How do you make an earthbag cellar double as a survival shelter?

The recent heat wave in my area got my family thinking again about making a root cellar. We need a cool place to be if the power goes out and it goes over 100 again! If we make a root cellar, we might as well make it be a survival shelter, right? I think it'd be grand to have the structure act as a cellar when we need it to, a cool place to sleep when we need it to, a shelter to stay in if an earthquake hits and breaks our home, even a shelter if there's nuclear bombs. One shelter for all disasters.

But, the temperature and humidity of a cellar is supposed to be 32-40, just above freezing, right? And a humidity in the 90%. That doesn't seem like something I'd want to live in for more than a day or two, let alone with my kids who'd be cold even in sleeping bags.

Is there a way to make the shelter flexible enough that we can heat it and lower the humidity if we need to sleep in it in winter because a disaster made our house unlivable??  

The temperature of a cellar will depend on local conditions, it's whatever the "ground temperature" is in your local.

While I know nothing about earthbag structures or a wofati, it seems to me that building a wofati would be the ideal structure for making a survival shelter/root cellar.

I wonder if anyone knows of a price comparison between building a wofati vs building an earthbag structure, especially on relatively flat land.

There is desired temperature for a root cellar, then there is the reality of what can be accomplished in a region. I think the most important thing for me, is that nothing would freeze in the winter. Here, that is easy, as ground frost depth is 6 inches here.

This site says that "The temperature for caves in Tennessee is an average of 58 degrees." That is year-round.

Hmmm. And that is for caves. Caves have multiple feet of earth insulation on them. Anything I would build would likely have 2 feet of earth or less on top of it. My memory of playing near the entrance inside a few caves tells me that the closer one is to the entrance the warmer it is. I think my cellar would be a bit warmer, being that it would not be that "deep" in the earth. I think I would need to build my pretend shelter by digging down, only having the roof at the surface, then lots of earth piled on top of it. I suspect this design would not be structurally sound with the earthbags. At least, not for the roof. I have not checked with an engineer.

Does anyone know what the passive temperature of the wofati is in Montana? Perhaps this information would give you a starting place toward what is possible in your region?

Anne Miller wrote:I wonder if anyone knows of a price comparison between building a wofati vs building an earthbag structure, especially on relatively flat land.

This would be *really* difficult. If you've got lots sandy/clay soil to fill the bags with, but no large trees you want to thin or are standing dead, earthbag may be a better choice.
If you're in a climate where humidity is really high, a wofati may have mold problems that earthbag may not.
There are just too many variables.

Even the concept of a "root cellar" changes depending on one's need. Keeping fresh veg like cabbages and carrots crisp for a long time requires a low temp, humid condition, so you'd do things to help this happen regardless of the soil temp by bringing in cold early morning air (we get coldest somewhere between 3 and 6 am normally.) If you're storing onions or squash, they like it warmer and dryer. If you just want to store canning jars to keep them cool and out of the light, dry and 50F is just fine and far better than sunny and 85F for preserves!

A root cellar is high on my wish list, but the more I read about them, the more I figured I needed a multi-chamber one with insulated doors and airflow which could be controlled in each. Some things shouldn't be stored together - apples will tend to ripen stuff faster that you might prefer ripened more slowly for example. This can actually help Michelle Reasor's desire to "combine" uses.  I've seen root cellars with different chambers, and the "entrance chamber" is the warmest one for things like canning jars, and that could be set up as a cool room for heat waves. The jars will tolerate a few weeks of warmth, so that area could be the survival shelter if a source of heat was included.

I'm sure I read that earthbag domes made with barbed wire between the rows of bags has been earthquake tested and survived well. However, I also recall that if used underground, they need cement mixed in for stability and unless you do double wall with insulation in between, they rely totally on thermal mass for their temperature moderation.

I haven't read of earthquake testing on the wofati system - anyone know of any? I do know that it relies on longer term thermal mass storage - heating up during the summer then that heat keeping it warm during the winter, based on work by John Hait (his book, "Passive annual heat storage : improving the design of earth shelters") Considering that the Japanese have been building earthquake resistant buildings for centuries, I have no doubts that a wofati could be built to survive a serious earthquake, if built with that in mind! Considering we've had 2 recent examples of "modern, concrete architecture" failing spectacularly, what you build in not nearly as important in my mind than how you build it!

