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CJHames
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# Posted: 2 Jan 2011 17:59
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Howdy all,
Me and my son are planning a pole barn as a residence. I've read several books, and looked at many websites, and I can't see an instance in which the entire hole (in our case 4' deep) has been filled entirely with just cement. I've seen four basic pole setting techniques listed:
1) a small concrete footer poured at the bottom of the hole that the pole just sits on. The remainder of the hole is backfilled with the dirt that was removed from drilling the hole.
2) the pole embedded in a relatively small amount of concrete, perhaps 1/3 the total size and depth of the hole, with the remainder backfilled with dirt.
3) A soil/cement mixture at the bottom of the hole with a "concrete necklace" (using lag screws) about 1/4 of the way down the hole and the remainder filled in with soil.
4) A soil/cement mixture backfilled in the hole.
Can anyone tell me why I've never seen the entire hole and pole filled in with 100% concrete and rebar? Is it simply because of cost? Is there a structural issue in doing it this way? Is it because it may make the poles harder (or impossible) to remove if need be at a later date for some reason?
I want the poles to be as firmly placed in the ground as possible, and this seems like the most permanent and best way to do it to me, but what do I know?
Any info you all could give me would be much appreciated. Thanks very much.
CJHames
North Texas (near Paris)
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Borrego
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# Posted: 2 Jan 2011 18:17
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Hi CJ - I'm building a pole house in the SW desert and probably from many of the same books and resources you've found. I set my poles just in the sand and rocks.
Once you've locked the poles together with the double 'girders' you want a little bit of movement. Plus the concrete is just unnecessary, no reason for it at all - that's the point of pole building. I know it goes against the grain of all we've learned (I'm a builder by trade) but it's been done for hundreds of years.
The 'necklace' is for slopes, and the 'pad' is for real sandy areas so the poles don't sink..
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CJHames
Member
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# Posted: 2 Jan 2011 18:29
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Well thank you Borrego, I appreciate the quick reply. Now I just need to find out the definition of how sandy is "sandy."
I like your pics, they are an inspiration. Is there anything more beautiful than seeing that first pole in the ground? You know, except for seeing it all built.
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MtnDon
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# Posted: 2 Jan 2011 18:44
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Concrete poured around a wood pole/post/pier will hold moisture more so than just soil itself. Untreated wood plus moisture = rot. I would simply pour and tamp the dirt that was removed.
A concrete footer is usually a good idea if there is any doubt as to the weight bearing ability of the soil. It should be poured to a thickness about half the length/width dimension. IE: a 16x16 pad would be about 8 inches thick and have rebar added in either an X or a # shape at about midthickness.
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CJHames
Member
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# Posted: 2 Jan 2011 18:59
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Thanks MtnDon, that helps a great deal. Our other thought was to auger down 4 ft and use 12" x 4' cardboard pier tubes, with a good amount of rebar, and run the poles entirely above ground. But again, as far as structural superiority goes, I'm not so sure just having the poles attached to a Simpson plate is stronger than having poles buried in God's good earth.
While we haven't yet decided for sure, there is a good possibility atleast half of the structure will have a second story, and maybe the entire building.
Any thoughts?
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fpw
Member
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# Posted: 2 Jan 2011 19:35
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Filling a hole with concrete and rebar works fine.
http://peelinglogs.blogspot.com/2008/09/blog-post_21.html
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CJHames
Member
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# Posted: 2 Jan 2011 20:02
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Thanks fpw. I had looked at your site and thought it was terrific. I think we'll make a few test holes tomorrow when we're out at the property and see what works best.
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Borrego
Member
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# Posted: 2 Jan 2011 21:54
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CJ - Here is the site I found initially. It has a few 2 story and larger dwellings.
Unless you have nothin but sand, you'll be fine. As Mtn Don noted, the concrete will hold water, hence the lack thereof. Of course, you'll be using treated poles and make sure to coat the bottom cuts....
http://www.scribd.com/doc/11992924/Pole-Building-Construction
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CJHames
Member
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# Posted: 2 Jan 2011 22:40
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Yes sir, I read that manual yesterday. Good stuff.
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Stein
Member
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# Posted: 3 Jan 2011 13:36 - Edited by: Stein
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One of the reasons that most posts are either cast around the bottom or, in my case, pinned with rebar that goes under the pad and then driven into the post is to resist frost heaving.
When I say pinned, the precast pad is placed in the hole. There are two slots in the pad. Two pieces of rebar about 3' long are bent with two legs about 3" long. One leg goes in the slot in the pad, trapping it under the pad. The other leg goes up on an angle until it hits the post. It is then driven into the post or a hole drilled and then it is driven into the post, holding the post down to the pad. Seems crazy to hold it "down" but frost heaves can actually jack an unpinned post out of the ground over time. The pin/pad combo creates a cleat under the soil that is on top of it. I would suspect that a solid filled hole with concrete would be easier to frost heave out of the ground than a cleated post.
