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Thread: Building an earthen Cabin

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    Default Building an earthen Cabin

    Hello to all the great people of Alaska. I am a new comer to the forum and I am looking for your help and expertise to build an off grid earthen type cabin on my remote property on the Kenai peninsula. I plan on building it in the ground below grade. The earthen walls will be 12" thick, floor 12" thick earthen roof 2' thick. I plan on using a concrete thermal break and foam board between my walls, floor and roof from the surrounding earth to stop energy loss back into the environment. I plan on using glacial silt for the earthen material. My hope is to have walls floor and ceiling that will be able to hold thermal energy in the thermal mass of the walls floor and ceiling thus reducing the energy requirements to heat the cabin. The area is free from perma frost (one less problem for construction and excavation). The interior dimensions I am looking at are 8' ceiling height, 16' wide x 30' long. It will be a 4 season cabin with wood heat, propane stove, solar & wind power for electrical needs with back up gen, composting toilet, well water via hand pump self draining.

    By the way the build location is 15 miles from the nearest road 30 miles from the nearest town. I look forward to all your comments finger pointing and laughter.

    Thanks in advance for all your help
    Rich Heipp

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    Moderator Daveinthebush's Avatar
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    My biggest question would be is that if you are 15 miles from the nearest road, how do you plan to get all the materials back in there?

    Next question would be; Have you done any excavations to determine or have knowledge of where the water table is?

    Have you researched any Alaskan homes to see if anyone else has tried this method anywhere else in Alaska? I have never seen any around and there might be a reason for that.

    I know that where I live I can't dig three feet down without hitting water.

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    Dave, I know there is two passive in ground homes in Anchorage and one in Ninilchik. This is very doable if one finds a site that is above the water table, of course the snow melt and annual rainfall also require the prevention of water intrusion to be spot on.


    Rich, what are your plans for ceiling support? How are you keeping water from intruding? You may already know but you will have to have quite the air transfer to keep your humidity level down, this is an issue in just about all partial or full subterranian homes and it will have to be in effect when you are not there.


    I have thought some of this out for myself and its on the want list some time in the future should I find a proper bit of property. I would want a hill to side excavate EPDM would be used as a water barrier. Thoughts are that my excavation would allow a set back as the wall height increases, should I have road access I would slip form an 8" concrete wall both sides of this would get sealed and the outside would get 2" rigid foam sprayed on and then the EPDM would wrap back over the top of the wall then the wall would be back filled half way up. If there is no road access I would use rail ties instead of concrete.

    The hard part is the roof/ceiling I plan on using steel beams and corrugated galvanized steel sheet covered in four inches of concrete that is sealed and covered with 2" of rigid foam sprayed on, then EPMD would be come down over the outside walls and be seam sealed. My one open end wall will be glass covered at some where between 60 and 70 degree's. Even with our cold winter temps on a sunny day no other heating source should be needed and a proper heat sink should radiate heat for a couple hours after the sun goes down. That should be about 4pm but with so much mass already at a good temp little auxillary heat should be needed.


    There is hours of talk on this subject but I need to get outside right now, look forward to more discussion

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    Oh if it ends up being off the road system, I plan on using my moose buggy in both summer and winter time to haul in the goods. A skandic would probably be on the shopping list also.

  5. #5

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    Radon is a real concern up here as well. I have seen twice where radon tests were conducted on the same houses and radon was not detected intially and then showed up later. A solid vapor barrier will slow it down and often stop it's intrusion, but it also traps moisture inside. The constant battle with venting would not be something I would want to deal with. I am a firm believer that a cabin needs to breathe, like a living organism to remain healthy.
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    Yes I test dug for the water table and no problem there. I plan on going up 12 miles of beach front to move in supplies and materials and just two miles inland from there to the property. The house will be dug into the side of a sloping hill. The roof supports will be 10x10 wood beams. I plan on using sand bags to build a bunker type structure. Once the unit is built I plan on supper heating the interior to eliminate exes moisture from the structure. The exterior will be moisture proof to help maintain minimum moisture levels inside.

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    My plan to get the materials in is to just use a four wheeler and trailer. I plan on cutting my own beams on sight out of white spruce with a chainsaw mill. The interior of the sand bag walls will be covered/finished with mud. to give it a modern appearance. I am thinking that the use of the wood stove will dry out the interior and the door and window seals will keep out the excess moisture.

    Hey guys keep it coming you guys are great.

