Attaching 4x4 posts to concrete

Discussion in 'Remodel Forum & Blog' started by little buddy, Nov 12, 2007.

  1. little buddy

    little buddy New Member

    Messages:
    37
    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. Verdeboy

    Verdeboy In the Trades

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  3. Bob NH

    Bob NH In the Trades

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    3,317
    Location:
    New Hampshire
    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. Spaceman Spiff

    Spaceman Spiff Architect

    Messages:
    277
    Location:
    Salt Lake City, Utah
    Look here...

    http://www.strongtie.com/products/categories/post_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...
  5. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    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. leejosepho

    leejosepho DIY scratch-pad engineer

    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. Jeremiahiii

    Jeremiahiii New Member

    Messages:
    1
    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. Southern Man

    Southern Man DIY Hillbilly

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    530
    Location:
    North Carolina
    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/showpost.php?p=93773&postcount=16

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

    Southern Man DIY Hillbilly

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    530
    Location:
    North Carolina
  10. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
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    Location:
    Cave Creek, Arizona
    post

    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. Southern Man

    Southern Man DIY Hillbilly

    Messages:
    530
    Location:
    North Carolina
    I'm curious as to why a plumber would comment on a structural issue.
  12. leejosepho

    leejosepho DIY scratch-pad engineer

    Probably for one or more of the same reasons others of us occasionally comment on plumbing!
  13. Southern Man

    Southern Man DIY Hillbilly

    Messages:
    530
    Location:
    North Carolina
    Frankly I'm shocked at the hypocrisy! :eek:
  14. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,641
    Location:
    Cave Creek, Arizona
    answer

    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.
  15. Southern Man

    Southern Man DIY Hillbilly

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    530
    Location:
    North Carolina
    And I know more than what the layman assumes a civil engineer does. :)
  16. chrisexv6

    chrisexv6 New Member

    Messages:
    78
    Location:
    Connecticut
    I would get an old circ saw with a masonry blade and cut room for the posts in the slab. Drop the posts in with some sort of base molding and it will cover up the concrete edge (caulk it before you put the molding down).

    Previous poster was correct in that your posts surface mounted on concrete are gonna start to wobble eventually. I look at my mailbox post (which is actually concreted into the ground about 1.5' down) and after several years its started to move around.
  17. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,015
    Location:
    New England
    Wood will expand and contract with the seasons and the rain. Eventually, that is likely to crack the concrete. Had you considered embedding a steel post in the concrete, then boring a hole in the wood post and then setting it over the steel post? You could drill a hole through the post and pipe and then anchor it with a screw through it.
  18. Southern Man

    Southern Man DIY Hillbilly

    Messages:
    530
    Location:
    North Carolina
    As long as it's at least 12" or so away from the edge or near a control joint the post wont crack the concrete.
  19. gardner

    gardner DIY Senior Member

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    217
    Location:
    Ontario
  20. Southern Man

    Southern Man DIY Hillbilly

    Messages:
    530
    Location:
    North Carolina
    From your link:
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