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MtnDon
Member
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# Posted: 3 Jan 2011 15:26
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If the pad is not below expected frost depth the expansion of the soil under the pad as it freezes will lifts the entire pad and post.
It is also possible freezing and expanding soil around a post to cause lift. That happens more with rough posts or posts that are wet and freeze to the soil/water in the soil.
A poured concrete footer, below frost depth, with a concrete pier (cast in a round sonotube) that is tied to the footer with bent rebar will not move
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CJHames
Member
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# Posted: 3 Jan 2011 21:33
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We went out to the property today and visited with a few neighbors to see what they have done and how they built. We were advised by one fellow to NOT use post and beam or pier and beam in the area we live because the soil was just too bad. We were told of one home that had shifted off it's piers just a year or so after building. We asked if we could take a look at the home and they happily obliged.
It was the sorriest piece of engineering I've ever seen. I think a 5-yr old with an erector set would have done a better job. Telephone poles were cut and placed down in the soil about "2 or so feet" and then they pounded soil back around the poles. The poles extended about 2.5' up out of the ground, and the house was built on top of this "frame." The poles weren't joined together in any way. Just a bunch of stumps basically in the ground with 2 x 6 joists running along the top. The man we were speaking with was a brother of the owner of the house, and he had helped build it. He was shocked that the house was sliding off of the exterior poles (the poles were starting to lean, becoming off plum).
He went on to tell me how post and beam just "wouldn't work out here." When I asked him why they didn't use any concrete in the holes he said "how would concrete have kept these poles from moving? Seems to me the concrete and the poles weight just about as much and the concrete just would have shifted as well."
The most successfully built homes or cabins in our woods have all been placed on top of concrete blocks that sit flat on the ground and the joists have been built up on top of the blocks. Seems crazy to me, but we looked at enough of them to see that they indeed worked.
I am as confused as ever. I want stability. I want to do it right the first time. What's more, we need to do it right the first time. Don't have the money or time to do it twice. Has anyone out there built their cabin simply on top of concrete blocks and had any success?
Thanks very much, I've appreciated all the posts and the input from all of you. This is a terrific site and a great forum.
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Borrego
Member
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# Posted: 3 Jan 2011 21:51
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The whole beauty of the pole system is that once the poles are tied together with double girders, top and bottom, you could set the whole thing on top of the ground if ya wanted to..... it won't go anywhere...
If you want to go with the traditional footing approach, it is certainly a great way to build, just different than the pole system.....
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CJHames
Member
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# Posted: 3 Jan 2011 22:24
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Thanks Borrego, that's what I was thinking. I just don't see how this won't (structurally) succeed.
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fpw
Member
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# Posted: 3 Jan 2011 22:38
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There are many cabins built with blocks on grade. Sometimes they stay level for years, sometime they shift. Depends on the soil, frost heave, etc. If I was to build on grade with blocks or pads, I would install some type of heavy duty screw-jack so that you could adjust the jacks if needed due to any frost movement.
I like holes below the frost line, belled out at the bottom filled with sack-crete and rebar. Anything you build off this will not shift.
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Borrego
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# Posted: 3 Jan 2011 22:44
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Quoting: CJHames Thanks Borrego, that's what I was thinking. I just don't see how this won't (structurally) succeed.
Well, i figure if it settles a little over the years, you can just jack it up and put a footing there. Not that it will, but worst case...?
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CJHames
Member
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# Posted: 4 Jan 2011 08:51
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Thankfully we're in North Texas, and I'm not sure we even have a frost line down here. We did get some very cold wind chills last winter (like 19 below) but it was a two day event. Most frost we get exists only on grass and on roof tops most of the time. Where we're building we don't even have to file for a building permit. No inspections. The one thing we do have to do is get a septic permit and inspection.
OK, one last question (I hope) has anyone ever had any experience with these? I think they will help us to secure the poles 4' into the ground and bury it in cement.
http://www.postprotector.com/
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CabinBuilder
Admin
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# Posted: 4 Jan 2011 09:58 - Edited by: CabinBuilder
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Quoting: CJHames ...poles were cut and placed down in the soil about "2 or so feet"
If you choose posts for the cabin foundation, you need to dig post holes well below the frost line. The frost line depth depends on climate in your area.
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MtnDon
Member
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# Posted: 4 Jan 2011 10:57
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I have seen those post protectors. There are other brands too.
I wonder how effective they are. I see water getting trapped inside them holding moisture in the wood. I also see they still recommend PT wood. Also I wonder if those ridges around the outside do good or harm. IF there is freezing ground they would provide a lift point. Just things I wonder about.
I believe the soil there has clay content. That is probably the main concern. When it gets wet it looses it's ability to support weight and to resist lateral movement. Adding concrete around the posts will not help that rotation and tilting when ground with lots of clay gets wet.
