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Raw Earth Walls? (Pure dugout house?)  RSS feed

 
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So, I've been considering houses a lot lately....and was wondering why a pure dugout house wouldn't work?

Basically

1) Dig a hole and entrance and remove top soil from the area while creating a slop away from the top of the pit, starting a couple feet out from the hole (making sure the location has adequate drainage and is above the ground water of your area)

2) Cover the ground with gravel (sloped to allow any excess water to drain to the front...continue this drainage channel as far as needed to allow for the area to drain)

3) Put thick beams across the top, overlapping far onto each side of the hole onto the raw ground

4) Cover with some dirt at a slope

5) Cover the hole and the surrounding area with a pond liner (the pond liner should stretch 6+ feet away from your open space, and terminate as far down slope as possible at a drainage channel)

6) Create a drainage channel with loose rock where the pond cover ends (digging down several feet further)

7) Cover the pond liner with loose gravel, then sand, then dirt (end result, it should be sloping to allow water to shed off)
     7a) ((Optional)) Create a layer of sodium bentonite clay on top of the pond liner as a first defense, creating a water barrier redundancy


And then you can take it however you want....putting in supports in the raw earth walls and covering it with some lime plaster, putting in a floor, creating vents up and through the pond liner (or under it and exit elsewhere).

The idea is essentially controlling the moisture from the entire area of the house, and not just directly over you. This ensures the ground dries out and stays dry....stabilizing the conditions to serve as reliable structural material to support the roof.

It also brings down the cost (and complexity / labor) of construction....requiring just digging equipment, logs, and a pond liner.

I have to be missing something, why aren't people using the raw earth to create with? Dugouts, pithouses, whatever you call them these types of houses were some of the first ones people used.

With modern digging tools a single person could dig out a small cottage sized home in less than a day....cover it with the structural roof the next day....and on the 3rd day have the liner and soil on top...and the 4th + 5th day dig a big trench around everything with gravel. And that is just the first week....

 
pollinator
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I have no personal experience with a dugout house (aka - pit house), but from what I've read in diaries from the late 1800's USA, pit houses were dark and damp. If you could adequately address those problems, then a pit house is an option for the right situation. Also a problem in the 1800s was that the roof logs and lumber would rot, thus caving in after time.

With modern knowledge and technology, those problems should be able to be overcome. Now you'd only need the right site. Where I'm located, pit homes would not be viable, though we do have people who live in lava tubes under ground. It's not legal, but it's done anyway.
 
Bob Bobserson
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Yea, they had to deal with their moisture head on....directly with raw materials. So there was only so much they could do to protect the house (let alone the area) from water.

But today we have pond liners or layers of sodium bentonite clay (though I would be really nervous relying on the clay alone, since roots can grow through it) to create strong layers to resist the moisture from coming through. Once you remove the moisture from the soil, you remove the issue of soil to wood contact causing rotting ....and remove moisture entering the house from the surrounding soil (which is why current methods for basements often fail, since they are trying to stop the moisture directly at the point of entry into the house with a material that often cracks).

Natural lighting would be more of a problem (especially if the house extends further out from the entrance). I guess you could install solar tubes.

It just seems like suchhhhh a cheap alternative to getting a small house made.
 
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Think Cave, that's what you would be dealing with moisture wise, lots of seeping.

The pond liner might work.
 
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I have actually studied this idea as well as build two test holes. Once caved in one spring when we had a freakishly log heavy downpour. We have super hard clay soil. The other got fleas and was unhealthy most of the year.

Will It work?  It depends... LOL

Fleas, Floods, and Muds..  Unless you live in a VERY dry area you will have moisture problems. Not to mention potential pest problems.  Digging into the side of a hill can work.
The best compromise I have found is a buried structure above ground.  You should still design it like a house with a roof that is sloped and moves water away.  A drain channel in the floor around the walls is a good idea too. You could build it earthShip style or "$50 and up underground house"' style.

As for comfort... That also depends.. On rain, average temperatures in your area, your comfort level. A rocket stove mass bed/bench heater can easily take care of winter by warming your body instead of air. 

