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Thread: Another Remote Cabin Foundation Question

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    Default Another Remote Cabin Foundation Question

    I have read through the threads on here about remote foundations and wanted some more feedback on my project which will be moving forward pretty quickly. I have land in the Talkeetna area. The soil is sandy gravel with no rock in sight. I will be building a 20x20 one level 3 sided log cabin. I have heard from people in the area that the soil will heave. It seems I could dig below frost level and use sonotubes, but I have heard that even those will jack especially in an unheated building.

    My thought is to remove the organics and get to the undisturbed soil and pour some 2'x2'x8'' concrete pads and then build some metal posts that I put on the concrete pads which can be adjusted. I would use steel I beams on top of the posts and then conventional construction from there on up. I figured the building may move but I can adjust pretty easily to deal with the movement. Will putting some foam insulation underneath the pads help prevent the movement. Also, I have been told that if I want to use the system I described above, I would be better using the pressure treated wood instead of the concrete because the frost grabs the concrete and will not grab the pressure treated wood.

    Any thoughts. I don't mind hauling in 50-60 bags of sacrete to pour pads but hauling in enough concrete to go below the frost line is too big a project.

  2. #2

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    Quote Originally Posted by alaskamike View Post
    I have read through the threads on here about remote foundations and wanted some more feedback on my project which will be moving forward pretty quickly. I have land in the Talkeetna area. The soil is sandy gravel with no rock in sight. I will be building a 20x20 one level 3 sided log cabin. I have heard from people in the area that the soil will heave. It seems I could dig below frost level and use sonotubes, but I have heard that even those will jack especially in an unheated building.

    My thought is to remove the organics and get to the undisturbed soil and pour some 2'x2'x8'' concrete pads and then build some metal posts that I put on the concrete pads which can be adjusted. I would use steel I beams on top of the posts and then conventional construction from there on up. I figured the building may move but I can adjust pretty easily to deal with the movement. Will putting some foam insulation underneath the pads help prevent the movement. Also, I have been told that if I want to use the system I described above, I would be better using the pressure treated wood instead of the concrete because the frost grabs the concrete and will not grab the pressure treated wood.

    Any thoughts. I don't mind hauling in 50-60 bags of sacrete to pour pads but hauling in enough concrete to go below the frost line is too big a project.
    Ever thought about building on top of tree stumps? I have heard of guys doing this. Never seen it done, but I don't see why it can't be done on a remote cabin. I don't mean to hijack your thread here, but just curious about it myself. I am considering buying some remote land and I have been thinking about doing this myself. The only thing bad I have heard about it is that the stumps eventually rot. But I suppose you could possibly treat the stumps with some type of preservative. I have used a natural preservative before on garden boxes I have built for my wife. I think the recommended natural preservative is called copper brown or something like that. Has anybody heard of using stumps for a foundation before? And if so, is there anyway to preserve the stumps to prevent rotting?

  3. #3

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    A couple of points. 1_ The foam under the pads will do nothing to protect from them jacking as the frost will be under that also.2_ Yes the frost will grab the treated material just like concrete. The trick if you use the treated timbers is to wrap the in several layers of heavy black plastic and that will allow the plastic to slip against its self.3_ The part about the unheated building will have no effect on the frost jacking the supports. The best would be to dig down and put in Big Foot footings and then use either the treated post or the sona tubes if you are down below frost line you should be all right. Put your organics off to the side and after you are done with the post system then you could put that back in place in the area under the cabin and with the snow around the edges it would help with the insulation of the ground. If you are going to use the steel beams for support then install steel saddles on top of the post you can put a couple of peices of 1/2" steel under the beams and in the saddle in case one has to come down to keep things leval over the years. You could put one bolt through the saddle and the beam to make sure that you had no latteral movement. You would not need that in every post. Good Luck

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    Quote Originally Posted by alaskamike View Post
    I have read through the threads on here about remote foundations and wanted some more feedback on my project which will be moving forward pretty quickly. I have land in the Talkeetna area. The soil is sandy gravel with no rock in sight. I will be building a 20x20 one level 3 sided log cabin. I have heard from people in the area that the soil will heave. It seems I could dig below frost level and use sonotubes, but I have heard that even those will jack especially in an unheated building.

    My thought is to remove the organics and get to the undisturbed soil and pour some 2'x2'x8'' concrete pads and then build some metal posts that I put on the concrete pads which can be adjusted. I would use steel I beams on top of the posts and then conventional construction from there on up. I figured the building may move but I can adjust pretty easily to deal with the movement. Will putting some foam insulation underneath the pads help prevent the movement. Also, I have been told that if I want to use the system I described above, I would be better using the pressure treated wood instead of the concrete because the frost grabs the concrete and will not grab the pressure treated wood.

    Any thoughts. I don't mind hauling in 50-60 bags of sacrete to pour pads but hauling in enough concrete to go below the frost line is too big a project.
    Ice adheres to CEA's utility poles at 30# per square inch. I would think it will adhere to pressure treated wood as well.