Sometimes the clay does not go very deep. If that's the case then digging down and pouring concrete pads below the clay will provide stability to prevent sinking. You would still have the lateral movement issue but if each post is then properly braced to the beams and joists that will hold them vertical.
Sometimes a concrete or concrete block perimeter foundation on a continuous footer will work.
I was going to suggest checking with the county to see what they recommend, however if they do not require permits they may not have any suggestions. Might be worth asking though.
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CJHames
Member
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# Posted: 4 Jan 2011 11:13
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MtnDon,
I wondered the same thing. Isn't this creating basically a "swimming pool" type effect? If any water does get inside it has nowhere to go.
Our soil where we currently live (about 20 miles north of Dallas) has awful clay. Can't hardly get it to come off a shovel, and many times you can't. You have to use your hand to scrape it off. It's the worst I've ever seen. The soil at our property (120 miles NE of us) is not quite sandy loam, but it isn't the clay crap we have down here. Doesn't stick to shovels, etc. It has some clay but not much.
I think we're going to be fine. My fears have been much alleviated, thanks to you all. Now we're looking for good plans for a 32x48 and materials list, etc. Gonna rent a Bobcat and level the site some asap and then get the site stringed out and start digging some holes. Can't wait. We're going to go with 4x6 dimensional lumber rather than poles.
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Jerry
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# Posted: 5 Jan 2011 00:09
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A very interesting topic. Lots of good advice. I built a cabin when I was a lot younger that sat on top of a ridge overlooking a river. The soil was sandy loam, and the older guy I was building with built forms for concrete that sat right on the surface. These blocks of concrete would hold the main cabin support beams. After building the cabin, and after the first winter we immediately noticed the beam supporting the center of the building heaved equally to the beams supporting the outer walls, but didn't settle as much. After five years this was magnified to the point that there was a hump down the middle of the cabin. We sold it.
Fast forward twenty years. I bought property ten miles from the first cabin, but this soil (on a small lake) was primarily sand. I built a small cabin and used the post and beam method for the foundation. I augered down about 4 feet, poured a deep concrete footer, tarred up the bottom 12" of some ground contact rated 6x6 treated posts, and set them 4" in the wet concrete. Ten years later nothing has moved.
I also ended up buying the cabin next door which was built 60 years ago on concrete blocks placed right on the ground. Other than some evidence that the foundation had been slightly tweaked over the years to level it out, it's basically the same as when it was built. I added a deck this year, also built on the ground to match the cabin, so we'll see how that survives the winter.
The bottom line for me when considering a cabin foundation is first, what kind of soil are you dealing with? Next, what is the coldest winter temperature? And budget is always in the mix. But no matter where I was building I'd always want the buidling attached to a foundation that extends into the ground, the further the better for resistence to the wind. I've also learned that animals like a low, open foundation for a hiding place, and for that reason, and to allow for ventilating moisture, I'd keep an open foundation elevated at least 18".
Just some thoughts based on my experience.
Good luck to you in whatever method you choose.
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CJHames
Member
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# Posted: 5 Jan 2011 06:58
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Thanks Jerry. I called our county supervisor yesterday and he told me the same thing. The soil out where we live can very greatly on parcels just 1/4 mile apart from each other, maybe less. Ours is a mix of light clay and sand. Both he and the building expert at the local lumber yard said they absolutely see no problem with 4' holes and a post and beam construction.
One of our main concerns is wind. Here in north Texas we get those swirling things every now and then. Can be quite nasty. Of course, when they're swirling at F3 or better, it probably won't matter much if there's a direct hit. We'll just rebuild I reckon. :)
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elkdiebymybow
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# Posted: 17 Jan 2011 01:08
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I just stood up a storage garage for my sleds. I dug the poles in a minimum of 3' and backfilled using the excavated soils. The soil at our place is a course sand and very small aggregates. Poles were very sturdy after backfill and tamping. When all was tied together the building really became solid. An old timer told me to pour diesel fuel around each pole for extra protection against moisture and rot. If I had the time I would have treated them with a product called "copper green". (home depot/lowes etc.. carries it). It basically gives the poles the same treatment as pressure treated wood and is actually better in my estimation because you can really get a deep soak. No need to concrete to poles as the concrete will tend to hold moisture and lead to rot.
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elkdiebymybow
Member
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# Posted: 19 Jan 2011 00:42 - Edited by: elkdiebymybow
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Borrego
Love to see some updates on your build out.
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CJHames
Member
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# Posted: 19 Jan 2011 08:02
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Borrego -
Who are you asking for the updates from?
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Borrego
Member
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# Posted: 19 Jan 2011 15:29
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CJ - elkdie is asking for them from me. I have just found the poles I need to finish my basic structure, so I will be in the desert this weekend and will post pictures soon.
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