You really have to decide what you are desiring here. If the price is the issue, I could show you how to build a darn-near-free house that is actually very warm in the winter and very cool in the summer.   If hiding is the issue a quonset hut burried is great IF you also insulate.  If living secretly on land you don't own is the issue, just fast claim some federal land or build the ultra-low cost house expecting it to be lost. 

Anyway, give some more details. What is our purpose, what are your short and long-term goals ect..
 
Bob Bobserson
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Oh great to hear from someone that has tried out some dugouts!

I'm curious what lengths you went through to manage your water around the area? A cave in is pretty catastrophic (which is why I was thinking managing the moisture and water flows in the area would be key to making sure the soil around the home isn't destabilized).

How was the other one unhealthy? (besides fleas) My thought was that with proper ventilation and dry soil, the interior space would be dry and livable like any structure (other than less windows).

I thought a bit about a buried structure, but it seems like that is a more expensive building (in time, labor, cost). Maybe creating your own raw earth walls by just piling up some large berms to frame the house? But I would worry that it wouldn't be compressed enough to really offer any substantial structural benefit (so you would have to get in some heavy machinery to stabilize it)....UNLESS you constructed them with mechanical reinforcement or chemical reinforcement ....but, then it gets more complex and I don't know how long it would really last before it became unstable.

Personally my goals aren't about trying to squat on someone elses land or hide....it is just a faster / cheaper construction method that seems like it would produce a decent housing base. Then you could expand upon it with proper plumbing and additional rooms and basically whatever else you are looking for.

If it worked, it would be a great boon to others looking to create a natural home (even being able to do it themselves in a reasonable amount of time). That would make this option of living available to more people.
 
Su Ba
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Not knowing your location, it's difficult to be more helpful. But you may wish to look into the underground living community in the Australian opal fields.
 
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Hello,
It looks like you've given this idea a lot of thought which is a good sign of success if you want to try it.  The others are correct, location and understanding soil conditions are the key to getting this right.  My great grandfather did something like this and believe it or not, it was still pretty cozy 20 years after his death without any maintenance. 

Here are a few reasons why you don't see this much:
1) Building codes.  Sites vary so much that you would have to run a few tests and have things engineered per site.  Inspectors don't know what to do with non-standard things.  This also hurts financing.  Even a normally reinforced concrete bunker would be almost impossible to get financed.
2) Egress.  You're going to have to put in openings and wells so that people can escape in case of fire.  This will thwart some of the water proofing.
3) Insulation.  You're going to need to put in at least R-40 in your walls with rigid foam board to prevent condensation and mold since the walls will be cooler than the dew point sometimes.  This is expensive.
4) Radon.  You're either going to get cancer from the sun or the dirt haha!  Most places will have radon build up if you don't make a way to vent it.

Still your idea is sound and will work in practice with proper planning and attention to detail.
I think you should have a minimum slope of 10% (1' drop per 10' horizontal feet) for your roof, and I think 10' rather than 6' for the liner overhang.
You should make sure the soil isn't backfill and filled with all sorts of organic crap.  A nice consistent native soil with a lot of clay would be ideal.  Some soils I've seen will never make a dry hole and have something like shear planes where water drains.  My great grandfather's place was in North Carolina and had an almost green soil like Baldassare Forestiere had in California.  It wasn't damp by any means, but not perfectly dry either.  When struck with a pick-axe it absorbed the blow and maybe went in 1/2".  You shouldn't have a vertical cut in the soil more than 5' without sloping it and I wouldn't bother benching it.  A lot of people die from excavations.  Keep an eye out for fissures in the soil near the edge of the hole.

What kind of floor did you have in mind?  You should definitely install a sump pit with pump.  Even better would be a drain that's at 2% that used gravity.  This could even be a way to let the radon out.  Sealing the walls and floors will be critical to keep pests out.  As Dan said, fleas were an issue.  I was building out a hospital once, and we had a long period of heavy rain.  There was a 2 year old tunnel in another area that filled with termites.  This tunnel was built well and didn't flood.  All the surfaces were cast in place and clean.  All of those termites came through a 1/4" hole between the slab and wall!   
 
