I agree with Joel, as evidenced by my earlier opinions on this matter. Untreated wood should not come in contact with concrete whatsoever. Building Inspectors will not allow it. Also, burying a post in concrete creates an opportunity for concrete failure despite the longevity of the wood. Wood expands and contracts with moisture content. At some point there will be space for water and therefore concrete detoriation due to freeze/thaw cycles. The deeper the post is buried the more likely any flexure due to wind loads will incur significant pressure on the concrete at the surface due to the lever action of the bending in the post, which ultimately could cause spalling, especially if weakened from the freeze thaw cycle. Lastly I'm not sure that I have confidence in any product remaining water tight for the long term, and even if it does, there will be water inside the post due to absorption from the air that can only wick out through the exposed portion of the post, not to mention water that ultimately might make its way down the side of the post on the inside of the "post wrap". I am unfamiliar with any accepted practice allowing wood buried into concrete.

Paul brings up an excellent point about water being trapped in the wood when set in concrete. At the risk of encouraging this, I've read where IF you're going to do this, to have the bottom end of the post lower than the concrete to allow the water to drain. I'd venture a guess that some stone under the post would be a good idea.

Joel

Back to the solution by getting the concrete footers above grade. Cardboard forms (both cylindrical and pyramid style) are out there in the market place.

Since there's current activity on this, here's the solution we came up with for the original post:
We imbedded a 1/2 inch steel plate (8 inches x 48 inches - posts were 16x16) plate verticaly into a concrete pier, tied into the re-bar via holes in the plate. Concrete went from below frost line to ground level. As a platform for the post, we slid another piece of 1/2 inch plate (12 inches square)with a slit cut into it over the verticle steel. Each horizontal plate had four bolts to level it relative to the other posts and hold it approximately 3 inches above ground level. Once level, concrete was packed under to form a 3 inch pyramid capped with steel. A piece of EPDM rubber roofing topped this.
The post bottom was routed out so the bearing surface was up inside the post one inch. This provided a full drip edge around the perimeter. The slot in the post was plunge-cut freehand with a chainsaw. Bolt holes were drilled in the posts before raising, then through the steel plate once it was up. Bolts could have been countersunk and the holes plugged, but we knew a good blacksmith, so had some fancy bands made to go around the posts and cover the bolt heads.

Thanks Pete, for having the last reply on this (since you started this topic.) However, I am going ahead with the vycor wrap to prevent any concrete contact. This is the most economical/beneficial way to proceed.

Also, I want to point out that this is TREATED wood, .60 cca pine (most recommended for underground use,) structural 8x8 (nominal) treated pine that is going to support a widely used and recognized king post/strut truss design.

I realize that this forum is most familiar with the use of oak timber, thus untreated, and the only real test of a total design..........is time. I do not want to build a poor structure, however I feel that the comments presented are from professional viewpoint that doesn't represent any tolerance for change or ingenuity. Again, the only real test of a design is time.

My hope is that this simple structure will last for ages. Thank you all for your input.

Regards, Tim

Looks like we need a book on post bottom connections!

One I've used more than once is HDG "eye" bolts set in concrete wet (with nuts & washers) or dry with epoxy. Install a nut with a large square "washer" above it at about the desired height of the post bottom before you set the bolts. I like to leave some daylight under posts.

Next mortice the bottom of the posts for the eye bolts. Raise and adjust the "washers until the building is right and peg the posts through the "eye". Simple, but does require some care in layout. I would have to beleive a 1" dia. locust peg is pretty good for uplift too.

Rudy