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Small Cabin Forum / Cabin Construction / Pier foundation question
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socceronly
Member
# Posted: 24 Dec 2017 18:42
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If you were building a foundation on a slight slope, and using piers....

Why do people put a post tie in and then cut the posts level?

Why not cut the sonotubes down to level and put the beams into metal bracket in the pier?

I can't seem to find a Simpson product that does this. They are all post bases, and then caps for the bases for the beam.

It would seem stronger to me if the beam sat in a metal bracket with leveled concrete piers rather than leveled wood posts.

I hope that makes sense. I'll look for some pictures.

ICC
Member
# Posted: 24 Dec 2017 21:26
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Quoting: socceronly
It would seem stronger to me if the beam sat in a metal bracket with leveled concrete piers rather than leveled wood posts.


That would be better than changing from concrete in a sonotube to a piece of wood post, then the beam. My guess why Simpson does not make brackets for that is that pier foundations are not accepted by most codes and Simpsons main customers are builders in code compliant areas.

A wood post on a concrete pier with a beam on top has 2 possible rotation points; the concrete to wood post as well as the wood post to beam. Lousy idea. Removing one rotation point makes it stronger but the pier can still shift as it is only secured against lateral movement at the top end. If the earth gets water logged the piers can move in different directions as the bottom ends are only held by the dirt.

95XL883
Member
# Posted: 25 Dec 2017 12:38
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Simpson makes one. I was looking at it the other day . I’ll see if I can find a link.

95XL883
Member
# Posted: 25 Dec 2017 12:54
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Found it but I’m on my phone and can’t see the exact link. Simpson calls it a beam seat. Let me know if you can’t find it and I will try when I get home tonight.

socceronly
Member
# Posted: 25 Dec 2017 12:56
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Oooh. Thanks.

I have poured through the whole catalog. I was looking at the Canadian one though, so maybe they are not approved for abuse by polar bears.

deercula
Member
# Posted: 25 Dec 2017 21:45
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What is the actual purpose of a "metal bracket in the pier"? What harm could come if the beams are just resting on the piers? Wouldn't it take a large earthquake or very high wind/tornado to move the building?

socceronly
Member
# Posted: 25 Dec 2017 21:48
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Quoting: deercula
What is the actual purpose of a "metal bracket in the pier"? What harm could come if the beams are just resting on the piers? Wouldn't it take a large earthquake or very high wind/tornado to move the building?


The metal brackets usually have an offset built in so the wood does not contact the concrete. The post/beam would not sit in water if it collected on pier.

I have seen many beams sitting on concrete blocks, piers ect.. not sure how long it lasts or if there are measures you can take to alleviate the problem.

deercula
Member
# Posted: 25 Dec 2017 22:08
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So wouldn't the beams be sitting in water on the bracket instead of on the concrete pier? If pressure treat is used, and the piers are under the structure, would this really be an issue?

95XL883
Member
# Posted: 25 Dec 2017 23:52
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In our area, high winds are very common. Without some type of anchor, any structure, shed, etc in an unprotected area has a high chance of being moved, or worse, in a storm. Ideally, I'd like to have frost protected slab, a full basement or a footing with a stem wall to anchor my cabin. But those raise the cost significantly for what I need to be a cost conscious build.

socceronly
Member
# Posted: 26 Dec 2017 02:44
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Quoting: deercula
So wouldn't the beams be sitting in water on the bracket instead of on the concrete pier? If pressure treat is used, and the piers are under the structure, would this really be an issue?


Some I have seen do look that way. Others have what look like tabs that stop the post above the bottom and hold it there while you screw/nail in bracket. So the bottom is not touching anything. At least that is how it appears to work to me, I am not 100% sure about this. Perhaps someone else has seen this before.

You can see this in the MPBZ moment base from Simpson. I don't think the bottom of the post would touch anything, so it would be free to dry. But I could be wrong, I have only seen this thing online.

95XL883
Member
# Posted: 26 Dec 2017 09:42
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As far as water on the beams, I'm planning on protecting the beams from water by bringing the siding down. Water would have to blow in and up to get to the beams.

socceronly
Member
# Posted: 26 Dec 2017 10:11
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Quoting: 95XL883
As far as water on the beams, I'm planning on protecting the beams from water by bringing the siding down. Water would have to blow in and up to get to the beams.


The wood can wick moisture from the concrete.

snobdds
Member
# Posted: 31 Dec 2017 23:14
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I put in a pier foundation that my beams rest on. I put in big bases with Sono tubes in the middle. My beams are 4 2x12 with a bottom plate that they rest on which anchors the beams to the piers.
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socceronly
Member
# Posted: 5 Jan 2018 13:36
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Are those square all the way down, or sono tube with square base on top.

If so... doesn't that make it susceptible to frost heave?

ICC
Member
# Posted: 5 Jan 2018 17:29 - Edited by: ICC
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Quoting: socceronly
sono tube with square base on top.

If so... doesn't that make it susceptible to frost heave?


Yes, if those square pieces do not drop all the way down to frost depth they are detrimental, no help. If the square is a block like affair, a collar poured around the round tube, and the concrete filled sonotube goes lower, and if the earth freezes under the square collar you have potential for frost lift.

snobdds
Member
# Posted: 7 Jan 2018 10:05 - Edited by: snobdds
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The cabin is built on a glacial boulder field. I had to move a small hillside with my mini ex to get a flay spot to build on. There is only about 15 inches of dirt on top of huge rocks. The rocks provide plenty of drainage and there is no hydraulic pressure acting on the foundation piers. The piers are all built on top of the boulders and rebar was drilled into the rocks to tie everything together.

Most of these rocks are so big, my excavator could not even budge them. I am actually glad these rocks were there. It made it really hard to build on, but when it rains the water drains so well that a puddle doesen't last for more than 5 minutes.
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ICC
Member
# Posted: 7 Jan 2018 11:09
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It always pays to know the details.

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