Bob Bobserson
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Humm, glad to hear someone has tried something similar and it worked out ok!

I've been thinking about the problems you mentioned and researching a bit.

1) Building codes - This is just a big problem in general. The cost of construction is so low that financing of the structure shouldn't be a huge challenge....but getting it approved by the local government is. I guess it comes down to how open your government is to natural building.

2) Egress - This is why I am paranoid about trying to cut through the pond liner or other barriers above. Vents and other things like that would need to be extra extra sealed. Just something to watch out for carefully.

3) Insulation - I wonder if there is another way around expensive insulation (or alternative insulation). Mold is less of a problem if you lime wash...but still condensation on the walls is not a good situation (though if you manage humidity levels with good ventilation and even a desiccant....I wonder if you could get away with it?)

4) Radon - Yea, just something to watch out for. Good ventilation is step 1 (along with moisture)


Yea, a good roof slope is important to shed off the rain water or snow....and then another good slope where the pond liner is (I was imagining soil on top of the ceiling supports...and then the pond liner, then on top of that soil / gravel / sand for a green roof at a decent slope to shed off water.

For cutting deep enough for a full floor, I wonder if a slope of the soil walls would work. Then you would have a little extra space towards the top of the wall to run other things? Perhaps a pipe for ventilation or even heating around the perimeter? Hmmmmm, I could see designing this as a feature. I've seen some stone stoves that had extra channels in it to heat up a thermal mass , forcing the flow of heat to run along a convoluted pathway......doing the same thing around the house might be interesting, while also using the dry heated air from the fire to pull out moisture. The cost of fire bricks to create channels doesn't seem that substantial)

Anyhow, floor wise the idea was another drainage opportunity leading away from the house. Since you have to get in from one side to dig the thing anyway, why not dig a little deeper and throw in gravel / sand / stone ....then on top compress dirt and finish it off however you want. Pump would be good if you are digging straight down on flat land, but ideally you would be on a hill or some other raised position (even if you create it) to make drainage channels way easier.

Termites from what I hear are more of a problem if you have moist soil? But since the entire area is protected from moisture before it gets anywhere near your living area, I would think everything would dry out enough to stop it from being an organic active zone. 
 
pollinator
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If you used Engineered Soil, which is just a fancy term for using geotextile fabric to stop the sheer forces on soil, and compact it as you shovel it out, and place it beside the dugout house, you should be fine as far as slump (collapse) goes on the walls. Roads use this all the time for approaches to bridges and such.

As for the dug out home itself, they were used a lot by the Irish during the potatoes famine when they were kicked off their rented farms and had to subsist. In that case, they dug a hole into the hillside, but they REQUIRED a fire to dry out the moisture in the soil, and to provide heat since a dug out home would be cool from the temperature of the earth being below that of what a human prefers (70 degrees). In the case of the Irish, they were literally so starved, they lacked the energy to go out and gather wood, and thus a lack of fire allowed the roofs above to slump and cave in, often killing the families. Dire times indeed. Obviously with an ample supply of wood, and modern food sources and woodstoves, this would not be a problem.

In my class on sheep farming, I do a scale model of a dug out barn just as you describe, making it in about 10 minutes in front of the class so they can see, a sheep farm with little cost is going to be profitable. A dug out (or earth formed barn above ground) is a great way to build a cheap barn fast.
 
Bob Bobserson
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Engineered soil seems like it would be necessary for really difficult soils....but I don't know if all would need that. Like here in California, outside of my house is a 15 foot tall unsupported cut out of a hill (we live on a mountain, so houses going all the way up). Even unprotected this ground isn't going anywhere (and that is in an earthquake prone area even).

It sounds like the Irish were trying to solve the moisture issue just through aggressive drying and heating inside of the living space in an effort to make it more comfortable....but unless the moisture is kept far away from the walls (from the outside), structural stability is constantly shifting....and a bad rain would turn it to mush (which is why they had the cave ins I bet).

