<UPDATE Resolved!> Quick question: New Run Build, Post Depth

[kayswagggg]

I’m building a 10’x20’ lean-to style run using 4x4 10’ and 12’ posts. Can I bury them 2’ or do I need to do 3’? And if I do 2’, I need to use concrete? I don’t want this structure flipping in any windstorms. Thank you!

 

[Sefirothe]

Depends on where you are and what your frost line is in your area.

 

[kayswagggg]

Depends on where you are and what your frost line is in your area.

Thanks for the response and for pointing me in the right direction. I looked up the frost line in my area and it say 36”. So does that mean I’ll have to dig >3’ for my posts?

And just to make sure I understand what we’re talking about first since I’m a newbie - the frost line is how deep into the earth the frost can seep and cause bulging that can disrupt your foundation, right?

And my follow-up question about the use of concrete remains: does concrete help mitigate any of the impacts of bulging and thus allow for a shallower foundation or is the depth more important for stability and longevity? Thanks again!

 

[Sefirothe]

And just to make sure I understand what we’re talking about first since I’m a newbie - the frost line is how deep into the earth the frost can seep and cause bulging that can disrupt your foundation, right?

This is correct.


Concrete wont stop frost heave. You'll need to dig below the frost line to prevent the posts heaving. Concrete will help weigh things down and hold them sturdy if you get a lot of wind. Probably for a chicken run you wont need to make actual piers or footings, but dumping a bag of Quik-crete into each post's hole and following the bag directions would be a good idea.

 

[kayswagggg]

This is correct.


Concrete wont stop frost heave. You'll need to dig below the frost line to prevent the posts heaving. Concrete will help weigh things down and hold them sturdy if you get a lot of wind. Probably for a chicken run you wont need to make actual piers or footings, but dumping a bag of Quik-crete into each post's hole and following the bag directions would be a good idea.

Great, thanks for the insight! We haven’t been super windy historically but these past few years of climate changes have brought some high velocities that are felling trees in the forest. I’m surrounded by woodlands so they absorb most of the wind, but better safe than sorry with the lean-to roof design. While I hope the sheer weight of the 10’x20’ metal roofed structure keeps it in the ground, I don’t think I’d be able to flip the structure back over if anything did happen in future years lol. I’ll do deep posts with concrete then.

My final question: if I dig 3.5’ and pour and set 6 inches of concrete, let it cure, then put on my posts at 3’, backfill with concrete and let that set, essentially creating a 6” concrete foot attached to the post, will that equal going down 42”(3.5’) and avoid frost heaving or does the post itself need to be below the frost line?

 

[Sefirothe]

My final question: if I dig 3.5’ and pour and set 6 inches of concrete, let it cure, then put on my posts at 3’, backfill with concrete and let that set, essentially creating a 6” concrete foot attached to the post, will that equal going down 42”(3.5’) and avoid frost heaving or does the post itself need to be below the frost line?

That's a bit beyond my knowledge unfortunately...hopefully someone else with a bit more construction knowledge stops by.

 

[kayswagggg]

That's a bit beyond my knowledge unfortunately...hopefully someone else with a bit more construction knowledge stops by.

Word, thanks for all your help and take care!

 

[StinkyAcres]

My final question: if I dig 3.5’ and pour and set 6 inches of concrete, let it cure, then put on my posts at 3’, backfill with concrete and let that set, essentially creating a 6” concrete foot attached to the post, will that equal going down 42”(3.5’) and avoid frost heaving or does the post itself need to be below the frost line?

Concrete does not adhere to cured concrete. It must be tied together with rebar. It appears you can pour the concrete footing at 3.5', install a post connector in/on the footing, attach the post, then backfill. However, I'd worry about the metal connectors rusting.

 

[kayswagggg]

Concrete does not adhere to cured concrete. It must be tied together with rebar. It appears you can pour the concrete footing at 3.5', install a post connector in/on the footing, attach the post, then backfill. However, I'd worry about the metal connectors rusting.

Thank you so much! It looks like there are corrosion resistant post connectors so I’ll keep that in mind if I decide to use them. I appreciate you looking things up and sharing visuals with me, as well.