Continious length post on a tall frame?

I've seem some timberframes that are 3 stories tall. Do they all use continious length posts, or is it possible that they build a frame on a frame? If so, how do they joint the posts of one frame to another? I hope you are following what I am asking. I have a frame design in mind, and have some nice 12 foot timbers that I could use as posts, however the frame I want to build needs to be taller than that. I don't want to scarf posts, but was wondering if it was normal practice to build a frame on top of a frame? If so, how are they joined? Would it be like the top of the 1st frame acts like the sills and the 2nd frame fits into mortises? I'm just hoping to incorporate these hardwoodposts I have. Thanks, Brad

I was thinking about this more last night and realized that I can get the extra Height I need by using a concrete footer wall or individual post footings. I can cover them in ledge stone or wood. It's still a question I'd like to hear an answer to though.

Brad

I do not believe your question can be answered. I would be real wary of an answer if you got one. You can not take such details out of the context of the strucutre and applied loads. I recomend you have your plans approved by a qualified engineer before moving forward. I believe this will save you lots of potential heartache.

It seems to me that if your frame below is stable and you connect the frame above with stability.......

Yeah that's ok, it was just a general question. I'm just toying with some ideas and was asking about what has been done in practice, not trying to lock down a specific design yet. When I do get down to finalizing my design, I will do all the calcs (I'm a mechanical engineer), and then I will have it all checked by a licensed engineer in my state (who has TF experience).

Brad,

I've seen pictures of some old frames in Germany that were 4 and 5 stories tall that were built with single story posts. I don't know how they were joined. I would guess just mortise and tenons.

But with green wood you have to watch out for the cumulative shrinkage of all the plates/sills. If you have a post going up to a 10" plate and another on that going up to a 10" plate and a third going up to a 10" plate, you have 30" of wood that will shrink a lot -- maybe 2" (I don't have my calculator and formulas in front of me).

that really gets to be a problem when you have continuous wall posts and an interrupted ridge post. When the beam that interrupts the ridge post shrinks, the ridge drops.

gh

I know a lot of frames made with single story posts often have a jetty at each floor. I don't know if that is for the sake of the short timbers available, or to gain a little floor space as well.


Dave

Ok, what's a jetty?

where an upper story overhangs the lower story

Shrinkage can be a challenge, we stack post on post with timbers attached to sides of posts to reduce vertical shrinkage. Also, if the posts are shorter than the beams you can create sockets to drop the post on the next level into. Non-traditionalists can save the client a lot of money by implementing steel strapping, or internal steel fins bolted and counter sunk, holes filled with short pegs. One very important consideration is that each level be stable in and of its own, without relying on the others. Also, it is very helpful if the there is a complete floor system at each level that can function as a horizontal diaphragm to increase stiffness. It is very important that bracing be truly structural and not decorative, in that it be housed and not simply a tenon, and remember that braces do their work only in compression. For the truly challenging frames there are external solutions that can be applied to the frame under the panels or even within the panels. But as has been pointed out, a qualified, experienced timber frame structural engineer is absolutely essential.