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dixie53
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# Posted: 21 Feb 2025 01:02pm
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I'm looking at building a 20x20 3 season cabin in northern Mn, what are thoughts on screw in piers? I would have them installed, not doing them myself. I'm on a river that could possibly flood so I want it a foot off the ground.
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gcrank1
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# Posted: 21 Feb 2025 01:09pm
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You might want to check what the history and projections are for flooding depth in the area.
Also on the restrictions and permitting for building in that flood plain.
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Grizzlyman
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# Posted: 21 Feb 2025 04:06pm - Edited by: Grizzlyman
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Codes/inspections in St. Louis county not required. Just land use permit “to build” and septic permit. Septic must be inspected. Not sure about other counties but would imagine it’s similar.
I know you asked about screw pilings- just trying to be helpful as you said you’re just getting started.
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Brettny
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# Posted: 22 Feb 2025 06:52am
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Those screw piles look prety good to me. Strong, wont rot and have lateral support. I would put the cabin higher than 1' though. Even with 12in girders 2' isnt much room to insulate a floor or work under there.
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DRP
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# Posted: 22 Feb 2025 08:50am
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The main issue I've heard is the lateral flex/wobbly-ness of them. I suspect you're looking at a big box Pylex product, which gets frequent poor reviews. For the contract company installed systems an article in a trade mag some years ago said it was a good idea for us as contractors to have the engineer of record check and probably upsize the piers one or two sizes above what the pile company engineers specify to help stiffen the foundation. They were, as in house engineers often do, value engineering the installation, using the lightest passable solution to the problem to get the bid rather than the best solution and then contractors were getting callbacks from unhappy clients with shakey additions. Going higher does factor into that, go carefully.
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gcrank1
Member
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# Posted: 22 Feb 2025 10:58am
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Build on a barge; ie, sort of a houseboat type?
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Brettny
Member
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# Posted: 22 Feb 2025 01:45pm
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https://www.technometalpost.com/en-US/projects/?gad_source=1&gclid=CjwKCAiAiOa9BhBqEi wABCdG89Sdh923aMSVcH2d2r1C7TiZcWNyp91zzn4hHSc9MCUl1nI14HMPWBoCczgQAvD_BwE
This is what I would consider a good screw pile. Not the big box store ones. I believe these are 3 or 4in metal posts with saddles at the top for your girder. No clue on price.
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DRP
Member
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# Posted: 22 Feb 2025 04:38pm - Edited by: DRP
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There we go, that is one of the older more established names. They do have an ESR, code approval report, go here;
https://cdn3.tptmp.com/wp-content/uploads/ICC-ES-Evaluation-report-ESR-3418-Techno-Me tal-Post.pdf
If I'm unfamiliar with a product I confirm its suitability for use by finding the report and reading it. It is approved if used as specified so find out how to use it right. Go to pg 3 on design and read that. That was a buzz kill.
Then in one of their spec documents was this footnote on lateral capacity;
5. Lateral capacity is based on medium dense soils with free head condition with a maximum distance in air or fluid soils of 6'' and embedment of
7 feet. Refer to Appendix A for additional information.
It did look like the 2.5" ones would be minimum for something of this size and I would hope to find a contractor with the equipment and geotech engineer in house. Generally to do an engineered alternative right is more expensive than prescriptive conventional if that is an option.
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gcrank1
Member
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# Posted: 22 Feb 2025 05:24pm
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Wow!
You are an absolute treasure of info, SO glad you are willing to share it here 
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DRP
Member
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# Posted: 22 Feb 2025 05:30pm - Edited by: DRP
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LOL, Thanks, I'm just a highly opinionated framer. Others say even worse things 
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Fanman
Member
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# Posted: 22 Feb 2025 09:00pm
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Quoting: Brettny I would put the cabin higher than 1' though. Even with 12in girders 2' isnt much room to insulate a floor or work under there.
This. I've done the slithering like a snake thing to get under our cabin, and it's no fun at all. Our cabin is about 4' above grade on the downhill side, and about 6" on the uphill side. Our 100 year old cabin (the ill considered uphill addition is later construction) rests on stacks of flat rocks sitting on exposed bedrock.
Those screw anchors don't look very stable. If a couple could be run diagonally on each side it would be a lot more solid.
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DRP
Member
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# Posted: 22 Feb 2025 09:28pm
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My takeaway from all that is to find a good company and consider sitting down with the engineer and making sure you get a price on a good performing setup. Most of the salespeople, as a product matures in the market and those stories go around from the first gen or the cheap knockoffs... the salespeople ask, "So you'll be wanting the improved L720 package". "Oh yeah, 720, 721, whatever it takes". When its all done and said and I've read the complaints, I've thought, welders are cheap and rebar or pipe X's between posts would brace it. You. or a local welder can fabricate gussets to brace it, all IF it is shaky. Steel has a lot going for it
Another option might be more of a post frame type with a raised floor. Simpson does have high capacity hangers that could carry floor beams on a post. In this old sketch I had, ignore/change the roof style, the wall sheathing is the bracing for the full length posts that are cantilevered from that rigid, fully sheathed box. As opposed to the typical pier and beam that is a rather loose vertical pile of poorly braced parts. Building in this style runs the loaded posts unbroken full height and braced for 2/3 of that height.
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Brettny
Member
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# Posted: 23 Feb 2025 07:32am
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For our 20x32' We chose to do 12in sono tubes right up to the bottom of our tripple 2x12 girders. We started lunch time on Thursday, dug and had the forms inspected mid day friday. By mid day sunday we where done and headed home. We used an electric cement mixer and bagged concrete. Total cost was about $700.
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dixie53
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# Posted: 26 Feb 2025 10:45am
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Thank you everyone for the feedback..
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