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Thread: Best way to secure a round post on concrete base

  1. #1
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    Default Best way to secure a round post on concrete base

    I'm trying to set a round post (a log) on a concrete base (sonotube) for a small pole barn-type structure. Concrete to ground level and post above ground. The posts will average around 8 inches at the base. I'm having a hard time figuring out how to secure the posts against lateral and lifting forces.

    The best I can come up with is a bolt out of the concrete and a "U" shaped iron strap.

    Other than just burying the post, is there an easier/better way to do this?

    Thanks

    Tom

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    Default Re: Best way to secure a round post on concrete base

    In fact, if you can saw a penciled line, apply glue, drive nails, and bring a modest measure of patience to the task, you can build and launch a smart and able craft in as few as 40 work hours. You need not be driven by lack of tools, materials, skills, or time to abandon in frustration a project you conceived in a spirit of pleasurable anticipation.

    -Dynamite Payson

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    Default Re: Best way to secure a round post on concrete base

    Thanks. I should have said 8 inches diameter at the base. So the standard post base will not work.

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    Default Re: Best way to secure a round post on concrete base

    Quote Originally Posted by bluedog225 View Post
    Thanks. I should have said 8 inches diameter at the base.
    I'd cut two opposing sides square with a skil saw at the bottom, then use a standard two piece tie-down like switters posted. Failing that a I'd use a large section angle iron.

  5. #5
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    Default Re: Best way to secure a round post on concrete base

    Shave two sides of the bottom of the post, and use a normal post base.
    Last edited by Donn; 09-23-2010 at 04:48 PM. Reason: Paul beat me.

  6. #6
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    Default Re: Best way to secure a round post on concrete base

    Hmmm... here's an idea. Use a standard U bracket, secured to the concrete base with an expansion bolt. Drill a clearance hole in the bottom of the post, in the center, which clears the head of the expansion bolt. Cut two slots in the bottom of the post, the same dimension apart as the ears of the u-bracket.... and then bolt through the post, and through the ears of the u-bracket, to the opposite side. I wouldn't want to shave down the base of the post to the dimensions of the u-bracket, because you lose strength at the bottom... doing it my way, the entire area of the post can bear on the concrete, and the bracket keeps it in place.
    "Opinions you like, presented to you and others who share your opinions, from someone whose opinion you already know"
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  7. #7
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    Default Re: Best way to secure a round post on concrete base

    The point is that the post does not bear on the concrete, trapping moisture and rotting out.
    In fact, if you can saw a penciled line, apply glue, drive nails, and bring a modest measure of patience to the task, you can build and launch a smart and able craft in as few as 40 work hours. You need not be driven by lack of tools, materials, skills, or time to abandon in frustration a project you conceived in a spirit of pleasurable anticipation.

    -Dynamite Payson

  8. #8
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    Default Re: Best way to secure a round post on concrete base

    I'd run 3 or 4 long galvanized lag bolts into the base of the post, protruding 6 inches or so. Place large washers on each. When you're setting the post, block it up so there's an inch or so above the concrete. This keeps the butt out of the water and will help the post last longer. It wouldn't hurt to paint some wood preservative on before setting the posts.
    -- Tom (boating blog)

  9. #9
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    Default Re: Best way to secure a round post on concrete base

    A knife hanger or strap.

    Hopefully you haven't poured the concrete yet?

    A flat strap poured into the concrete , use a chain saw to cut a "scabbard " / plunge cut into the bottom of the post , thru bolt the post to the metal strap.

    I'll be doing some thing similar in the next few weeks, although the knife hanger / bracket I'll be using has a 7 3/4" square flat base and a 4" wide x 12" long strap off the top. It will be bolted down by boring 4 each 5/8" dia. holes into existing concrete with 1/2" SS threaded rod epoxied in to the bored holes.


    You might be able to do a similar thing althought with only a 8" concrete post base your bolts into the concrete would be a bit close to the edge of the concrete base.

  10. #10
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    Default Re: Best way to secure a round post on concrete base

    Or a Simpson type hardware made for this application,

    UB-WUB.jpg


    Other types found here: http://www.strongtie.com/products/ca...ost_bases.html


    The type that are poured in tend to have higher strength ratings for both uplift and lateral support.

    The Knife type hold downs we get made up to our spec's generally out of 316 SS.

  11. #11
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    Default Re: Best way to secure a round post on concrete base

    bottomless bucket with epoxy sand slurry - post in the bucket, bucket on the slab.

  12. #12
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    Default Re: Best way to secure a round post on concrete base

    Quote Originally Posted by tomlarkin View Post
    I'd run 3 or 4 long galvanized lag bolts into the base of the post, protruding 6 inches or so. Place large washers on each. When you're setting the post, block it up so there's an inch or so above the concrete. This keeps the butt out of the water and will help the post last longer. It wouldn't hurt to paint some wood preservative on before setting the posts.
    Thanks. Would I need to get the bolt heads pretty close to or tied to the rebar to keep them from pulling the top of the concrete peir off?

  13. #13
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    Default Re: Best way to secure a round post on concrete base

    Quote Originally Posted by Paul Girouard View Post
    Or a Simpson type hardware made for this application,

    UB-WUB.jpg


    Other types found here: http://www.strongtie.com/products/ca...ost_bases.html


    The type that are poured in tend to have higher strength ratings for both uplift and lateral support.

    The Knife type hold downs we get made up to our spec's generally out of 316 SS.
    Thanks. I didn't realize I could order them that large.

  14. #14
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    Default Re: Best way to secure a round post on concrete base

    IMO, the weakest mechanical connection would be lags running with the grain of the wood

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    Default Re: Best way to secure a round post on concrete base

    I'm going to assume that you haven't poured yet, Get some 1/2"X2" flat stock. Have them cut into 12" and 4" pieces and have the 4" piece welded on one end to make a "T". Blow a 1" hole on the top and set them into the concrete, plumb. Six inches above grade with a nice 1" hole. Drill out the bottom of the log with a 5/8 bit, make a mortise. Drill the one inch hole in the log and drive a broom stick through. You could use a dowel if you want

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    Default Re: Best way to secure a round post on concrete base

    Quote Originally Posted by bluedog225 View Post
    Thanks. Would I need to get the bolt heads pretty close to or tied to the rebar to keep them from pulling the top of the concrete peir off?
    As long as they protrude a few inches below the top of your rebar I think you'd be safe. I don't think you'll have room to get in there to tie them off.

    Donn, you're right that threads going with the grain aren't especially strong, but in this case, with enough thread, and 3 or 4 bolts, it should be more than strong enough. It would take a lot of lifting force to rip them out.
    -- Tom (boating blog)

  17. #17
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    Default Re: Best way to secure a round post on concrete base

    I got good results on previously poured concrete posts by hammer drilling a 1 1/2" hole in the concrete 12 inches deep, then drilling a 1/2" hole 24" up into the center of the log post. I then ground a bit of a bevel on the end of a 34" piece of hot dipped 5/8" threaded rod and sledge hammered 24" of it into the end of the log. After applying several coats of wood preservative to the end grain I filled the hole in the concrete 1/2 full of expanding grout and laid 2 layers of roll roofing on top and let the log and pin down onto that, turning the log a couple of times to seat it in any squeezed out grout. Bracing held the log plumb whilethe grout hardened, and excess roll roofing was trimmed later.

    If the bottom of the post is going to be anywhere near grade you should make sure to design in considerable overhang to the roof in order to keep the log end as dry as possible.

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