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Thread: Cribwork Foundation

  1. #1

    Default Cribwork Foundation

    Hello,

    I am going to be building a cabin this winter and all my research pointed to building on cribwork. I bought railroad ties and cut them up into 4' sections and treated the cut ends.
    Cabin size: 24'X24'
    Cribwork: 5 railroad ties high. 3 on the bottom layer and 3 on the top layer and 9 total stacks
    Beam: 4X12X12 spliced together to make 3 main beams 4x1x24

    Should I pound rebar through the cribwork to stabilize it? Some say yes and some say no.
    Attatch main beams to crib work with angle iron?
    Ideas on how to shim for settling? Cedar shims?
    I bought 6 of the DB-138DB1 duckbills to pound in the ground and attach on the ends of the 3 main beams.

    Here is a rough draft picture with the ties 24' apart in only one directions and missing the bottom layer of 3. Any advice would be apprecitated.

  2. #2
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    Need more info - whats the ground like (that pictured?), 1 story/2 story, exposure to wind, flooding? Weekend cabin or full time?

  3. #3

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    It's Lakefront and lot has a mix of larger birch and spruce on it with alders. I have been told by neighbors that it is somewhat damp soil, not swamp but pretty moist. Others have had problems with frost jacking with post foundations. I haven't seen it in the summer yet but will be flying in mid June. It will mostly be a weekend cabin. It will be 24'X24' with a 4' pony wall and loft upstairs. I think I'll be high enough to avoid any flood issues and figure I'll be at least 8' above the Lake water level or more. I figured the duckbill anchors will handle any wind issues. It's pretty heavily treed around the lake area.

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    Here are a couple pix of the actual lot:


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    Member Dirtofak's Avatar
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    You can save a bit of money be going 20X28. Longer materials cost more, are harder to freight and heavier.

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    Member greythorn3's Avatar
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    save even more going 4 'x 8' anything fitting on a sheet a plywood would be cheap.
    Semper Fi!

  7. #7

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    Laid down typar and covered with the best gravel/sand/clay mix I could find:





  8. #8

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    It looks like the 4 x 12 is being supported by 3 adjustable threaded brackets. If this the way it is that will make for a very unstable cabin. That would have the cabin supported by 9 bolts .It would not be very strong laterally????

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    Member Dirtofak's Avatar
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    Quote Originally Posted by Big Bend View Post
    It looks like the 4 x 12 is being supported by 3 adjustable threaded brackets. If this the way it is that will make for a very unstable cabin. That would have the cabin supported by 9 bolts .It would not be very strong laterally????
    I haven't checked span tables but when I built mine I never spanned more than 7 feet.
    I don't mean to sound bitter, cold, or cruel, but I am, so that's how it comes out.
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    interesting for sure.. Did you have those brackets engineered for the weight they are supporting.

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    Member akriverunner's Avatar
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    i think i would have went a different route, did you dig any test holes with that mini ex while you were doing the dirt work? i wonder what the ground is like 4-6' down? maybe sauna tubes or pilings would be better. what area is this?

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    Member kodiakrain's Avatar
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    Not sure why people would say,"Not," to Rebar Pinning those together,...??

    I sure would, hope it's not too late, to still pull that off, but I would even consider drill and tapping 1" dowels down through those
    It just doesn't look solid enough, to my eye
    not even considering the threaded brackets yet,

    but ya gotta think even, "Mild Earthquake," I can't imagine those ties sticking together
    Wouldn't be hard to Pin them together, would make a Heck of a Difference, I think anyway
    Ten Hours in that little raft off the AK peninsula, blowin' NW 60, in November.... "the Power of Life and Death is in the Tongue," and Yes, God is Good !

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    Member 4merguide's Avatar
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    Quote Originally Posted by Big Bend View Post
    It looks like the 4 x 12 is being supported by 3 adjustable threaded brackets. If this the way it is that will make for a very unstable cabin. That would have the cabin supported by 9 bolts .It would not be very strong laterally????
    I totally agree.....
    Sheep hunting...... the pain goes away, but the stupidity remains...!!!

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    Supporting Member iofthetaiga's Avatar
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    +1 to pinning the cribbing together.

    As far as allowing the 9 screws to support the structure unassisted, I wouldn't. They'll be very handy for re-leveling when necessary, but I would shim up tight with smaller cribbing, taking the load off the screws, so that each beam is firmly supported in two places on each crib. Toenail your shim cribbing in place so it stays put, but can easily be removed/adjusted over time.

