I am planning to build a pole building to use as residence using 6″x8″ treated posts. The posts will sit on a 1 foot concrete pad 4 feet deep and get surrounded by concrete, probably with a sonotube. Is there any additional steps I can take to keep the posts from rotting? This is in Washington State and it is quite rainy where I am building.
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Yea, they not to have a foundation-grade level of preservative. For CCA, this was 0.6 psf; 'not sure what this is for the new preservatives.
Wood with this level simply does not rot. I have a 15-yr. old pole barn, and the posts show no signs of decay; even those exposed to moisture and manure very freequently.
The preservative level for the posts should be specified on the approved plans (which I assume you're using, since this a residence and not an outbuilding).
Nothing lasts forever, the figures I have seen give the typical service life of 0.60 pressure treated wood in damp conditions something on the order of 35 to 40 years.
http://www.conradfp.com/enviro.htm
Yeah, don't surround them with concrete. Concrete acts like a sponge holding moisture next to the wood. I would use <=3/4" crushed run gravel to backfill. It allows water to move away from the wood. Tamp down every 6" lift.
SamT
FWIW, all the barn contractors in this area backfill with concrete. Mostly I think because it's fast and foolproof - no careful tamping while backfilling. Just place 'n brace the poles, and call the ready-mix truck. Besides, assuming you have proper gutters, there should not be much moisture hitting the ground around the poles. And 0.6 psf PT wood isn't affected by moisture.
There also needs to be a concrete pad underneath each post, BTW.
Sometimes I put posts into concrete. When I do I make sure the top of the footer slopes away from the post a bit, and I wrap a band of copper around the post.
Seems to me that rot and mold need moisture and ozygen, only found up at the surface there. The oxidising copper kills all of it. Looks pretty nice too !
http://www.hpphoto.com/servlet/com.hp.HPGuestLogin?username=joe_wood&password=69805200