In my ecosystem, I think my ideal would be to build a very strong storage out-building to be my survival shelter, rather than doubling up a root cellar for the purpose. I could kick out the stored stuff to under a tarp if I needed more space, but it would be designed to be cheap and easy to heat, as keeping people warm following a disaster is often critical, particularly if there are injuries. For heat wave survival, the ante-room for a cold-cellar makes sense. Sometimes a single building just won't do everything!

Anne Miller wrote:While I know nothing about earthbag structures or a wofati, it seems to me that building a wofati would be the ideal structure for making a survival shelter/root cellar.

I wonder if anyone knows of a price comparison between building a wofati vs building an earthbag structure, especially on relatively flat land.

Earthbag is supposed to be really cheap--just the cost of excavating and the sandbags, which are supposed to be cheap. People usually say something like $400 to build one. And, it seems a lot simpler than wofati. My husband and I aren't good at building stuff, and staking earthbags seems really simply. I don't like the idea of using so much plastic, though.

We're in the foothills outside Seattle. I tried finding out what our ground temperature is here, but all I get is people talking about how high the ground got in our heatwave. Maybe I'm not telling Google the right words?

I'm not sure if it's better to dig down deep into the earth, or to only dig down a little and cover with earth like a wofati. We get a lot of rain here, and the place we're thinking of building the cellar is on a hill and drier than other places....but it could still have water issues.

These people made an earthbag cellar up in Alaska, digging straight down into flat ground to make it. The water level was 10 feet down when they dug, and in the spring it rose to 3 feet. Their cellar flooded. They explain what happened at around 9 minutes into it. The cellar was only 1 year old when they filled it in!



I don't know if it would be better to just excavate down 3-4 feet, and then mound earth up. My husband wants to go down deep, but I'm afraid that would cause the walls to cave in.

I tried to get pictures of the area, but there's lots of salmon berries and ferns in the way. It's shaded under a bunch of trees and facing north.

Many old root cellars had two or even three rooms.  The outer room was for canned goods and airlock for keeping the inner rooms protected from the weather.

I have been reading about a young couple that built their earthbag root cellar under their deck.  This is a great concept since the roof was already built.

And I found lots of YouTubes about how to build one.

I would almost be tempted to build one if I didn't live among limestone boulders. I love seeing what other people are doing that I can't do.

I was chatting with my sister-in-law about root cellars, since she had one growing up at her dacha house in Russia. Her's was deep under ground (she thinks the ladder was at least 15 feet long, and when they brought food into the cellar, they'd have 3 people in action: one at the top handing food down and another in the middle of the ladder passing the food along to the last person down at the bottom). Her cellar was was made of wood, and it was always needing to be repaired. They didn't use it one year, and the next year it was too dangerous to use.

I watched the video you posted, Michelle, about the earthbag cellar gone wrong. Terrifying and depressing! I wonder if those issues be fixed by building into a hill, or would the shelter still need constant maintenance to resist crumbling?

Ape Cave is 4 hours away from Seattle. In the cave, "The temperature is a constant 42 degrees F." From here. 10 degrees above freezing is a temperature I could work with!

I watched the failed root cellar video. Bummer. I do think building it into a hill may work. Finding your high groundwater depth would be good.

I watched the video. I've done a bunch of reading about both earthbag buildings and root cellars, and I've got opinions as always!  

1. As Joylynn said, "Finding your high groundwater depth would be good." However, I'd find it and assume that 1) by disturbing the area, you risk water choosing the path of least resistance and finding your hole and 2) with weather weirding, we're going to get bigger extremes of wet and dry.

2. Everything I've read about earthbag building, says that the *only* safe earth bag shape is a perfect cylinder or dome. The one house I read about that tried to do oval, regretted it.  Maybe others have read about successfully using them as squares or rectangles, but particularly underground with really wet winters, it's like having an empty swimming pool and the force inwards is huge.

