Completely understood! To be fair, no aspects of the math intimidate me, I'm just partly being lazy and partly uncertain about the different loading scenarios because I haven't had time to read up on them yet and time is getting short! Good to see confirmation my understanding of the concepts and principles are sound though!
I figured you could muddle through the math...but...like the rest of us, its just nice to "bounce concepts" of others. I just try to always plug in the disclaimer...just in case someone is trying to DIYer a frame over their heads.
Thanks for understanding...
So a few more details. We are doing a rubble trench scenario with short stem wall, but also stem walls running across the building under the bents upon which another 8x8 "sill" will sit. Since the bents are 12' spacing and the building is 24' wide, the interior space that is to be filled with the raised wooden floor is 24x12'. So joists going across the gap the shortest way are 12' long and will join with 8x8s that sit on concrete. Maybe you figured that out, but I just wanted to make sure!
That sounds like a very solid foundation...:) All we use is gravel trench and stone most often when we can get away with it. The trend today is to "throw" concrete at everything and think that is better. I always get a kick out of folks that don't think stone is stable enough...Often while they are standing inside a vintage timber frame that has been sitting on stone for a few centuries.
Your foundation (assuming the concrete is of good quality) should be around for at least that long...
Absolutely. This is why I'd planned on a fully housed dovetail.
Excellent...and to be clear...this means the entire end of the joist is housed into the 8x8. I do like Timbeal's suggestion "tusk" or "soffit" tenons. "Overlap" where the heel of the joist is house and the rest extends over the sill is also excellent. This would save you a great deal of joinery cutting...actually be stronger than the dove tail and would only ad at most 2" in elevation gain in one of the possible renditions.
Wondering about the legendary strength of my full 1" T&G white oak though and how much ply material would be required in concert with this? Would love to have plank underlay, but didn't have time to saw the material.
Hmmm....Well, it all depends on the joist spacing...etc. You will need a minimum of 2" for the kind of loads you are possibly subjecting that floor to...So...it all depends on the final configuration chosen.
Alternatively, what if I made a slightly wider stem wall such that wider and deeper joists could rest on the concrete itself with no housing in the sills. Could even consider 8x8 joists with dovetails cut in the ends to tie everything together but a housing would be exchanged for a good bearing surface on the wider concrete. I could cut some more joists, and save the 6x6 for other projects. I'm cutting it tight already for height on on the first floor, and already have the posts cut so I can't really put joists on top of the sills.
In general Brent...it will be your call. I am not fond of "dovetail joints" in general and the only ones I do like or have ever employed in a frame work in concert with other tying members and are only executed in the "Asian moralities" (i.e. Japanese - Korean forms) not European configurations. Most of the contemporary forms of this joint I have had the opportunity to go back and look at...well...not impressed with how they age.
Technically you could just set down a simple very rot resistant 2x plate (wood does not like sitting on OPC) and have the joist simply rest on the OPC stem wall with a "header sill" let into the bottom of the posts. this is more than strong enough and is the fastest foundation type we do on simple sheds, barns, garages, etc..
Good luck, and keep us up to date...Can't wait to see photos.