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re-bar in deck footings

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  • re-bar in deck footings

    I have been installing decks for years in Atlanta, and another contractor and I were discussing footings for a deck. I said to him that I install re-bar in mine and he looked at me like I was crazy!

    Does anyone else use re-bar? Have I been doing over kill all these years?
    Of course I don't look busy, I did it RIGHT the first time!

    Nari member. CKBR, CLC

    www.attentiontodetailatl.com

  • #2
    Re: re-bar in deck footings

    the short answers are yes and no
    S.M.Titmas.

    "Truth is, everybody is going to hurt you. You just gotta find the ones worth suffering for."
    - Bob Marley

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    • #3
      Re: re-bar in deck footings

      i use it either that or i make a smaller grid work out of concrete mesh (the wide chicken wire one) and stick that in the tube.

      is there a better way??? what is overkill???
      -Sal
      ___________________________
      BSA Renovations
      Bergen County NJ's Custom Carpentry and Renovation Service
      www.BSA-Reno.com

      Handyman - Flooring - Built-Ins & Custom Carpentry - Porch Renovation

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      • #4
        Re: re-bar in deck footings

        Footings less than 3:1 (width to thickness) don't require rebar for structural capacity under "normal" conditions. What the rebar will do is help keep the footing in one piece if things don't go just right (too much water, weak spot in the soil, un-level base, too fast a cure). In larger footings, it matters because the footing has bending forces in it; in a small footing, there's really no bending, just a shear cone and direct bearing.

        There's nothing wrong with leaving out the rebar in a small, simple spread footing, but the footing is less likely to fail if something goes wrong with the pour.

        The same is true for strip footings, by the way. A 1' thick plain concrete footing will fail if you get a 2-3 foot soft spot; put a couple #5s or three #4s in it and it will probably span a 6-8 foot soft spot. How confident are you in the soil on your site?
        Disclaimer: I am a structural engineer, but I'm not your structural engineer. Check with a local PE before you try anything I suggest.

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        • #5
          Re: re-bar in deck footings

          All mine get 4 sticks of 1/2" bent at the bottom for the base. I usually use 10" sonotubes with base. We go down 5 feet minimum for frost and have seismic and (usually) poor soil issues to deal with.
          “Racism is man's gravest threat to man - the maximum of hatred for a minimum of reason.”
          Abraham J. Heschel (Jewish theologian and philosopher, 1907-1972)

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          • #6
            Re: re-bar in deck footings

            Yep, I stick rebar in my footings too. Even if they don't need it, there's always extra chunks of steel lying around and I'm too lazy to sell them...
            http://www.lavrans.com

            "He uses statistics as a drunken man uses lamp posts; for support rather than illumination." -Andrew Lang

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            • #7
              Re: re-bar in deck footings

              I put about 15 plain concrete piers under my house. They're 24" dia. x 12" thick and my engineer gave the same explanation as Jordan. There just isn't that much weight on them...

              The place I put a lot of rebar is in slabs.
              Bailer Hill Construction, Inc. - Friday Harbor, WA
              Website - Facebook

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              • #8
                Re: re-bar in deck footings

                Think of it this way: What you don't want is for the footing to fail by cracking in a circle right around the post. The weight of the structure would then push the post and the 'concrete plug' down through the rest of the footing resulting in uneven settling. The rebar makes sure that can't happen.
                HERS Rater • BPI Building Analyst • BPI Envelope Professional
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                • #9
                  Re: re-bar in deck footings

                  Hey gang, thanks again. This has reinforced my decision to continue to use re-bar in my 1' footing. I install a seat with four horizontal,two up and two at the base with a "seat" on the floor and four verticals tied together.

                  "normal" footing depths are 24" unless we don't hit stable soil, then we go deeper. In Atlanta, it's normally 15" and you hit hard, compact clay.
                  Of course I don't look busy, I did it RIGHT the first time!

                  Nari member. CKBR, CLC

                  www.attentiontodetailatl.com

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                  • #10
                    Re: re-bar in deck footings

                    Originally posted by BeachBoy View Post
                    Think of it this way: What you don't want is for the footing to fail by cracking in a circle right around the post. The weight of the structure would then push the post and the 'concrete plug' down through the rest of the footing resulting in uneven settling. The rebar makes sure that can't happen.
                    Bingo! That's why I do it, anyway.

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                    • #11
                      Re: re-bar in deck footings

                      And here I am thinking that the concrete is stronger than the soil it is resting on ...

                      The soil is going to fail not the concrete.

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                      • #12
                        Re: re-bar in deck footings

                        Originally posted by BeachBoy View Post
                        Think of it this way: What you don't want is for the footing to fail by cracking in a circle right around the post. The weight of the structure would then push the post and the 'concrete plug' down through the rest of the footing resulting in uneven settling. The rebar makes sure that can't happen.
                        i agree about using rebar in footings but are you saying that a 10" diameter x 36" deep footing will crap out a plug of concrete from the weight of the deck? that would never happen. perhaps a footing would separate from the slab and settle below grade but that's not what the OP was asking about. he wanted to know about deck footings.
                        S.M.Titmas.

                        "Truth is, everybody is going to hurt you. You just gotta find the ones worth suffering for."
                        - Bob Marley

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                        • #13
                          Re: re-bar in deck footings

                          Just out of curiosity, what size sonostube piers does most everyone use for decks?

                          Do you pour a separate footing under the sonotube or just use a 10, 12, 14" etc. sonotube?

                          How does the soil type impact your decison on the piers?

                          I am asking since I see around here in NJ, there are many decks being built with sonotube piers only (i.e. no separate footing of a pier if large larger diameter) that are marginal at best in supporting the design loads on our soil types.
                          Thanks
                          Dick
                          PS Yes I use rebar too since that was the original question

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                          • #14
                            Re: re-bar in deck footings

                            Originally posted by clydewater View Post
                            Just out of curiosity, what size sonostube piers does most everyone use for decks?

                            Do you pour a separate footing under the sonotube or just use a 10, 12, 14" etc. sonotube?
                            We generally use 10-12" and add a base similar to Bigfoots bases - all in one pour.
                            “Racism is man's gravest threat to man - the maximum of hatred for a minimum of reason.”
                            Abraham J. Heschel (Jewish theologian and philosopher, 1907-1972)

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                            • #15
                              Re: re-bar in deck footings

                              Every single deck we've done requires steel reinf. in the footing. Probably because of our snow load.

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