    You only need enough concrete for the pads themselves. It would go into the bottom of the hole you dig for them. If you want a permanent installation, place the bottoms of the pads below the known frost line and make the piers ofo 8x8x8 concrete blocks with 2-number 4 (1/2") rebars vertically in each block pier. The top should receive a 2x wood plate. If you place the pads on the earth, they WILL heave with the freeze/thaw of the earth beneath. Frost will travel horizontally underground, by the way, and that includes through the earth beneath your cabin.

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    Quote Originally Posted by Bushwhack Jack View Post
    Ever thought about building on top of tree stumps? I have heard of guys doing this. Never seen it done, but I don't see why it can't be done on a remote cabin. I don't mean to hijack your thread here, but just curious about it myself. I am considering buying some remote land and I have been thinking about doing this myself. The only thing bad I have heard about it is that the stumps eventually rot. But I suppose you could possibly treat the stumps with some type of preservative. I have used a natural preservative before on garden boxes I have built for my wife. I think the recommended natural preservative is called copper brown or something like that. Has anybody heard of using stumps for a foundation before? And if so, is there anyway to preserve the stumps to prevent rotting?
    You're right about the copper brown, but the stumps will rot out beneath the surface of the earth, too. You won't be able to stop that. Copper brown is usually reserved for sawed limbs, though it would work on freshly cut stumps.

  6. #6

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    Quote Originally Posted by Grizzly 2 View Post
    You're right about the copper brown, but the stumps will rot out beneath the surface of the earth, too. You won't be able to stop that. Copper brown is usually reserved for sawed limbs, though it would work on freshly cut stumps.
    Good point. I was thinking the same thing. I am wondering though, how long does it take for the roots of trees to rot underneath the ground? 10 yrs, 20 yrs, 50 yrs, 100 yrs? If the stumps can last a long enough time by preserving them aboveground, why not? I have heard of guys doing this. Anybody know how it works?

  7. #7

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    It is not a good idea to use tree stumps for a cabin support several reasons one that you would be hard pressed to get the proper placement for the correct support another is that they would no all rot at the same rate and it is a lot more work trying to replace supports under a cabin than doing it right in the first place.There is all types of wood destroying beetle's and such that could very well migrate into the building from the stumps. There is a saying that sometimes the longest route is most of the time the fastest. When you try short cuts most likely you will get a chance to redo the job.

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    Quote Originally Posted by Big Bend View Post
    It is not a good idea to use tree stumps for a cabin support several reasons one that you would be hard pressed to get the proper placement for the correct support another is that they would no all rot at the same rate and it is a lot more work trying to replace supports under a cabin than doing it right in the first place.There is all types of wood destroying beetle's and such that could very well migrate into the building from the stumps. There is a saying that sometimes the longest route is most of the time the fastest. When you try short cuts most likely you will get a chance to redo the job.
    Very good points. Not to mention carpenter ants and such. I know what your saying about the proper placement. That was something I was thinking was a going to be a problem. I know a guy who apparently owns several remote cabins and supposedly does it this way. I guess he isn't too concerned with the long term value of his cabins. The bad thing is he is a general contractor. He is a nice guy, but this probably isn't the best practice.

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    Quote Originally Posted by Bushwhack Jack View Post
    Good point. I was thinking the same thing. I am wondering though, how long does it take for the roots of trees to rot underneath the ground? 10 yrs, 20 yrs, 50 yrs, 100 yrs? If the stumps can last a long enough time by preserving them aboveground, why not? I have heard of guys doing this. Anybody know how it works?
    The only way I would use tree stumps is if they were petrified ones!
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    Quote Originally Posted by alaskamike View Post
    I have read through the threads on here about remote foundations and wanted some more feedback on my project which will be moving forward pretty quickly. I have land in the Talkeetna area. The soil is sandy gravel with no rock in sight. I will be building a 20x20 one level 3 sided log cabin. I have heard from people in the area that the soil will heave. It seems I could dig below frost level and use sonotubes, but I have heard that even those will jack especially in an unheated building.

    My thought is to remove the organics and get to the undisturbed soil and pour some 2'x2'x8'' concrete pads and then build some metal posts that I put on the concrete pads which can be adjusted. I would use steel I beams on top of the posts and then conventional construction from there on up. I figured the building may move but I can adjust pretty easily to deal with the movement. Will putting some foam insulation underneath the pads help prevent the movement. Also, I have been told that if I want to use the system I described above, I would be better using the pressure treated wood instead of the concrete because the frost grabs the concrete and will not grab the pressure treated wood.

