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I've heard a few people mention adding rebar to deck footings and piers to make them stronger, but I haven't been able to find any details on how exactly to do this.

Is it sufficient to just hammer 3 or 4 pieces of rebar into the bottom of my hole so they stick straight up and then pour the concrete over them? If not - what is the proper way to do this?

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Concrete does not have very good tensile strength. Rebar is laid in such a manner that it adds tensile strength in the concrete.

Depending on the size and weight load the pier/footer assembly is expected to support and the length of the pier, it could be reinforced in the following manner.

  1. A rebar circle in the footer to prevent weight spread from cracking it
  2. Vertical members in the pier with L bent ends that sit over the top of the circle bent piece in the footer to reinforce against bending forces in the column

For a bridge just built here, they spiral-wrapped the vertical rebar reinforcement with a long helical bent reinforcement as a seismic forces precaution to prevent the rebar from shedding the concrete (rebar doesn't have very good strength against compression and bending).

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I'm not sure what your level of expertise is, but it's important to note that footings and piers are two different things (no offense intended). enter image description here

Usually for a deck piers will suffice on their own, provided they are wide enough (typically 12" is good) and deep enough to go below the frostline in your area (3 ft deep is a good rule of thumb). The main reason you would use either footing/pier combination, or a 'belled' pier (a wider base underground) is if you'll have a roof on the deck, to protect from uplift in strong winds.

If you're actually using both footings and piers, rebar would be suggested to tie them together since you'll have a 'cold seam'; that is, you'll be dealing with two separate pieces of concrete instead of a single one.

Usually your main rebar would have a 90 degree bend near the bottom, and be fully encased in concrete, as the concrete protects the metal from moisture. You can either suspend it after the first few inches are poured, or put a couple of shorter lengths into the ground to support it while the footer dries.

Again, if you're simply pouring piers, I wouldn't worry about rebar. As long as you're below the frostline, you will be fine.

  • Well the footing and the pier can be poured at the same time right? Related: diy.stackexchange.com/questions/70064/how-will-concrete-fill-in – Brh Jul 31 '15 at 15:14
  • Also - I'm aware piers and footings are different things. I've just started researching all this stuff and at first I wasn't aware of that - so thanks for clarifying :-) No offense taken – Brh Jul 31 '15 at 15:15
  • sure, you can pour both at the same time. If you do, you don't really need the rebar, as it'll act as a single block of concrete. – DrewJordan Jul 31 '15 at 15:18
  • Hrrm - I had read that adding rebar strengthens it from side to side movement/breakage – Brh Jul 31 '15 at 15:21
  • It does, but your footings and piers won't be moving side to side because they'll be underground, except for a bit of the pier up top. anyhow, if you still want to use it, feel free. Like I said, I would put a 90 degree bend to extend out into your footing in that case, to give it some extra 'grab', and not have your rebar into the dirt where it will eventually rust – DrewJordan Jul 31 '15 at 15:23

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