screw piles, what kinda weight can they carry?

[[486]]

got some 12" flighting on 2.5 sch 40 pipe
thinking about using it to put up a cantilevered rolling driveway gate and a pole shed parking structure sorta thing
but I don't got a good idea of what kinda weight they're likely to support without sinking in

I could cut out additional flighting and weld it on, right now they just got the one ring at the bottom, but I've seen some of them where they got two or three flights spaced out along the length

they'll be going at least 8' down to get below frost and the dirt's mostly rocky clay with some pumping clay here and there

 

[Chzbrgr]

Maybe 2000psf. Less capacity than a 12" caisson because skin friction adds up. Extra flights can help in softer materials but you're really looking at the bottom flight area bearing. I'm not a helical pro but have done a bunch of comparisons to micro piles.

 

[[486]]

so that'd be like 1600lb apiece
four of them on say a 10x15' roof is like 42 PSF on the roof, including the weight of the roof
guess they aren't really usable for that sorta project

probably grossly unsuitable for the gate project too


Looking more and more like augering the dirt out and filling the hole with concrete and rebar is the way to go instead

 

[Chzbrgr]

Vertical bearing you're probably good to go. Lateral loads of a gate post, not so much.

 

[[486]]

Vertical bearing you're probably good to go. Lateral loads of a gate post, not so much.

it's gonna be one of them roller gates, so one end will be cantilevered 14' out and there'll be a tail 10' back to another post

the back post will be pulling up with the gate closed but the front post will have a whole lot of downward load from the cantilevered gate
not much bending moment on the post, wind load at most

Sorta like the H post in a wire fence, the posts aren't really being pulled over because of how they're tied together

 

[SLOWPOKE693]

I'd stick with the hole and concrete method for those. Helical piers are used to hold up foundations, not roofs and gates.

 

[speed bump]

so that'd be like 1600lb apiece
four of them on say a 10x15' roof is like 42 PSF on the roof, including the weight of the roof
guess they aren't really usable for that sorta project

probably grossly unsuitable for the gate project too


Looking more and more like augering the dirt out and filling the hole with concrete and rebar is the way to go instead

Eh, 42 psf is good enough for a carport. Throw enough slope at the roof that it won't build a sheet of ice and it's relatively difficult to get to 25 psf of snow on a sloped roof in most areas of the country.

To me the bigger question is how they would do with uplift. If the wind isn't crazy where you love I would be surprised if it's an issue though.