Now aday I think a full water management design could solve a lot of those problems (drains, landscaping, waterproof linings covering a larger area). Even the moisture inside of the living space wouldn't be enhanced by additional moisture from the walls (which seems to be the case with a lot of underground structures).
 
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Have you read mike oehler's 50 dollar and up underground house book? I think you would dig it (haha unintentional awesome pun!) because he does a good job of addressing the sort of questions your asking. Also he totally presents a wide range of options from super small minimal dugouts to much more elaborate, multiroom homes. I don't have any practical experience with this but it just strikes me that you would really enjoy mr. oehler's take. There's the wofati stuff on here you can look at as well.
 
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There is another issue that has not been covered.
If it was a truely great concept, it would be in operation today.
I have read the diaries of travellers and early settlers in the uSA, I have read many books on alternative building and dug outs dont rank highly.
I am not trying to 'dampen '' your thoughts, but be realistic, there have been good suggestions, worth considering.
I can say digging such a hole in itself is hardwork, so why not use any improvements and experiance mentioned.
 
Bob Bobserson
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John C Daley wrote: If it was a truely great concept, it would be in operation today.



I'm sure people could have said the same about earthship design a little while ago when it was first proposed as well...

What we do today isn't perfect, there is still room for rethinking and revisiting older techniques (under a modern lens).

The problem with earlier settlers accounts of dugout style houses is they didn't have the materials to really handle moisture. Pond liners weren't a thing back then...so they were left with wet soil during rain and just doing the best they could.

But these types of earth structures are some of the earliest buildings mankind used for thousands of years (and they are found across every continent). Only today we have the easy access to materials like a pond liner that can make waterproofing the entire area a breeze (the same with modern digging technology to make the task of digging the hole a job for a single person in a day or two).

It is still dependent on the soil you have to work with.....but the big question just comes down to if you can manage the moisture well enough around the area and protect it all with something like a pond liner. I can't think of a reason why that shouldn't be possible? And, actually, thinking about it ...it seems downright easy.

 
Travis Johnson
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Ivory Oasis wrote:It is still dependent on the soil you have to work with.....but the big question just comes down to if you can manage the moisture well enough around the area and protect it all with something like a pond liner. I can't think of a reason why that shouldn't be possible? And, actually, thinking about it ...it seems downright easy.



I think it is possible, but I do not think it is easy, in fact I think it is quite the opposite; rather difficult. I am not trying to be a naysayer on this, but I think hydraulic pressure of water in soils is a difficult thing to contend with. It is not very often in nature a person sees water running uphill, but that is exactly what a person is contending with here.

In a conventional home, it is bad enough, and I think the insurance companies could provide plenty of statistics on how much water damage is caused to finished basements overall on a yearly basis. However they are only a few feet deep. An entirely dug out house is deeper and subjected to a lot more hydraulic forces. Pond liners by design help to keep water INSIDE a pond, and use the weight of the water to aid in that. In the case of a dugout house, they would be used in trying to keep OUT water, and fighting against the pressure of that water; two different roles.

Then there is the soil itself. Again, in a conventional home, the loads are so light and predictable that it is barely a problem to consider; almost any soil can be built upon. That is not the case with a dug out house. Clay, which is hard as a rock in drought, becomes slumping slime when it is wet. And even the gravely loam that I have here, while well draining, is also highly erodible.

I even have a house with a dug out basement, lined with field stone and it has some benefits even with a conventional home above it: it stays really warm in the winter. But as well draind as it is, during the spring its ability to drain water is superceded by the amount of rain and snowmelt and so it floods. In the basement of an old house...irritating, but with a dug out house it becomes debilitating at best, and dangerous at worse. Now add in 5, 10, 25 and even 100 year floods, and a person with a dug out home would have to plan for a system of drainage thatis not only adequate, but about 500% more adequate.

Then there is overall safety. Poisinois gasses tend to sink, so it is possible that just an idling car could send exhaust down into a dug out home that cannot be vented killing the occupants. Or the lack of draft on a stove on a cold, foggy morning sends the smoke into the house where it cannot escape.

