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Thread: Attaching 4x4 posts to concrete

  1. #1

    Default Attaching 4x4 posts to concrete

    I am istalling a 6 ft., vinyl fence around my pool area. I am also pouring new concrete around much of the area, so I will be able to sink the majority of the post in the new concrete. There will be a few places where I'll have to mount the posts to the existing concrete. I was wandering if anyone had a good method of securing a 4x4 treated post to concrete. I will be putting a 4x4 vinyl sleeve over the 4x4 treated post. I am aware of the bracket that you fasten to the concrete, then to the post. Using that method concerns me about how stable the top of the post will be. Any ideas will be greatly appreciated. Thanks, your little buddy.

  2. #2

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    Check out this thread. I learned a lot from it:

    http://www.terrylove.com/forums/showthread.php?t=14808&

  3. #3
    In the Trades Bob NH's Avatar
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    Since you are covering the post with vinyl, you could weld 3.5" square x 1/8" wall steel tube to a base plate and bolt the base plate to the concrete with really good anchors. The steel tube is the same dimension as the 4x4 posts.

    You might be able to get less expensive pipe and put spacers on it to fill out to the 3.5" square dimension.

    If you have a very good concrete slab you can use a 6" square base plate and anchor it with a single 5/8" fastener in the center. You would need a long extension on the socket wrench and access down the length of the post. You will also need to shim and grout it carefully to get the post plumb.

    You will need to work out railing attachment details for the steel post but that shouldn't be a problem.

    It will be much stronger than any attachment you are likely to make for the wooden posts.

    Another solution would be to put steel or PT posts through the slab.

    Be aware that much of the available not-so-toxic treated wood now availavble is not treated for underground use.

  4. #4
    Architect Spaceman Spiff's Avatar
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    Look here...

    http://www.strongtie.com/products/ca...ost_bases.html

    I'd use the ABU or the EPB44T. I used the EPB44T and it allowed me to adjust the post to make all of them level, plus both of these have great uplift performance. (we routinely get 60 MPH winds here...) The ABU would be better for your application tho, I think.

    Finally, as Bob suggested, maybe you should look at a steel fence system or a hybrid with steel posts and vinyl rails. Steel posts bolted in 4 places (using a foot plate) would be the strongest...
    Spaceman Spiff aka Mike

  5. #5
    Plumber jimbo's Avatar
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    Frankly, I don't believe any of those Simpson products are adequate for a 6' fence post. They are for structure posts, and resist horizontal loads applied at the base. I do not think they are adequate for the leverage of a load applied at the top of a 6' post. The weakest link is actually the attachment of the post to the anchor.

  6. #6
    DIY scratch-pad engineer leejosepho's Avatar
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    Quote Originally Posted by Bob NH View Post
    Another solution would be to put steel or PT posts through the slab.
    That is what I would do: Cut a clean hole in the existing concrete and install those posts just like the rest of them.

  7. #7

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    I would find square tube steel stock or make one) and run the post into it about 8 inches, with a tight fit, maybe even sand the sides of the post a bit and use angle iron (from a bed frame) welded to form a lip to screw it to the concrete.

    Also, I know it isn't a common practice to place sand in the bottom of the hole when putting a pole in concrete, but I suggest 4-6 inches of sand at the bottom of the hole to prevent rot. Even the impregnated stuff rots when wet. The sand helps draw moisture away a LOT if you're in an area that gets a lot of moisture.

  8. #8
    DIY Hillbilly Southern Man's Avatar
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    The only way that you can use a Simpson post base is for a corner condition like this where the post is supported north-south and east-west by the railing. http://www.terrylove.com/forums/show...3&postcount=16

    If you have a straight run post on the concrete you'll need to do what either Jeremiahiii or leejosepho suggested.

  9. #9
    DIY Hillbilly Southern Man's Avatar
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    You could also use 4 of these on the post bottom, one on each side.



    They would be a special order item and can be finished in powder coat, gray primer or galvanized.

    http://www.strongtie.com/products/connectors/HL.asp

  10. #10
    Moderator & Master Plumber hj's Avatar
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    Regardless of what you do, a 6' post is going to have a lot of mechanical advantage over any anchors and fastenings at the base.

  11. #11
    DIY Hillbilly Southern Man's Avatar
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    I'm curious as to why a plumber would comment on a structural issue.

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    DIY scratch-pad engineer leejosepho's Avatar
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    Quote Originally Posted by Southern Man View Post
    I'm curious as to why a plumber would comment on a structural issue.
    Probably for one or more of the same reasons others of us occasionally comment on plumbing!

  13. #13
    DIY Hillbilly Southern Man's Avatar
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    Quote Originally Posted by leejosepho View Post
    Probably for one or more of the same reasons others of us occasionally comment on plumbing!
    Frankly I'm shocked at the hypocrisy!

  14. #14
    Moderator & Master Plumber hj's Avatar
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    Because he knows more than just plumbing and that was the appropriate answer. Do you want answers about electricity, heating, framing, etc. also? How about computers, because he was also a systems analyst, progammer, and network supervisor.

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    DIY Hillbilly Southern Man's Avatar
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    Quote Originally Posted by hj View Post
    Because he knows more than just plumbing and that was the appropriate answer. Do you want answers about electricity, heating, framing, etc. also? How about computers, because he was also a systems analyst, progammer, and network supervisor.
    And I know more than what the layman assumes a civil engineer does.

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