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Thread: Deck Construction

  1. #1
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    Deck Construction

    Considering having a deck built. It is a bigger project than I want to tackle myself. One contractor is telling me that setting the support posts is best done by digging the post holes per local code (42" deep) pouring a concrete footing the set in the posts and back fill. He does not fill the entire hole encasing the post in concrete because they will rot faster if encased in concrete.

    Thoughts......
    George

    Making sawdust regularly, occasionally a project is completed.

  2. #2
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    That is the way we set posts for pole barns that way the frost here will not have something to grab and heave

  3. #3
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    Wood below grade is never a good idea. The concrete should be extended above grade and the wood post attached with the proper bracket. Look at these for an idea; http://www.bigfootsystems.com/index.htm

  4. #4
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    A concrete pier that extends below the frost line is necessary to prevent upheaval from frost. Further I prefer to use galvanized metal post supports by Simpson Strong-Tie, or similar, sitting on top of the concrete pier above ground rather than immerse the posts into the concrete with rot developing with time. Having the post (pressure treated) ends above grade & exposed to the air will prevent the posts rotting in the concrete.
    Last edited by Al Launier; 08-10-2017 at 8:23 AM.
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  5. #5
    Just a few days ago I heard that pressure treated posts are not allowed in ground anymore. Have not looked for details .

  6. #6
    Around here the go to seems to be screw piles / helical piers because of the soil and frost. They are quick and have various post holders that fit the top of the pile. If they are available in your area you should look into them.

  7. #7
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    Quote Originally Posted by George Bokros View Post
    Considering having a deck built. It is a bigger project than I want to tackle myself. One contractor is telling me that setting the support posts is best done by digging the post holes per local code (42" deep) pouring a concrete footing the set in the posts and back fill. He does not fill the entire hole encasing the post in concrete because they will rot faster if encased in concrete.
    I've been told at posts that get wet will sometimes rot more quickly if set in a pocket of continuous concrete under and up the sides of the posts. Water will evidently move down the post and get trapped at the bottom. I don't know if this is true since I've never excavated and inspected one set that way.

    What I do is drill the hole and make what we've always called a concrete "punch pad" at the bottom of the hole. Then I put a little gravel on top, set the post on the gravel, then fill with gravel, soil, concrete, or some combination. The theory is any water that moves down the post will have a way to drain. When the post will be in the dry as building support, I'll fill the upper part of the hole around the post with concrete when pouring the floor, tying the post to the rebar in the floor.

    Another way I've built decks is drill a hole well below frost line and make a pier with concrete and rebar, formed to put it about 4" above ground. Set the post directly on top of the flat pier, held in place with a length of rebar set into a hole drilled into the concrete and into the bottom of the post. I built a 7-level 1000 sq ft deck this way using 4/6 PT posts and it's been fine for 40 years now. I was not concerned that wind would lift this deck due to the way it was tied to the house overhead and the location. The building inspector was happy with the construction, joked about sending some contractors by for deck-building lessons. Ha.

    I've also backfilled the holes but still with the post resting on a concrete pad below the frost line.

    Regardless, you might check the code and with the building inspector in your area.

    JKJ

  8. #8
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    You will get a myriad of various replies on this question.

    In MY opinion, My studies preparing to build a Pole Building... in or at ground level, use proper treated wood...CCA .80, not less, not .60, and you will be good.

    The above is very proven.

    Google it.

    As far as the backfill, everyone has opinions, jury still seems to be out on that.

    Yes, it would be better for wood longevity NOT to have any below grade, BUT there are other tradeoffs, mostly in layman terms like wind resistance, being a "hinge" point no matter how well you do it... Still a hinge point.


    Using the new treated stuff because some 1/100,000,000 goofy kid will come and eat it like a Beaver, .. all bets are off.

    The move from CCA is mostly BS.


    Again, broken record here, study it yourself.

    And read Tech articles, not what someones MawMaw's Cuzzin sed.

    Marc
    Last edited by Marc Jeske; 08-10-2017 at 5:12 PM.

  9. #9
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    Quote Originally Posted by George Bokros View Post
    One contractor is telling me that setting the support posts is best done by digging the post holes per local code (42" deep) pouring a concrete footing the set in the posts and back fill.
    If your local code defines what is needed you would be wise to follow the code so you don't run into problems if code enforcement happens by. You might also want to check to see if a permit is required to build a deck.
    Lee Schierer
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  10. #10
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    As Lee said.

    Start from there, then.. IF you have options, study them.

    Marc

  11. #11
    Just re read all and don't see any comment on ban on pressure treated posts in ground. Is that catching on in some places, or is that just a "green practice" suggestion? Thanks

  12. #12
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    Quote Originally Posted by Al Launier View Post
    A concrete pier that extends below the frost line is necessary to prevent upheaval from frost. Further I prefer to use galvanized metal post supports by Simpson Strong-Tie, or similar, sitting on top of the concrete pier above ground rather than immerse the posts into the concrete with rot developing with time. Having the post (pressure treated) ends above grade & exposed to the air will prevent the posts rotting in the concrete.
    +1 on this method. I have build several decks and outdoor structures using this method.

  13. #13
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    Here is a design guide for decks that meet the 2012 building code. Note that local building codes can be more strict than the national code.
    Lee Schierer
    USNA '71
    Go Navy!

    My advice, comments and suggestions are free, but it costs money to run the site. If you found something of value here please give a little something back by becoming a contributor! Please Contribute

  14. #14
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    A tried and true method is to dig the hole below the frost line in your area, set a SONTUBE of the chosen dia. - 6" for a 4x4 post , 8" for a 6x6 post, fill with concrete so that the concrete is above grade a few inches to 6" (ideally all at a relative level height but that it nitpicking) then set a PT post on top of that using a Simpson Strong Tie post base -

    ABU66Z_1_375.jpg

    This will last 30 years or more without concern. Easy and effective and no question about that it works. The number of posts , the need for inter post bracing and how the deck is secured to the building are all variables based on height, sizing and calculated load. There are other systems for setting footings in soft ground that might need to be considered but the final result of a PT post sitting on concrete above ground is a good method.
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  15. #15
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    George go to the building department and get a copy of their requirements or ask the inspector what he wants. I always liked talking to the inspectors and asking them how they want something done this is when I traveled around to install Revco drugs stores. Most of the time they were very helpful and easier to deal with

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