I am trying to think of one example where underground living was a positive experience and cannot think of one. Prairie houses of sod. Irish during the potatoe famine. World War I trenches. World War Two bunkers. Even the most remote, poorest parts of the world live above ground. To this end Paul Wheaton and his WOFATI is an above ground structure COVERED in soil, and Mike of the $50 Underground House has admitted his house was more bermed up, then dug out.
 
Bob Bobserson
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Travis Johnson wrote:I even have a house with a dug out basement, lined with field stone and it has some benefits even with a conventional home above it: it stays really warm in the winter. But as well draind as it is, during the spring its ability to drain water is superceded by the amount of rain and snowmelt and so it floods.



I'm curious how are you handling the drainage around the property before it comes near the house and the strategy to keep it from the basement?

Knowing where things went wrong could help to design to fix those problems.

My theory is a very generous water barrier + deep drainage around the perimeter should keep water from getting into the ground near the structure (so no soil to soil moisture transferring, and no top down moisture coming....and the capillary action of soil isn't enough to force itself up feet worth of space). And condensation issues would just make it uncomfortable (though, unlike other underground houses, since there is no moisture in the surrounding soil....it shouldn't have unusual humidity with proper air flow).

The problem is, like you point out, most of the examples are of dugout structures aren't solving for the water problem....so of course they are having water issues (even into catastrophic cave ins as the soil is destabilized with too heavy of rains).

I'd love to find some examples of the approach to trying to manage the water in the soil all around the area (instead of just at the house point).
 
Travis Johnson
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Ivory Oasis wrote:I'm curious how are you handling the drainage around the property before it comes near the house and the strategy to keep it from the basement?



Well...not very well.

In this case, I live on a big hill, and the house itself is situated so that on all four sides, water drains away from the foundation. And on one end there is enough slope, and a pipe to drain away what accumulates for water away. That is about it. As I said, 99% of the time it is fine as far as being a dry basement, but during the spring when rain is hapening, and snow is melting, there is enough hydraulic pressure to force the water inside the basement through the fieldstone lined walls...exactly what a dugout house would have for a problem.

Now me, what do I care, I live above the basement in a house and just use the basement for limited storage? What is down there I care little about, but that is NOT the case with living down there. If its wet, I do not go down there!

To live down there, sure...like someone in a dugout house thay could backfill with rubble, use pond liner, and use 8 inch drainage tile so in a 25 year flood an enormous volume of water would be trapped and then flow away to daylight...but what is the cost of all that? Possible? YES! At a cost that is comparable to a WOFATI that is built on top of the ground and then covered with earth so that it is sheltered and given mass? Comparable at best, and most likely more expensive.

It is a pretty simple concept. Dig a big hole and when it is dry out it will be dry. And when it is wet out it will fill with water. Now we can change that easily enough by doing this, that, and the other thing, but then it all adds into cost, which being inexpensive housing was the SOLE purpose for doing it in the first place. Take that away, and it is no longer worth doing. Add in safety and comfort factors and it REALLY is not worth doing. So then it begs the question; can we build above ground using cheap methods, and the answer is YES! Building a WOFATI or other ways often talked about on here is probably is cheaper, and a lot more Green in nature as well.


 
Bob Bobserson
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In this case, I live on a big hill, and the house itself is situated so that on all four sides, water drains away from the foundation. And on one end there is enough slope, and a pipe to drain away what accumulates for water away. That is about it.



It sounds like you are dealing with some surface water with the slope (depending on how sloped it is)....but nothing for ground water? No wonder it is filling up. The problem isn't hydraulic force (?? the pressure of water underground isn't really much....cracking from water comes during frosts, that type of force does get substantial), it is just normal water moving to areas of lower pressure (and a big open void next to it is a pretty good candidate as it leaches through the ground).


To live down there, sure...like someone in a dugout house thay could backfill with rubble, use pond liner, and use 8 inch drainage tile so in a 25 year flood an enormous volume of water would be trapped and then flow away to daylight...but what is the cost of all that? Possible? YES! At a cost that is comparable to a WOFATI that is built on top of the ground and then covered with earth so that it is sheltered and given mass? Comparable at best, and most likely more expensive.