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    Sorry to be a downer but I see many challenges ahead for you. You do realize the ground temp probably doesn't ever exceed 45 degrees even in summer. That means a cold cabin or heating year round. If you use glacial silt it is frost susceptible so if it ever freezes it will expand and heave your walls in. Just way to many down sides to be practical in Alaska, IMO. Maybe you know something I do not , I'd be interested to hear how it goes once you get it built. Good luck.

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    as to the radon gas. I am thinking that the use of the thermal break will eliminate the radon gas from entering the cabin and force the gas to go around the thermal break and through the surrounding soils. I do plan on having a drain tile system in place and floor drains.

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    After reading your last couple posts I see you've got this more planned out than appeared at first. Nonetheless, unless you feel the need to prove that it can be done, I think you'd be much happier with a conventional cabin that the sun shines on

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    I am taking in account the frost heave glacial silt soils. I plan on the interior silt soil walls to be dried out after construction. As you pointed out the silt around the cabin will expand and could push the walls inward (great point). I plan on using a natural expansion joint of clean stone. I do plan on building small test walls 6x6 squared to see the effects of a few winters prior to the build.

    Dam good point dkwaterhog

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    Some things to consider, I have filled my share of sandbags the number is in the high thousands and wether they are burlap or synthetic they breakdown to a point that after two or three years you can poke your little finger through them with little to no effort even if they are protected from sunlight. Super heating the interior will also hasten this breakdown.

    The excess moisture comes from you being in the structure it includes your breathing, cooking, clothes in winter or rainy days and just the general moisture that comes from warm humid air meeting cold outside air, windows or walls. You will still need a good air exchanger. Look into 12volt solar powered fans they are powered all by themselves and used in marine enviroments I have used one for seven years and it spins on even the most overcast days.

    Being this close to the beach using cement mix and beach gravel you can probably make some pretty stong concrete, it would be worth your time to do some testing with it only cost $6 in cement and some time on the beach. Google slip wall forming its an easy and quick way for a single guy or two to make concrete walls that are strong and cheap to do.

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    Quote Originally Posted by Rich Heipp View Post
    My plan to get the materials in is to just use a four wheeler and trailer. I plan on cutting my own beams on sight out of white spruce with a chainsaw mill. The interior of the sand bag walls will be covered/finished with mud. to give it a modern appearance. I am thinking that the use of the wood stove will dry out the interior and the door and window seals will keep out the excess moisture.

    Hey guys keep it coming you guys are great.

    Do you plan on using cob as your interior mud? Is there alot of clay in your area? if its glacial clay this will not work for your interior covering. Your going to need a more durable wall covering up here our natural building materials just are not suited for most of the southern "green" building methods.

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    Moisture and cold temps are the two major hurdles here. I have studied of earthen homes in many different climates and geographic locations. Alaska will surly be a true test of this type of construction.

    please keep the constructive criticism coming I need all I can get

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    I planned on mixing dry Portland cement with the silt then bagging it then compacting the bags in place as they are layered. I planned on using a plaster mud for the interior walls reinforced with wire mesh to bond to and to grab to the walls. This should eliminate the concern of the bags degrading over time.

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    rdrash
    Your point on the moisture is valid and the air exchangers are a must, your expertise is welcome. You have my full attention

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    Can anyone give me the pros and cons on the composting toilets? do they really work? Do they smell up the cabin?

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    When you say sandbags are you talking about regular sandbags or the specific earth bags being used to build homes in the south west? I am pretty sure that while more money the other bags have a stabiliser in the just for long term use. A solar batch water heater that has a heat exchanger inside your dwelling would probably be enough if built right to keep inside above freezing all winter long with no other aux. heat. Somthing to consider if your not going to be present full time.


    Another question, have you googled or researched the term "earthship"?


    Think like this but on a smaller scale not meant to be your primary heat but a cheap way to have hot water and keep things above freezing inside
    http://www.builditsolar.com/Projects.../solarshed.htm



    The full site here has many items that may prove useful in your homesite on the penninsula

    http://www.builditsolar.com/Projects/Projects.htm

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    Quote Originally Posted by Rich Heipp View Post
    Can anyone give me the pros and cons on the composting toilets? do they really work? Do they smell up the cabin?
    My friend Mike Haywards parents have used one since 1996 you do have small bags that need disposed of. They can be incinerated.

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    I know nothing of this type of building, and I may not even get the whole picture of what your doing, but would logs stacked on the inside of your walls (kinda like building a log cabin on the inside) help with the warmth and help support the walls when they heave?
    Eccleasties 8:11 Because the sentence against an evil deed is not executed quickly, There for the hearts of the sons of men among them are given fully to do evil.

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