    I would expect that ground is going to move some on you. It looks like you've done a good job of setting yourself up for success with the gravel fill over typar, and the crib foundation was a good choice. Just make sure the beams are well supported across the top of each crib, taking the load off the screw jacks. That way your beams are rock solid and stable, your cribs are bearing load evenly, and your max beam span is reduced to the distance between cribs, which looks to be about 5 feet. Set yourself up this way and you'll be pretty bomb proof.
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    Member kodiakrain's Avatar
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    Quote Originally Posted by iofthetaiga View Post
    ,..... but I would shim up tight with smaller cribbing, taking the load off the screws, so that each beam is firmly supported in two places on each crib. Toenail your shim cribbing in place so it stays put, but can easily be removed/adjusted over time.

    I would expect that ground is going to move some on you. It looks like you've done a good job of setting yourself up for success with the gravel fill over typar, and the crib foundation was a good choice. Just make sure the beams are well supported across the top of each crib, taking the load off the screw jacks, and you should be pretty bomb-proof.
    Interesting note, as I'm reading what Taiga is saying,...
    I'm realizing that your crib foundation idea,...is exactly what they do in the Shipyards here in Kodiak
    for even pretty large boats,...
    it's all about the shim wedges driven in hard to tighten it all up,...
    and I've been working up on a boat in some fair size earth Tremblors,...and major Wind Gusts,...
    seems the boats are teetering up there, with only one crib setup under each side,...
    They never fall though,...

    Hmmm, just thinking about it all, late at night,...as I imagine 375matt, already has,...
    I'd still pin those puppies together tho

    but there must be some sheer strength factor with all those small surfaces interacting,...
    (more engineering than I'm capable of comprehending,...)
    Ten Hours in that little raft off the AK peninsula, blowin' NW 60, in November.... "the Power of Life and Death is in the Tongue," and Yes, God is Good !

  16. #16
    Supporting Member iofthetaiga's Avatar
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    Quote Originally Posted by kodiakrain View Post
    Interesting note, as I'm reading what Taiga is saying,...
    I'm realizing that your crib foundation idea,...is exactly what they do in the Shipyards here in Kodiak
    for even pretty large boats,...
    In this situation, you don't have to drive wedges because the load is completely perpendicular to the ground and you have the luxury of the screw jacks in place. Once your joist/beam structure is square and level and beginning to acquire load, determine the proper sized finish cribbing and install it by jacking with the screw, inserting the finish cribbing in place, and lowering the screw a bit thus taking the load off the screw and transferring it to the crib. No wedge driving necessary. Easy peasy.
    ...he who knows nothing is nearer to truth than he whose mind is filled with falsehoods & errors. ~Thomas Jefferson
    I would rather have a mind opened by wonder than one closed by belief. ~Gerry Spence
    The last thing Alaska needs is another bigot. ~member Catch It
    #Resist

  17. #17

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    I had to leave so the foundation is by no means completed.

    The screw jacks are 1-3/8" scaffold jacks I welded up in my garage but they are actually engineered to take around 10,000 lbs (maybe 16,000 lbs? can't remember but it was more than I needed) each at least before I started welding. They are just to get my beams set and level then I will crib up to them on each side as iofthetaiga said and the span will be less than 5'. The cabin is 24' and the cribs are 4' and I have 6" I held the cribs in so he was close with the 5' estimate.

    I have 2"x1/8" angle iron that I am going to lag bolt into the 4 outer corners of each crib tying them together.

    The 2 cabins next to me tried post and piers and one was done by a pretty popular cabin builder. One fell off the posts and sits on the ground and the other had to go to cribwork and the posts were at a 30 degree angle. The soil has anywhere from 4' to 8' of peat. It will not support the sideloads and they all tend to lean towards the lake. I just figured I would skip all the post stuff that doesn't work and go straight to what does working and do it the best I can.

    I am planning on it moviing. I would be shocked it if didn't. If for some reason it all does go to hell and fall on the ground at least I'll be in the same position as my neighbors!!!

  18. #18

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    Thanks for all the ideas too... That's why I put these pictures up in hopes of getting some advice so I don't have to go back and redo it. I don't exactly have a step by step manual in my hands to do this! As soon as the beams are set there are lots of manuals for that portion.

  19. #19

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    Does anyone know any good framers looking for work? I plan on starting to build the floor in a week and just keep going solo if needed.

  20. #20

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    some of the foundations at the Kennicott mine are cribs like yours. They are filled with gravel. That building is many stories tall.

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