Not if you design to manage the water BEFORE it reaches the boundary of the foundation. The design I propose is managing the water far away from the building.....not only in the slope , but ALSO keeping water from penetrating deeper into the ground near the house (using a pond liner extending far around the area)...AND underground water drainage for any water coming in laterally before it enters the area....

If you don't stop water from all the ways it can get into the house, then of course you will have water issues. It isn't about doing "some water management", it is about doing a complete system of water management to keep the ground dry.

It is a pretty simple concept. Dig a big hole and when it is dry out it will be dry. And when it is wet out it will fill with water. Now we can change that easily enough by doing this, that, and the other thing, but then it all adds into cost, which being inexpensive housing was the SOLE purpose for doing it in the first place. Take that away, and it is no longer worth doing. Add in safety and comfort factors and it REALLY is not worth doing. So then it begs the question; can we build above ground using cheap methods, and the answer is YES! Building a WOFATI or other ways often talked about on here is probably is cheaper, and a lot more Green in nature as well.



The cost of what I'm talking about should be far less than something like a wofati (or any traditional house). You essentially just need digging equipment, crushed rock, and a pond liner....

Wofati are just buried log cabins. I'm not really a fan of their design. They don't seem to be dealing with the underground moisture issue to a far enough extent to avoid the high humidity and moist soil (which will eat away at their wood and make pests a problem).

Wofati are also pretty expensive since they use a TOOONNN of wood. Unless you live in a forest and are logging it all yourself (still expensive in terms of labor and equipment).

 
Travis Johnson
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I have a different opinion on the matter, but say so in utter respect.

A lot of that might be based on my area, which is owning two houses here in Maine, and one in New Hampshire. Of those three, one had a slab-on-grade foundation, while the other in Maine has a fieldstone foundation, while the one in New Hampshire has a basement of concrete. I have water issues with the two houses that have basements, both of which flood in the spring of the year.

My dislike of the concept of a dug-out house is more based upon experience than theory. That being; while in thoery water moves with gravity, that has not been my experience. For instance, everything in the world says a person siding a conventional house should think like rain, and protect the structure going from top down, but few people building a conventional house consider wind-driven rain being driven UP into crevices that were never provided protection for. In the earthmoving world, I have seen numerous water barrier protection systems fail, and many designed by engineers. This is not in disrespect to their profession, but rather because of my astonishment of the powerful hydraulic forces in action that exists in nature. In fact it is the main reason I support Permiculture overall, it works WITH nature instead of against. To me, digging a big hole and then trying to keep the water out is silly in terms of a dwelling where life and property is at risk. A cheap livestock barn? Sure, in fact in my farming classes I do a scale model of engineered soil and a dug out/WOFATI!!

In terms of both good and bad, I have been digging away and hit springs with my excavator and filled a pond wonderfully, and yet others times flooded out the foundation of a new dwelling. Equally I have been told by soil engineers that "bedrock was at least fifteen feet deep", and my bulldozer chattered over the ledge with its 3 inch grousers. I have dug to the depth of my boom and been in nothing but gravel, and in the length of fifty feet been scraping berock on top of the ground. The point is, the older I get, and the more earth I remove, the more I realize just what a crap-shoot it is when you start to dig; a person never knows what they are going to hit.

But life is about risk, so living in a hole is a way to survive, but I love the concept of a WOFATI because it is more about covering then it is about digging down.

I live in the most forested state in the nation so I have plenty of forest resources, but I like the fact that WOFATI's have plenty of options. I would probably use steel roofing with framing to get me a workable WOFATI using less forest products. I would do that because I have sawmills and can use them to my advantage, but for those trying to build and ultra cheap, ultra green WOFATI...I fully understand what they are trying to do. Again, I have a mine and quarry, so another possibility I have, is to build a form and pour concrete to hold the weight of the WOFATI roof. Again, not for everyone, but the point is, USE WHAT YOU GOT, and it is a design that is very adaptable.
 
