Setting Cedar Posts

sasso_999May 3, 2007

ok I know now that the way I should have done this was to set PT posts and wrap w/ cedar, but I already bought 4 12-foot 6x6 cedar posts for an arbor that I'm building. So I'm trying to figure out the best way to do this.

I have gotten a few tips that may help prevent rotting: 1) coat with tar and wrap with tar paper, 2) wrap the with copper, 3) Use a wood preservative (link below), 4) put gravel at the bottom to help with drainage

Can anyone speak to any of these tips, or does anyone have any other advice? The thing is here in Houston, TX the water line is about 2 feet down, so that's got me a little concerned, and makes me think gravel will not do anything. I have to admit I thought cedar was impervious to rotting before I started researching.

Thanks

Here is a link that might be useful: wood preservative

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sasso_999

Forgot to mention that I feel like I need to set the posts in concrete 30" down for stength, since I'm building a 70 sq ft arbor about 9 1/2 feet tall.

    Bookmark   May 3, 2007 at 11:54AM
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bindersbee

You're going to have problems with the posts at 33" down if the water table is 24" down. I don't really see how any of the above techniques can help given the water table. You might want to consider the FiberForce structural plastic lumber posts from Bedford Technologies. We used these on a local playground project (200 of them). They are VERY heavy and dense but also relatively immune to water problems. Here's a link to the website. It might be cost prohibitive but it would certainly be the ideal in your situation.

Here is a link that might be useful: Bedford Technologies

    Bookmark   May 5, 2007 at 8:30PM
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ron6519

Your dooming the project to premature failure with the current plan. Burying any wood in dirt is a bad idea. Set concrete sonotubes and standoffs and put the posts on them, off the ground. Integrate lateral bracing into the design for sideways forces. Wrap the bases with sacrificial moldings that will decay in a few years. If your going to paint the arbor, use the composite wood and your done.
Ron

    Bookmark   May 6, 2007 at 10:35AM
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deckman22

If you are not in a hurry then call a couple of welders & see if they can make you some custom post base. I use them on all free standing structures like pergolas/pavillions.

Have the welder make 12"x12"x1/4" plates that have 4" pieces of 1/2" rebar welded on the bottom sides, one on each corner. On the top have two plates 6"x12"x1/4" welded 6" apart @ 90 degrees from the 12x12 plate for the 6x6 post, centered of course. In each verticle plate have 3 - 3/4" holes drilled. You place the post base in the concrete right after you pour your footing. After you put thru-bolts in the 3 holes you don't even need to brace off the post to hold them level they hold so good. Make substantial footings, 24"x24" 6" above grade & 12" below grade w/1/2" rebar grid should work there.

Wrapping your post & burying them will surely make them rot in no time there in Houston, I don't care what you try to use to prevent it.

Simpson makes something similar, but it's made of thinner steel & don't hold as well. They have to be special ordered in most cases & cost just as much too.

Al

    Bookmark   May 7, 2007 at 12:39AM
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