    Any thoughts. I don't mind hauling in 50-60 bags of sacrete to pour pads but hauling in enough concrete to go below the frost line is too big a project.
    You're on the right track Mike, and Big Bend's advise is sound. Make sure you get through the organic layer and pour your pads on mineral soil. Your steel post idea will work fine. Stacked concrete block is commonly used for piers as well and works great. I-beam stringers are a great way to go, if you can afford them and have the ability to get them in place. Depending on the economy, steel I-beams are sometimes actually more cost effective than equivalent wood beams, make a great foundation. Take Big Bend's advice to heart, if you intend to 'plant' any type of pier or post below ground level, regardless of it's material composition, and wrap it in a few layers of good poly. That will prevent the freezing soil from getting a grip on the post and jacking it out of the ground, which is 'frost jacking' (not to be confused with frost heaving which is different). It sounds like you're going to stay completely above grade though, which is best, and eliminates any need to worry about frost jacking. You will get some frost heave regardless, and that's the point of your chosen foundation type; you'll be able to jack and shim to re-level if the ground shifts slightly underneath you over time. Don't put foam board or anything else under your footer pads, and forget the tree stump idea.

    PS edit: If you're going to go to the trouble to remove all the organic layer from the entire 20x20 area, as opposed to just where you need to place footer pads, I would NOT return it to the area underneath the cabin. The amount of R-value it would provide to the ground is of no consequence and you're going to get some heave regardless. Having the entire area clean to mineral soil will give you a cleaner environment for storage under the cabin. Additionally, having no organics underneath your structure makes it easier to defend from wildfire as well.
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    quote "Having the entire area clean to mineral soil will give you a cleaner environment for storage under the cabin. Additionally, having no organics underneath your structure makes it easier to defend from wildfire as well. "end quote
    And probably a nice place for water to collect.
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    Quote Originally Posted by Music Man View Post
    quote "Having the entire area clean to mineral soil will give you a cleaner environment for storage under the cabin. Additionally, having no organics underneath your structure makes it easier to defend from wildfire as well. "end quote
    And probably a nice place for water to collect.
    Hmmm. Yeah, I suppose that's possible, if a guy was to choose to build his cabin in a depression. I have always elected to build my structures on a spot that will drain away from the structure. To each his own I guess.
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    If I were worried about any heave, after doing all you can to get below frost line, I would put a 1 1/2 piece of abs in the center of your sonotube x 14"(you will also have rebar hoops I am thinking.)I would make some 3-3/4" x 6" long, 5"" deep. saddles with 3/8 plate on the bottom, with 1-1/4 Construction "Coil rod" cut and welded in the center.The coil would have a nut on one end for a better weld to the saddle.Then I would install a 1/2 x 4 x4 steel plate on your concrete pier with a 1-1/2" hole centered.Now, just install a she bolt nut on the coil, and install your saddle to the abs pipe.Shoot them all level, and if in a year, you have any problems, you have many inches of adjustment.

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    The trick with stumps is keep them alive,don't kill the tree. Keep 3/4's of the cambium layer alive and your good to go. Just keep the tree pruned to keep the cabin safe. Think notches insted of stumps.
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    If you use stumps as a foundation, you deserve what you get. Stumps rot out at a much faster rate than pressure treated lumber.

    Since you are in the Talkeetna area go see AKDoug.
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    How on earth would you be able to get down past the frost line with manual tools? How far is the frost line around talkeetna? If you just used post hole augers and went down 36" how much actual frost heave would you even get. I have seen a few cabins just sitting on concrete blocks with screw plates for level adjustments, if they work why wouldn't 36" work using a post hole digger.

    What are your guy's suggestions if tree stumps wouldn't work? and you couldn't bring in heavy machinery for auguring holes with big footers at the bottom. Hand tools only and done in a couple days, how would you do it. (gas powered tools big enough to fit in a 14' jon boat will suffice as hand tools.)

    Joe

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    My brother welded up a sleeve and plate to fit on a jumping jack compactor.

    Just take a bifold ladder, jumping jack, and 8' x 4" drill stem. It takes about a minute per foot in heavy clay/gravel.
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    you have intrigued me, do you have pictures of this contraption? what is a sleeve and plate on a jumping jack compactor. Sounds like one heck of a machine.

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    Quote Originally Posted by jojomoose View Post
    How on earth would you be able to get down past the frost line with manual tools? How far is the frost line around talkeetna? If you just used post hole augers and went down 36" how much actual frost heave would you even get. I have seen a few cabins just sitting on concrete blocks with screw plates for level adjustments, if they work why wouldn't 36" work using a post hole digger.

    What are your guy's suggestions if tree stumps wouldn't work? and you couldn't bring in heavy machinery for auguring holes with big footers at the bottom. Hand tools only and done in a couple days, how would you do it. (gas powered tools big enough to fit in a 14' jon boat will suffice as hand tools.)

    Joe
    Concrete block piers work very well, as do piers made of treated cribbing, and one of those options would be my choice. I wouldn't put posts in the ground for a small cabin/house. All that buys you is a lot of labor up front, and problems with frost jacking down the road. More pros than cons with the pier on pad option; more cons than pros with the post option.
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    Quote Originally Posted by jojomoose View Post
    you have intrigued me, do you have pictures of this contraption? what is a sleeve and plate on a jumping jack compactor. Sounds like one heck of a machine.
    This is a jumping jack compactor

    http://www.gertens.com/cart/catalog/...92/image/3306/

    The shoe comes off, and weld a 6" length of pipe onto it, which fits over the 4" drill stem.

    I don't have a picture of the whole set up.
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