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A friend and neighbor who just passed away last year, lived in his pit house for 30+ years, in high desert Arizona. Biggest issues were bugs, (things like kissing bugs and centipedes) moisture (when we get some) and the roving bands of cows. He would wake up in a sweat whenever the cows got on top of his roof. Local inspectors have never found his home as it is hidden on the backside of a communal property so he never had building code issues.

He loved his home, it was a comfortable one man home for 30 years and if cancer had not taken him he would be there still.
 
Bob Bobserson
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He loved his home, it was a comfortable one man home for 30 years and if cancer had not taken him he would be there still.



Yea, pit houses and other types of these houses have been used for soooo long. If we could solve the moisture / stability issue (pond liner + proper drainage to keep water away)....these would be such cheap alternatives to some of the more labor intensive types of natural houses.
 
Daniel Richardson
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Bob, are you going to give this idea a go? I kinda want to see it!  I saw a guy use a pond liner for a roof in Grand Designs S14E06 on Netflix, though it wasn't a pit house.

I couldn't think of any good way to solve the insulation problem without the foam board.  You can see effects of moisture without insulation in S13E04.

I do think that you might be able to get by with less if you used a ditch witch or a small bucket on an excavator to dig a deep trench around the room, dropped a sheet of 2" foam board in vertically, and back filled the outside with gravel.  If you had a heat source, the soil between the insulation and the room might eventually stabilize above the dew point.
 
Bob Bobserson
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Bob, are you going to give this idea a go? I kinda want to see it!



Not for a bit, just thinking out loud at this point. Researching what others have done and where the pitfalls are.

I do think that you might be able to get by with less if you used a ditch witch or a small bucket on an excavator to dig a deep trench around the room, dropped a sheet of 2" foam board in vertically, and back filled the outside with gravel.



Yea, I was thinking along those lines. It isn't complete insulation (since there is still contact from under, but no real way to deal with that without digging out the walls....which turns the entire thing into an entirely different type of structure)....but hopefully enough to create a temperature grade to keep it comfortable inside? Dry earth does have some insulation properties (wet is horrible, but ideally the area around the structure should dry out).

Here is the current version of the idea.... terracing the walls means they can be supported by basic loose stone retaining walls (each one being 3 feet high, creating a natural seat / shelf surrounding the rooms (which can be turned into cabinets or closets, or just shelfing / seating)). And then a higher terrace that would give the entire room storage.



Roof wise "could" be done as vaulted....but this version is just super simple (the type used for quick bunkers). And shifts the load back a bit away from the opening. You would still get the sloped roof though, since the liner is placed on top of packed earth.



I saw a guy use a pond liner for a roof in Grand Designs S14E06 on Netflix, though it wasn't a pit house.



Thanks for the tip on the show! I was just checking it out and it looks like a great show.
 
Daniel Richardson
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Great sketch! I just remembered a website that I read 20 years ago that might help you...it's still up!  It has a copy of Nuclear War Survival Skills by Cresson H. Kearny.  It's a really good read with loads of practical information.

OISM.ORG





If I were you, I'd leave room to dress up the terraces from the inside after you backfill and let it dry some.
 
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I've thought about building a hobbit hole like this. All the hobbit holes I've seen online are basically just buried structures, sometimes not even that buried. In the book they are described as long underground halls, wrapped around a hill, with rooms on both sides. For the roof I wasn't even going to use a pond liner, just beams, crossbeams on top of those and sod on top of that. Should be waterproof if done tightly, and the smoke from the open hearth I'd heat and cook with should preserve the wood and keep it from rotting.

The main hall I was going to have level with the slope of the hill, the uphill side rooms a little more underground and the downhill side rooms poking out of the ground just enough to have windows at the top. Of course the uphill rooms would have to have steel beams or something to keep them from rotting and collapsing, and the downhill ones would need vertical corner posts since they're partially above ground. Also steel drainage pipes so the roof didn't leak where it interrupted the slope of the hill.

Since a hobbit hole isn't supposed to be nasty or dirty or wet, I was gonna cob the walls and paint over them with lime for waterproofing and that nice whitewashed look. Also a red brick and cement floor, nice rugs, LED candles and other niceties. I'm sure a simplified version without the side rooms and with dirt floors and walls would work, I just wouldn't want to live in it.
 
