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Author Topic: Pole barn anchor blocks  (Read 560 times)

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Offline Polish Hammer1

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Pole barn anchor blocks
« on: September 14, 2021, 06:54:05 AM »
I was pricing out a pole barn for future build 40x80 x12 and going through the list through Menards it says treated anchor blocks not sure what it was looked it up and all it is is a 12Ē treated Board screwed to the bottom of the post that will be buried in the ground back filled with gravel. So after looking at I was wondering is this really a good way to go for up lift of posts? I know some guys do rebar but to me drilling a hole in the wood then buring it donít seem the best either could be wrong. If this is good then for how many I need I would just buy the boards an save half the price and cut them down. Live in Wisconsin wind really isnít much of an issue

Offline Don P

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Re: Pole barn anchor blocks
« Reply #1 on: September 14, 2021, 07:23:24 AM »
First look at down. The footing provides a snowshoe that spreads out the load to prevent the post from sinking. Quantify the load on the post and the bearing capacity of the soil. Is a 1' square a large enough footing. Typically plans assume 1500-2000 pounds per square foot bearing capacity in the soil, what is the post load? Then see if the footing is large enough.

Assuming so the next concern is punch thru, A single 2x12 with a post on top is probably subject to the side "wings" splitting off. I've seen 2 pieces turned 90 degrees from each other to help prevent that. As they get larger chunks of 4x6 or 6x6 sammiched between 2x lumber to form the footing are used.

Uplift. A well secured footing should pull up the inverted cone of soil that sits above it. Does that cone weigh more than the uplift force. If not make the footing larger or attach larger wings made of boards to the post low in the hole, grabbing a bigger chunk of earth. Rebar works in many applications and the holes are below the oxygen zone, no air no rot, rot is  surface thing.

Then side to side. If the post is resisting lateral wind loads on the building you've entered engineer land. a rather complex interaction between post dimension, embedment and soil type. Avoid that nonsense and use wall sheathing if possible.
The future is a foreign country, they will do things differently there - Simon Winchester

Offline mike_belben

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Re: Pole barn anchor blocks
« Reply #2 on: September 14, 2021, 09:54:37 AM »
My brother has spent the last 6 years of his precious monents away from work, jacking up a very old (hand hewed) 2 story barn that was relocated in the 1990s as a pole barn and promptly rotted out.  

@Bargemonkey has a 200ish yr old hay barn on a loose fieldstone foundation with a timber sill that hasnt a spec of rot that i could see.  

I routinely make sawdust and grass into topsoil very fast.  When i ammend my garden between cycles it is by adding woody material to add organic matter content. 



So those are 3 examples im giving you to say dont put wood in dirt.  Put wood on stone or cement with an asphalt type barrier such as discarded shingles facing down,  between them.  


No one needs to create a falling down barn problem to deal with in their elderly years and i personally feel thats exactly what wood in dirt, or blown off neglected tin are designed to do.  My $.02
Isaiah 63:10

Offline farmfromkansas

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Re: Pole barn anchor blocks
« Reply #3 on: September 16, 2021, 03:56:12 PM »
Menards sells some anchor plates for pole barns that bolt down to a concrete pier, you take 2 and bolt through your pole, and then use anchor bolts to anchor the pole down to the pier.  I would use a 18" auger and dig a hole about 5' deep, because that is how deep my auger will go.  Some neighbors built a 80 x 125 x 18' sidewall steel building, their piers are 24" x 6' deep.
Most everything I enjoy doing turns out to be work

Offline Don P

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Re: Pole barn anchor blocks
« Reply #4 on: September 16, 2021, 10:01:06 PM »
Here I often see owner builders go about 2 or 3' deep which is fine frostwise here but if they are trying to pick up bracing for the posts from the soil there is a thinking problem going on. Most people look at the surface of the ground as the rotational point of the post, as if the surface of dirt or gravel was solid. The reality is the post is rotating around a point between the footing and the surface, within the soil. When a post is constrained by a slab at the surface, then that point of rotation moves up. But also look at the length of that lever above ground in the wind. No matter how good the ground that is insufficient bracing alone. Here's a typical pic;



 

 

 
I saw more than one on the computer when uploading but they kind of help tell the story.

