Author Topic: Advice on unstable feeling foundation  (Read 283 times)

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Offline ethulin

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Advice on unstable feeling foundation
« on: August 14, 2020, 06:27:08 AM »
We have built a cabin based on the 12x18 Little House Plan design. At this point, the construction is sheathed, roof on, etc (although the interior is not complete.

The structure feels quite unstable. When you move around you can feel the structure move with you. This feels pretty concerning, so we are looking for advice for what we may need to do to address it.

A perhaps related problem is that one of the two primary beams under the house has significantly cupped. I am attaching photos of this. this cupping is happening almost entirely in one corner (by the middle of the beam, it is pretty straight).

Photos here: https://imgur.com/a/1n6GDjU

Your suggestions for what to do about the instability of the foundation overall as well as the cupping beam are very much appreciated!

Online Don_P

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Re: Advice on unstable feeling foundation
« Reply #1 on: August 14, 2020, 11:28:04 AM »
Uhhh, the cupping is the minor issue. Check the plumb of those unbraced posts, you're about to collapse. Stay out until you crib it up tight then excavate to frost depth and put a foundation under it. How many times do we have to have this conversation. One engineer who monitored this site for awhile said he would watch the light bulb slowly come on time and time again. I realize people don't know what they don't know, that is not a foundation it is a collapse mechanism.

Offline akwoodchuck

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Re: Advice on unstable feeling foundation
« Reply #2 on: August 14, 2020, 08:43:59 PM »
I call it "designed to fail"....TIM-BERRRRRR!!!!
"The lyf so short, the craft so long to lerne."

Offline MountainDon

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Re: Advice on unstable feeling foundation
« Reply #3 on: August 16, 2020, 01:00:38 PM »
Hmmm.  This problem was originally posted in 2016, similar photo.
https://countryplans.com/smf/index.php?topic=14389.msg188074#msg188074

Was anything done since 2016 to correct the problem?
Just because something has been done and has not failed, doesn’t mean it is good design.

Online Don_P

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Re: Advice on unstable feeling foundation
« Reply #4 on: August 18, 2020, 01:54:24 AM »
I prefer my response in that thread  :D

Offline ethulin

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Re: Advice on unstable feeling foundation
« Reply #5 on: August 20, 2020, 08:19:40 AM »
Check the plumb of those unbraced posts, you're about to collapse. Stay out until you crib it up tight then excavate to frost depth and put a foundation under it.

Thank you for the very appreciated warning. Checking the plum on the posts, the one in the photo is not plum, the one directly down the beam is out of plum though significantly less, and then the other 4 are quite plum.

And thank you for the direction that the foundation needs to basically be redone (or as I am getting the impression, be done, because what we did isn't sufficient). I had thought we had followed the bracing instructions in the plans, but am realizing now that where we should have done lateral bracing, we put in bracing parallel to the beam (or maybe we needed both). I now get how royally stupid that was...

I feel really dumb asking this, but what does it mean to "crib it up tight"? In your response to my 2016 thread you talked about laterally bracing the good locations, then working the tipped end back into plum. Is that what you mean to crib it up tight? If so, could you possibly give a bit of guidance about how we might go about tipping beam/posts back into plum? I see why that is so important, but I am just not even sure how one would go about doing that.

In terms of putting a new foundation under it, completely accept that that is needed. However, I am really unsure how how to go about doing that. Right now it is on the 6 deck blocks as found in the Little House plan. I assume you are saying that simply adding multiple lateral supports (i.e. 45 degree mitered supports from the beam up to the structure after we get the beams and posts back into plum) is insufficient. If there is any more guidance you could give about how to go about adding what is needed for the foundation at this point, I would very much appreciate it.

Hmmm.  This problem was originally posted in 2016, similar photo.
https://countryplans.com/smf/index.php?topic=14389.msg188074#msg188074

Was anything done since 2016 to correct the problem?

Sorry for starting a new thread if I should have continued that one. I had an injury in 2016 which prevented me from doing any work on it and am just getting back at it now trying to salvage. So the honest answer is no, but I am trying to learn what I need to now to deal.


I hope this all comes off the way I am meaning it: I totally see we royally messed this up, and now am just scrambling to try to learn as much as I can about how to fix what we messed up as best as we can. The help from you guys is greatly appreciated (despite the frustration I can imagine in dealing with what would seem like such an obvious issues).

Offline akwoodchuck

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Re: Advice on unstable feeling foundation
« Reply #6 on: August 21, 2020, 08:31:19 AM »

I feel really dumb asking this, but what does it mean to "crib it up tight"?

https://en.m.wikipedia.org/wiki/House_raising
"The lyf so short, the craft so long to lerne."

Offline ethulin

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Re: Advice on unstable feeling foundation
« Reply #7 on: August 21, 2020, 08:39:58 AM »
https://en.m.wikipedia.org/wiki/House_raising

Thanks. I see how that would be the required first step in putting some sort of new foundation in. I had taken Don_P's comment about cribbing it up tight as something that is done prior to keep it from falling over in the mean time to make those posts plum and add lateral support. But given my past track record, very possible I misinterpreted!

Online Don_P

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Re: Advice on unstable feeling foundation
« Reply #8 on: August 21, 2020, 05:48:25 PM »
Basically you need to support the building, dig down below frost depth, pour a footing and then lay block or form and pour a foundation under it. It looks like there is room outboard of the current beam to nail a treated 2x8 flatways to the rim and across joists to serve as a mudsill assuming the joists will span a few more inches safely.

I started digging under a 120 year old house this week so we can do basically the same thing. The house was built on a loose rock foundation that has shifted and settled. It is not fun or glamorous work. We are doing it in small sections, we've supported just outside of the dig area and will pour the first 2 6 foot sections of footing on Monday, there is a 6' section between the 2 we dug out for this first wall. We'll hopscotch our way around and then excavate between and tie it all together. We are going down 2', hopefully you won't have to go too deep. We hit soft rock just below the surface so are using a percussion drill, basically a big honking hammer drill in hammer but not spin mode and chisel then shovel the dirt out. We have to over dig the trench width a bit to be able to get ourselves in there, we'll then form to correct width prior to pouring. Work slow and safe, we are a bug to a building.

For yours I think I would work a corner at a time and run 4-6 feet out of the corner in each direction at a time.

 

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