Bob Bobserson
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For the roof I wasn't even going to use a pond liner, just beams, crossbeams on top of those and sod on top of that. Should be waterproof if done tightly, and the smoke from the open hearth I'd heat and cook with should preserve the wood and keep it from rotting.



I don't think that will be waterproof....and the wood, in contact with damp soil, will DEFINITELY rot. Trying to smoke it won't save the house from slowly deteriorating. Sod houses (or turf houses) usually have extremely thick walls and constantly need to battle with moisture.

And if you aren't waterproofing the surrounding soil, you are going to deal with water coming in through the walls (or even flooding). This will lead to erosion issues, insect problems, moisture / mold, frost heave....and poor insulation (damp soil is the worse).

Basically, the entire idea of the above is to try and tackle the common problems with dugout houses. To stabilize the conditions in the soil so you can stabilize the conditions inside for a livable space.

The main hall I was going to have level with the slope of the hill, the uphill side rooms a little more underground and the downhill side rooms poking out of the ground just enough to have windows at the top. Of course the uphill rooms would have to have steel beams or something to keep them from rotting and collapsing, and the downhill ones would need vertical corner posts since they're partially above ground. Also steel drainage pipes so the roof didn't leak where it interrupted the slope of the hill.



A larger structure in the hill would require excavation of essentially the top of the hill. And then you would need to rebuild it burying the rooms. But if also need to be careful the surrounding soil can support the roof (and the weight of all the soil you pile on top to rebuild the hill). So for that you need built walls....or, as I theorize, terraced retaining walls to increase the weight load / stability of the walls.

Since a hobbit hole isn't supposed to be nasty or dirty or wet, I was gonna cob the walls and paint over them with lime for waterproofing and that nice whitewashed look.



Well....cob needs to breath. That is why it doesn't work so well up against soil (ESPECIALLY damp soil, which will all absorb into the cob walls and be miserable). Lime won't waterproof anything either....you need to deal with the moisture in the soil or it will just seep into the house.

Don't look at hobbit houses for inspiration. That is fantasy from a fantasy writer. Look instead at traditional underground or earth bermed houses. These were the first kinds of houses and used for thousands of years by native people around the world. From the turf houses to the pit houses to all sorts of dug out shelters....right up to modern bunker design. There are a lot of designs that use the earth as part of the building, instead of just an obstacle the structure is fighting with (which conventional underground homes do now).
 
L. Tims
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Well the open hearth smoke preserving the roof wood thing I saw on a documentary, some native group did it in their underground houses and it apparently worked. Maybe they turned the roof logs occasionally so the same spot wasn't touching the dirt all the time and got a chance to absorb some smoke? You're probably right about water coming in through the walls and cob not helping though. Maybe concrete those too? Then I've pretty much built a bunker I suppose. IDK, I'm not dead set on a hobbit hole or anything. Just something I might try, secure in a more realistic house.
 
Bob Bobserson
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Welp, continuing on this idea....I started to play around with some actual designs.

I figured a 3 foot rise to a 2 foot back on the terraces should be enough for the retaining walls (even though they are just extra insurance, since there won't be moisture in the ground around the structure). That means the terraces themselves eat up 6 foot along the walls on each side....which made hallways far too large to make sense. So for hallways I would instead do steeper terraces with additional pole supports? Also making them longer than normal to avoid those sharp curves and leaving enough earth for the walls.

3 foot also happens to be the right height for kitchen (and other) countertops in a house....which means you could finish them with tabletops.

For work desks or bed (which are a little lower), cutting into the terraces a little made sense. Losing a little height I doubt would destabilize everything on the last terrace (and actually, for the bed, it is extended out to sleep on) 

Also, when I was considering it, doing sharp angles in the house wouldn't leave enough earth for structural support for the roof. This meant they needed more forgiving curves.

Here is the general idea....



And this gives a better view of what is happening with the walls.



And here is a view that gives a better idea of the living area. Seems spacious enough for a decent place.

 
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