lumber dries around a joint with already dried lumber.
I think the first important question would be how tall you plan to make the floor framing off the ground. The taller, the more stress on any post joints there will be. If more than inches, in hurricane country I would include diagonal braces in both directions from near base of posts to floor framing.
Timber framing restoration often uses scarf joints to replace rotted portions of old posts and beams. Medieval builders also used scarf joints to connect beams when they needed to be longer than available material. You can find plenty of directions and videos online. This video shows a very strong though rather complex version: