pressure treated wood

[xlogger]

I've started cutting material for the shed that collapsed with the snow load before Christmas. It was 24x40. I'm buying steel trusts and setting them on 6x6's concreted in ground. The way pressure treated is now does not hold up like before. I was wondering if I burnt the poles that was underground would they last or hold up longer?

[Don P]

The charcoal part will, the wood, not really. If you get the building supply to order foundation grade treated, I believe the classification is UC4B, use category 4B, it will be well treated. Thank Lowes and the others for stocking non ground contact treated .

[nativewolf]

Yes/no.  Use some locust/osage post or buy marine grade treated lumber.  Burnt wood rots and you open up the end of the log to rot.  The ends of treated wood are the weakness, you can paint extra preservatives on it but that open pore structure is where it will weaken first.  Any knicks, cuts, flaws, etc that happen during handling are another weak point.  Marine grade pretty much will trump all of that.  Older preservatives were crappy products anyway, they leached pretty nasty metals right into the ground. 

[Don P]

A buried end does not rot, no oxygen down there. Take a look at fenceposts, they rot right in the ground line area where the biology is going on, the bottom is as good as the day you buried it. That said I put the uncut end of a post down in the bottom of the hole. I figure that same porous end sucked up more of the good stuff. Marine grade is the bomb if you can get it, they just look at me funny up here when I mention it.

Concrete in the bottom of the hole that the post sits on spreads out the load over a wide footprint. Pretty often when I get called in on a barn or outbuilding that has sort of blended into the rolling landscape, the poles were simply buried on dirt or had a collar of concrete that they slipped down through. They need a snowshoe to spread the load out.