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Thread: Who knows?

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    Default Who knows?

    Who knows what I need to do with the stumps in the pad area of my cabin site? I plan to take off the overburden then put the pre cast pilings on some concrete pads. The whole support system will be above ground with no digging. What I need to know is since there are trees in the area I will be putting the cabin on do I need to dig the stumps out or can I just cut them off flush at the ground? None of my support pads will be directly on a stump but I wonder if, as they rot away, the ground will settle and effect my supports.

    Since you are all very detailed in your answers I will tell you that I have a good gravel base under the overburden so drainage is good. Any ideas on this answer or anything else I should consider with this system is appreciated.

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    Supporting Member iofthetaiga's Avatar
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    You can just flush cut the stumps. No need to remove them. But you should do a little digging so that your foundation pads are directly supported by the gravel subsoil. Placing your pads on the spongy organic layer will quickly become apparent as a critical error.
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    Quote Originally Posted by iofthetaiga View Post
    You can just flush cut the stumps. No need to remove them. But you should do a little digging so that your foundation pads are directly supported by the gravel subsoil. Placing your pads on the spongy organic layer will quickly become apparent as a critical error.
    Thanks, I should have been more clear that I am digging down to solid for the pads just not any deeper than good solid ground. Someone told me that if you don't remove all the organic layer for the entire pad site that you can have odor problems in the cabin. Any thoughts on this? I was thinking of removing it only in the areas the pads would sit.

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    Supporting Member iofthetaiga's Avatar
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    Quote Originally Posted by bawanna View Post
    Thanks, I should have been more clear that I am digging down to solid for the pads just not any deeper than good solid ground. Someone told me that if you don't remove all the organic layer for the entire pad site that you can have odor problems in the cabin. Any thoughts on this? I was thinking of removing it only in the areas the pads would sit.
    If you were to be building a gravel pad, constructed of fill material, and building atop that pad, then what that advice would hold true; you don't want an organic layer sandwiched underneath your fill pad, but for mechanical reasons, not reasons of odor. I've never heard of such a thing.

    What you propose is different, and if you do as you say you intend, you're on the right track. You'll still want to allow for adjustments in the future though, as even with well drained gravel substrate you are likely to get some movement over time. Plan your posts/piers/pilings such that you can re-level by jacking and shimming in the future.
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    Yes, I am planning on using the bases that have a threaded bar that goes up to the bracket that holds the beam. May get to the end of the travel on the threads at some point but should be able to back it off and shim so that I can make adjustments as more settling occurs. Any thoughts on the spacing of the piers on a 20x32 cabin?

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    Supporting Member iofthetaiga's Avatar
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    Quote Originally Posted by bawanna View Post
    Any thoughts on the spacing of the piers on a 20x32 cabin?
    Way too many variables to make a general statement about that. It depends on the load bearing capacity of the specific site soil, the weight of the structure, the design of the floor/foundation system, the size of the footer blocks or pads....
    ...he who knows nothing is nearer to truth than he whose mind is filled with falsehoods & errors. ~Thomas Jefferson
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    I tried that threaded bar thing on a small cabin. If you don't go really big, those things will bend if they get out of line any at all. Seen it in person.

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    Supporting Member iofthetaiga's Avatar
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    Quote Originally Posted by Redlander View Post
    I tried that threaded bar thing on a small cabin. If you don't go really big, those things will bend if they get out of line any at all. Seen it in person.
    I was going to mention that too, but... Those things aren't really made for supporting whole structures or significant loads. If it were me, I would pour a 20x20x6 concrete pad, and then drystack 8x16 concrete block to make 16x16 piers. Cap the pier with a plate of 3/4" treated plywood and place support beams on top of that.
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    I made heavy duty brackets with 1 1/8" all thread welded to 4" x 6" box tubing with one side cut off. use 3/16" wall tubing or the 4 X beam wont fit. any welding shop could make them for you.
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    I am no engineer but I am a general contractor that builds and there is no chance in hell I would put a house on all thread unless I had an engineering plan and stamp...

    they no only need to support a bunch of weight but also be able to absorb or resist shear from any sort of ground movement like an earthquake...just my opinion of course..

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    If I use the concrete blocks then put a treated plywood piece on top would I just use additional pieces of plywood on the piers as shims as settling occurs?

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    Quote Originally Posted by iofthetaiga View Post
    I was going to mention that too, but... Those things aren't really made for supporting whole structures or significant loads. If it were me, I would pour a 20x20x6 concrete pad, and then drystack 8x16 concrete block to make 16x16 piers. Cap the pier with a plate of 3/4" treated plywood and place support beams on top of that.
    If you use plywood plates, I'd recommend marine plywood !!! It fights delamination. Better, to me, would be solid wood plates, just as in the big leagues [e.g., house building], where wood is always used between the plate [or wall or beams/strringers] and concrete or masonry blocks. And remember: with freezes and thaws, the gound WILL move. Be prepared to jack the cabin up and re-shim, unless your pier pads go down below the known frost line. Frost travels horizontally, too, so the ground beneath your cabin will also freeze. You may have seen streams freeze from the bottom up during hard freezeswith little snow cover . . . . .

    iofthetiaga is right about the pads, though I'd make them a little deeper (10" maybe, with two 1/2" rebars each way at mid-depth. I'd dalso recommend using 16" concrete "column" blocks, since they're one-piece. A 2x wood plate [pressure-treated] will not close the openings in the concrete blocks, but they don't have to.

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    Quote Originally Posted by bawanna View Post
    If I use the concrete blocks then put a treated plywood piece on top would I just use additional pieces of plywood on the piers as shims as settling occurs?
    Once again - - - - - I'd stay clear of plywood at the pads/piers. But, what do I know ........................ ?

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