3. I've read a bit about some of Sepp Holzer's cold cellars and they're built into the side of a hill, he pays careful attention to the flow of water, and he runs a pipe from the bottom downslope out to clear air, so any water that does infiltrate, will drain away.

4. Many old-fashioned, underground "cold cellars" I've read about were under buildings - either the barn or the house. Thus they had a *really* good "hat" over them, and properly built house foundations stress the need for water to be directed away from the building on all sides. If the water table is as high as it is some winters on my property, I would still want to proceed with caution.  

5. Certainly there are many cold cellars that were built into sides of hills also, but in that case, most of them had some way of water that did infiltrate draining away. Nicole mentions considering that option. I'm wondering if up-slope of the area you're thinking about, do you feel you can encourage run-off above your proposed root cellar to flow away from your target area? A few logs strategically placed at an angle may be all it takes to redirect heavy rain.

So, having watched that video, if I was planning this, I'd look for a spot where I could control run-off, could add a lot of earth around the structure for insulation, and if I needed to go with earthbags to keep the price affordable, I'd build it round.  Being a pessimist and frequently being accused of  under engineering my projects, I'd build earthbag interior walls as abutments (although I'm not sure that's exactly the right word - the idea is to have a wall at 90 degrees to the exterior wall, but on the inside to support the outer wall).  These would have the advantage of giving different areas for different storage needs.

Well, well, look what I found...


From Alderleaf Wilderness College. What a cool name!

I researched root cellars a few years ago. Forgive my fuzzy memory, drainage went something like this. Dig a trench a foot below floor level. In this case, it would be on three sides. In the trench perhaps a foot below the level of your floor, surrounding the cellar, place perforated pipe drains, with pipes draining out to the ground level. If pouring a cement floor, do it now. Build your walls a couple of feet tall. In the trench, on top of the perforated pipe, have a layer of gravel, river rocks, or similar to the depth of about a foot above the drains. Tamp it down. Now you can fill the remainder of the trench with dirt, as the walls are being built, tamping as you go.

The trench with rocks at the bottom and dirt above would be located to the exterior of the below plastic[?] barrier which will be smooshed to the outside surface of the earthbags as the walls are built and the trench is filled. (The site does not explain this well.)


I really hope that makes sense to ya'll.

Joylynn, that makes total sense to me, and covers most of the exact points I made above. It's absolutely cute as a button, and the only thing I would add in our climate (Pacific Wet) is making sure there's a system of air-flow such as Sepp Holzer uses. My friend's reaction when this subject came up was that the food in many cold cellars in our climate go moldy. If I recall correctly, Sepp uses a pipe that's underground so the incoming air approaches the inside temperature before it gets inside and that it enters at the bottom and leaves at the top, so you get air circulation.

Cute as it is, it would be a *lot* of work. You'd probably need several work parties worth of friends and relatives! However, if you've got the strength, earthbag would be cost effective and as a building system, it is reasonably environmentally sound. Some people worry about the plastic, but this is buried plastic that won't get either solar degradation or movement which is what I think wears most plastic out. I would want to use the strands of barbed wire the books I read called for since I live in earthquake country. Also, unlike what the Alaska video shows, I would want to put a plaster finish on the inside. Without a plaster finish, the plastic will get damaged over time, and could contribute to early failure.

Judging by Joylynn's pictures, I would also make one larger than the Alderleaf College one appears to be. Particularly with the round shape, there may be "wasted space" as most shelves are straight and more expensive to get curved.

Good luck if anyone tries this - and please post pictures if you do.

Following earth bag construction for a bit. I favor this over any post and beam construction for its simplicity and sturdiness of the dome.
Also it will be faster to build, I think, depending on size and design. I plan to do a simple dome to use as cellar, shelter and off-grid getaway.
In my mind it's also an elegant solution that uses a basic, available material - earth. Add to that barb wire and synthetic bags along with some
wood, windows and what materials are needed for the interior. Many use cobb for the exterior and inside for floors and walls. Not too well
versed on that part. Have been scraping for details.

