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I am pouring concrete for deck footings. I need an 18in diameter footing to carry the weight, and I will also use a 8 in diameter pier to bring it to an inch above ground. The footing must be 30 in below ground and 8 in thick. I am going to use a soil form for the footing (the hole I dig) and a sono tube for the pier.

Should I pour the footing and the concrete in one pour? I worry that the concrete in the sonotube will sink down and fill the 18 in hole while it sets, or is concrete thick enough to not worry about this? Or should I pour the footing, and then once set pour the pier. If I go this route I'll set one L shaped rebar in the footing to give support to the pier. Will an overnight set be enough?

If it matters I'll be mixing the concrete myself in an electric mixer.

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Without an integrated spread footing form (Like Sonotube tube base or Bigfoot), I would split the pours.

Pour footing: Place the rebar (A pair of L bars spaced at 7 inches apart will center tube). On the next day or after firm to firm pressure (>3hrs), place tube, back-fill carefully (to keep tube centered), tamp soil.

Pour pier: Complete the pour, add post connectors while wet or use epoxy anchoring after cure.

To be thorough, I should mention Helical Piles. Guaranteed weight bearing (they keep driving them until they reach the actual PSF rating desired).

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I agree... split the pours. Adjacent concrete poured within a period (3 days?) will bond into a contigous mass. –  John Jun 20 '13 at 12:36

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