Then, when Mike wants to plant a pier to avoid a post in the ground the conditions change again. Now, just above the ground line draw a hinge, fixed in place but free to rotate. The ground bracing just disappeared, look around and get that stiffness back somehow.

My neighbors with the very shallow posts (5-7' deep is considered a "shallow post footing"),after a few years they are pushing with tractors and pulling with diagonal come-alongs trying to get the building plumb and better braced.Like I said it seems to be a thinking problem, they are seeing the building but not really thinking about what makes it work so there is a halfway blend of building types without a full understanding of what, where, and how they are resisting the forces on the building.
The future is a foreign country, they will do things differently there - Simon Winchester

Offline mike_belben

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Re: Pole barn anchor blocks
« Reply #5 on: September 17, 2021, 11:05:21 AM »
well lemme piggy back onto this one while its fresh in your mind.  timber frame on a monolithic slab, with cordwood infill encasing the entire frame so that the frame timbers are not exposed to the interior or exterior. (a lime based mortar is used for breathability to all sides, big roof overhangs obviously)

that infill structure is going to unitize the walls and frame posts into a monocoque sort of structure and lock things up, right? akin to what ply type sheathing on both sides will do, i imagine.  given that the mortar to cordwood bond integrity stays sound, of course.
Isaiah 63:10

Offline Don P

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Re: Pole barn anchor blocks
« Reply #6 on: September 17, 2021, 06:19:47 PM »
Yup, but to the flippin rules  :D, the burden of proving that your alternative braced wall is capable is on you if he asks for it.

...(I'd bet in that case some steel tension X's of Simpson strapping buried in the middle of the infill and you're golden)
The future is a foreign country, they will do things differently there - Simon Winchester

Offline mike_belben

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Re: Pole barn anchor blocks
« Reply #7 on: September 17, 2021, 07:16:38 PM »
lots of cordwood builders have gotten together and have come up with the smart guy numbers for stickler states.  im not a smart guy so i wouldnt know much about all that stuff. 
Isaiah 63:10

Offline Don P

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Re: Pole barn anchor blocks
« Reply #8 on: September 17, 2021, 08:48:42 PM »
Uh-huh, you probably know more than them  :D
Mainly, can it withstand the shear as the frame tries to rack. Plywood, board, steel let in bracing, etc, all those methods of wall bracing have been done and tested to the point that they are prescriptive in the residential code. Once you step outside the prescriptive stuff it enters engineer land if the inspector wants. Info like you spoke of, if you present it and talk about it like a smart feller that understands it, competent not debate club, can go a long way towards being told to proceed on your own. there is a reason to know all those flippin rules. I've been doing push-ups with that NFPA 211 book, pushin it up off my nose, yawn and try to read it again.

I called for a footing inspection Wed. Got home this evening to a message, sometime Monday. Which unless he is early, is Tuesday to pour. I had hoped to be laying block Monday. They know I have no fear of a shovel or bending rebar, I love it.
The future is a foreign country, they will do things differently there - Simon Winchester

Offline mike_belben

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Re: Pole barn anchor blocks
« Reply #9 on: September 17, 2021, 09:51:41 PM »
i can relate.  

im a low level insomniac and read boring, technical stuff every night to fall asleep.  after dozen or so wacks in the face i plop it on the nightstand and close my eyes on purpose. 

then the alarm goes off what feels like 15 minutes later and its groundhog day again. 
Isaiah 63:10

Offline farmfromkansas

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Re: Pole barn anchor blocks
« Reply #10 on: September 19, 2021, 12:13:59 PM »
Wish I could sleep all night like that.  I'm up at least a couple times at night.  Sometimes for  2 or 3 hours.
Most everything I enjoy doing turns out to be work

Offline mike_belben

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Re: Pole barn anchor blocks
« Reply #11 on: September 19, 2021, 02:44:38 PM »
Wish I could sleep all night like that.  I'm up at least a couple times at night.  Sometimes for  2 or 3 hours.
Nah, i just left that part out.  I cant sleep before 11, more often midnight or 1.. Then its either drama outside or having to pee that wakes me up once or twice more.  Then 530 gotta get up and get the kids ready.  Im always beat. 
Isaiah 63:10


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