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Want to use 1.5” galvanized poles concreted into ground with holes drilled near ends. Frost line here is mere 24” so can I just concrete a 12’ pole into 2’ or do I have to use some kind of formula to determine how deep to install pole I have 3 rectangular sun sails that will be attached.

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    2' sounds to shallow, even 6' fence posts should be 3' deep
    – Ruskes
    Aug 24, 2022 at 7:47
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    Frost is one concern. The force of the wind against the sails is the main concern. 2 feet of dirt will not give enough support against the wind. The 1.5 inch pipes might also be not strong enough. Each pound of wind force at ten feet will equal 10 pounds at ground level.
    – crip659
    Aug 24, 2022 at 10:34
  • In case you're wondering how many pounds of force you can expect on your sail, here's one calculator that will tell you. If you don't like those numbers, an internet search for "calculate force of wind against a surface" will bring up a dozen other calculators. (That just happened to be the first response - no endorsement or guarantee of accuracy.)
    – FreeMan
    Aug 24, 2022 at 12:05
  • Will the poles be self supporting or will you use bracing wires/cables for extra support?
    – crip659
    Aug 24, 2022 at 12:59
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    Does this answer your question? Installing long 20ft metal poles in concrete around a football pitch There are several other similar questions, too.
    – isherwood
    Aug 24, 2022 at 13:56

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If you make the footings wide enough 2' depth will work.

Poles for a shade sail will see significant sideways forces at the top (and thus toppling forces at the base) so you will need heavy footings.

So your for a good result your footings will be wide or deep or both. or pour a slab and bolt your poles to that.

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  • This answer would be better if "wide enough" had a number attached. (My intuition is that it would have to be really wide.)
    – Aloysius Defenestrate
    Aug 24, 2022 at 13:58
  • without knowing the number put on rectangular or the strength of the winds it needs to withstand, or being an engineer, I'm not going to put a number on it.
    – Jasen
    Aug 24, 2022 at 22:19

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