Timber frame pole barn

[Bumper1990]

Hello, got a question for everybody. Im looking at building a 25x30 pole barn leanto i have 5.5 acres with trees and a chainsaw mill. Problem is all my trees are hickory, redoak, chestnutoak, and maple. So im having a sawmill cut my posts out of white oak since it will be in contact with the ground. My question for you guys is what should i put on the end? Tar? Heard of soaking them in motor oil? My next question is will my timber be fine for the rest of the structure? It will be under roof and metal siding so it should never get "wet" but how well will hickory hold up in that application? Would thompson water sealer help to spar the whole inside once and awhile or is that unnecessary? Am i ok with my wood choices? Local saw mill didnt have cedar. And no nonlocal had it either. All posts will be 6x6 and beams will be 6x6. Any advice,tip,help wouldnbe greatly appreciated thank you!

[Sedgehammer]

I'd never put any unpressure treated wood in the ground no matter how cheap the wood was sourced. Ever. Never.

[Brad_bb]

While I prefer not to put wood in the ground, I have repaired similarly built polebarns on our farm using Post Protectors.  A plastic sleeve that slides over the bottom of the post and sticks out of the ground at least a foot.  Only can be used when post is inside the building so rain can't run down inside the sleeve.  
https://www.postprotector.com/

[Don P]

All of those are subject to powderpost beetles. I would give everything a good soaking with a borate solution. If its all sided there's the bracing for the building, I'd pour concrete 8" above grade and anchor the posts on it

[hedgerow]

Take a look at permacolumn.com. We have been using these on pole sheds that the treated post have rotten off. If I build another pole shed it will have them. 

[PoginyHill]

If concrete is installed where the ground freezes, a tapered column is best. Can probably find local pre-cast products. I've used plastic footubes. Work well, just a little pricey. https://foottube.com

[Sedgehammer]

If concrete is installed where the ground freezes, a tapered column is best. Can probably find local pre-cast products. I've used plastic footubes. Work well, just a little pricey. The Footing Tube ? Shift Happens

Tapered.....
I can see the reasoning behind it.