A suggestion is to try and find people within 100 miles of where you live that have Root Cellars and try to set up a visit to find out what the temperatures are like, how far down the building goes, the depth of the soil covering the building, etc.

Major things to worry about are flooding from the water level. IF the level is only a few feet down you might want to reconsider building - OR keep the depth of the hole shallow with lots of soil thrown around and on top of the building. Two other major problems are the weight loads of soil on top of a building and water seepage down through that soil. Engineer that roof to withstand earthquakes, tornadoes, and tons of soil. You DO NOT want that building/roof caving in on you if you're using it as a root cellar and shelter and/or intending to sleep/live there when TSHTF and everybody is going crazy outside.

ALSO, here is a good book on Root Cellars that I'm in the middle of reading.
ROOT CELLARING: Natural Cold Storage Of Fruits and Vegetables, by Mike and Nancy Bubel, Storey Publishing, 1991. I bought mine through Amazon. I do strongly recommend that you purchase this book and it has lots of answers for you. Like temperatures depend on how well the construction has been done, how good the air-flow/ventilation is inside the room, how your goods are stored in there, and how the entrance is set up (single door or double door). Your purchase will be money well spent. And there are other books listed there and INFO on the Internet for your benefit.

We had a cellar under our home when I was a kid. It was always cool, not cold, down there winter and summer. It had two small windows, and, of course, a thick flat (floor level) cellar door. I also have visited a log cabin locally that is a two story building with a pantry built under the stair steps plus a real Root Cellar dug down halfway and covered over with soil and it was much the same as our cellar but maybe just a bit more humid.

       Howdy Michelle and everyone else,


              This is a practical and excellent idea, combining root cellar and shelter for oh, what brouhaha may come and of course those things of a more serious nature. To that end, I would recommend the book, Nuclear War Survival Skills by Cresson H. Kearney. It is detailed in such a way that you find in books of yore. In addition, as far as root cellaring is concerned I have and would recommend Root Cellaring by Mike and Nancy Bubel.
             On another note, if memory serves, Nader Khalili was the originator if you will, of earth bag or super adobe etc. construction, which others have written about. This vernacular originates from arid areas and therefore, at least to my mind, would give one pause in understanding how it would translate to one's place. In your case, the foothills of Seattle. I'm of the opinion that PSP, post shore polyethylene, construction by Mike Oehler would be worth looking into. You can find some info about that here on Permies. Last, I like your tag line, "Just a mom, trying to do best by her kids." Good on you! and good luck on your project!


          Thomas

If your boulders are huge, could you build a structure between them, using them as end walls? You could use earthbags for the other walls. It seems that boulders would provide lot of thermal mass.
If they're not so big, could you build with them by mortaring them together?

i'll have to say "it depends". If I were to build a wofati where we live in the desert I would have to purchase the logs from a distant location that were grown in a much more distant location since the likelihood of finding locally grown trees that would provide suitable logs and in sufficient quantity and that needed to be cut down would be virtually nil.

Robert Yaklin wrote:i'll have to say "it depends". If I were to build a wofati where we live in the desert I would have to purchase the logs from a distant location that were grown in a much more distant location since the likelihood of finding locally grown trees that would provide suitable logs and in sufficient quantity and that needed to be cut down would be virtually nil.

Having an earthbag cellar would be more practical for you if that is the case. The more I learn about earthbags the more I like it.

And I can see how it would also make a great survival shelter.

There is a guy in Russia who has online training for biodome/earthbag structures.  I heard about him through Yuri who posts on permies.com occasionally.  Alosha, and his wife Zoya are really into natural architecture and his latest project is a super cool house combining all the best in biodynamic living.  He is actually doing a live training in Russia in September.  https://www.bioveda.co/

ventilation could make it warmer. Or a stove of some kind or another type of heat gatherer or producer. Even several people would warm it.

Considered his class last year before he sort of disappeared - don't know the story.
His course does seem pretty interesting but I don't anyone who took it. Does anyone?
I'd love to get into this if the current madness doesn't explode this year.

Now that's a job for a rocket mass heater!
They seem to be a natural together.