Redwood posts

4 x 4 redwood posts are bolted to the straps in concrete piers.
When replacing the posts, how can I prevent the bottom of the posts from deteriorating/rotting?

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Keep them off concrete, for sure.
Greg

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And, treated lumber holds up somewhat better.

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Nothing will be perfect. Wood in the ground won't last forever. However, if the posts extend beyond (deeper than) the concrete into some gravel, the bottoms will drain and they won't rot so fast. About the worst thing you can do is put wood into concrete, without letting it stick through the concrete.

On Oct 16, 5:51 pm, " snipped-for-privacy@att.bizzzzzzzzzzzz"
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I believe the OP's situation is 4x4's on a pier block...like for a pier & post foundation, only wood / concrete contact, no penetration into or through the concrete here.

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They do make a metal post holder that keeps them off the ground. You put an anchor into the concrete, bolt the holder in place, then nail or screw the post through the flanges.
In any case, I'd put some Penofin oil on the post ends anyway. Should last decades like that.
http://www.homedepot.com/buy/simpson-strong-tie-z-max-4x4-uplift-post-base-abu44z.html
http://www.strongtie.com/products/connectors/AB-ABA-ABE-ABU.asp

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Ed, would creosote be better than the penofin oil to prevent wood rot in this situation?

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Doug-
Yes, creosote is a great wood preservative but...
http://www.epa.gov/pesticides/factsheets/chemicals/creosote_main.htm
synopsis: Creosote is a wood preservative used for commercial purposes only; it has no registered residential uses.
cheers Bob

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Thanks Bob. I guess I haven't kept up this stuff since my dad used it years ago.

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But copper naphanate is still available as a wood treatment & is available by the gallon at hardware stores. Pour it in a small diameter bucket and stand the 4x4 in it overnight to allow it to wick up. It'll turn your redwood green for a few weeks, then the sun will bleach it back natural.
Red

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It would probabaly be a lot beter. Only problem is where to get some of this stuff. I though the EPA or whatever outlawed it years ago.
Most everything that worked really has been outlawed.

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Make a block of 2x4 of old growth heartwood redwood or heavily treated wood (soaked in an appropriate wood preservative) as the piece beneath the end of the 4x4 and against the concrete.
Think of if as a chunk of mud sill. Transverse grain is much more resistant to moisture than end grain. End grain against concrete is bad design practice
If your new posts are not heartwood they're not going to be very resistant.
You could also soak (over night) the ends of the 4x4's in paint cans with a few inches an appropriate wood preservative.
What is your application? raised deck? post & pier foundation repair?
Ed-
I believe the OP is using a pre-made pier that includes the straps. The Simpson product you suggest could be "cut down" (strap portion removed) and the remainder used a giant galvanized spacer. :)

On 10/16/2012 6:06 PM, gary wrote:
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use steel posts

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pour copper green into a five gallon bucket, stick the posts into the bucket, let sit for one month.
And remember 'green side down'