Building with earthbags is essentially building with adobe bricks without going through the lengthy process of making them. You take polypropylene sandbags, fill them with a moist mix of sand and clay, tamp them down hard and connect the layers with 4 point barbed wire. Then, you cover them over with an earthen plaster.

In reality, I didn't use polypropylene bags. Some Brasilians started a type of construction they call hyperadobe which uses mesh bags, or continuous tubing, made from the same material as the onion or potato bags in the grocery store. They don't require barbed wire, though otherwise the process is just about the same.

As I talk about in the blog posts, my design has been guided by simplicity and efficiency. More than anything, what's been most important to me is to live in a house that I myself, with no building experience whatsoever, can design, build and maintain. A natural extension of that has been the desire to live in a peaceful space. For me that means a home that's in tune with nature, thus limiting the use of imported materials for construction, in addition to those that will be needed later on, such as for heating. Please enjoy reading, ask me any questions, get inspired, and come help and learn!

Monday, February 21, 2011

The Inner Design

Simplicity and long-term efficiency have been the driving forces behind my design from the beginning. Straw bales originally appealed to me because of their high insulative value. After reading my 30th book or so, their building complications--mainly the need to compress them via the roof or straps before you plaster, in addition to keeping them totally dry until that happens--began to outweigh their apparent efficiency. At about the same time I started to understand thermal value vs. insulative value and the benefits of New Mexico's unique climate. Despite the fact that winter temperatures can get to -30 Fahrenheit, Taos enjoys 300 sunny days a year. While insulative value (r-value) will prevent outdoor temperatures from getting into a home and vice-versa, thermal value (u-value) allows a material to store and release heat over a long period of time. Dirt has a high u-value. The exterior and interior walls, in addition to the floor, will all be made from earth and thus have the ability to soak in the sun's energy and release it during cold nights and on cloudy days. This, coupled with the house's passive solar design--short width, long length, windows primarily facing south--will allow me to use the sun as my primary heating source year-round.


Back-up heating will of course be necessary. Originally I was planning on using a woodstove. However, once I discovered that I can build my own--check out the Rocket Stove book--I decided to do that instead. A significant plus in the Rocket Stove design is that you can funnel the flue through cob benches that will be my living room couches and guest bed. What is cob? It's a clay and straw mix out of which I will be creating built-in furniture and interior walls. The heated cob benches not only make a toasty place to hang out, but they will store the heat and release it back into the room long after the fire has died down. I will definitely have one in the kitchen/living room and possibly a second to heat my bed. I will also use the stove to cook in the winter. In the future I'm planning on adding an outdoor summer kitchen with a propane stove. Meanwhile, I will build in a propane connection to the indoor kitchen in case I want to add a propane stove in there as well.


Water will be from rainwater catchment from my metal (or ferrocement?) roof. I will build four 800 gallon above-ground ferrocement Thai jars--check out Art Ludwig's Water Storage book--and use a solar powered pump to push the water into a pressure tank which will supply the house with pressurized water to the tap via 1/2" PEX (a type of HDPE) tubing. The same pump will supply a 20-30 gallon water heater that will be connected to an outdoor solar water heater via thermosyphon. New Mexico has a pretty low precipitation rate. On the plus side, however, there is precipitation all year long so storage capacity does not have to account for long drought periods--at least not typically. My water consumption will have to be quite frugal. Not having a washing machine or water-consuming toilet will help significantly.

The toilet will be a simple composting toilet. You can spend a couple thousand dollars or more on a commercially produced composting toilet. But I'm going for simplicity. While you can make your own composting toilet, it would have to be outside and I want an inside toilet. Joseph Jenkin's awesome Humanure Handbook tells you how to build your own sawdust toilet and compost your own poop. Simple and efficient, it gives you back rich compost for your plants, trees or veggies, depending on your level of comfort.

All waste water will be directed out as greywater via 1" PEX tubing. It will go straight to trees or plants so that my sink and bathwater will not go to waste. It has been useful to read about permaculture design so that I have an idea of where I want to go with the landscape and plants' different water needs and ph tolerances. Greywater tends to be alkaline, rainwater tends to be acidic. Though I'm not sure, I'm guessing that my greywater will be pretty neutral since I'm starting with acidic rainwater whereas city water has a higher ph. Additionally, you can use greywater friendly soaps to keep the ph down and to add in things that will make plants happy. I'll probably start making my own cleaning products and soaps according to the garden needs.

Electricity will most likely eventually be added in via solar panels. For now, I'm just including service tubes in the design to push the cables through later if I choose to.

The house itself is more or less 16' by 38' interior. I will hire a backhoe to dig out the shape two feet wider than the finished interior area, three feet deep into the ground. The walls are 15" thick except I decided to do 19" thick walls on the south side because there are a lot of windows and doors for the passive solar and I did not want to compromise the structural integrity. Buttressing will also be incorporated on the interior around the two doorways. On the north side it will continue up to ceiling height, whereas on the south it will go up to grade level. Its purpose is to make me feel better about the pressure that the surrounding earth will exert on the structure. Stairs will be built in later with cob for the two foot drop from the door to the floor.

On the outside, around the bags, from three feet down up to ground level, will be 9" pumice for a capillary break from the surrounding earth and insulation. The bottom course of bags will also be pumice--capillary break. Above that there will be 6-8mm black plastic tucked under the first course of raw earth bags that will continue up between the bags and the pumice, then get tucked underneath the first grade-level bag. Tucked in at the same level will be soaker hose which is used as a weep screed--a simple capillary break down to which I will plaster. Luckily New Mexico is dry. Otherwise, there would be all sorts of other things I would do--which it might turn out I need to do anyways--like not plastering down to grade level. But since there is that 9" of pumice between me and that dry ground, I'm not worried about moisture migration. It will rain and it will snow. But except in the case of a flash flood, the earth bags and the breathable earthen plaster should dry out without a problem.

The windows and doors are approximate as I am hoping to find free or cheap fixtures and thus have to be a little flexible. The south door onto a future flagstone patio will be a 5' width sliding glass door. Both the doors and windows will begin after one course (6") of bags above grade level. I have had to juggle some height limitations due to the roof height which as of now will be ten feet in the center and seven or six feet on the ends. That, of course, translates to eight feet above the ground in the center and since two courses of bags have to go on top of the lintel--which in the case of the large patio door will be ten or so inches thick--I can't really get away with a door more than 6.5' high and windows 5' going down toward 4' as the roof slopes.


As far as the roof is concerned, it's still up in the air. I have been planning on doing 8" vigas spaced on 30" centers, insulated with 8" of pumice and topped with a metal roof--somewhat reluctantly after I got attached to the unrealistic idea of an earthen roof. But now, I have opened my mind to a ferrocement roof which seems like it could be the best solution. There are also a lot of other options for roof insulation, from rice hulls, to fiberglass batting to blown cellulose. It would be neat to find a non-recyclable waste product like Styrofoam peanuts and insulate with that. Regardless, the roof will come together soon. Honestly, ferrocement didn't occur to me until today. While it seems like the obvious choice, I'm going to geek out on it for a little while to see if it actually is better than a metal roof. If it turns out that it's a no-go, I have metal roof plans that will work out.

Think I'm crazy? You'll have to come out to New Mexico to find out for yourself. Don't worry, there's plenty of work for everyone.


  1. Wow, looks like you have been putting a lot of thought into the house. I like the idea of rainwater catchment. If you use a ferrocement roof, the water will most likely be alkaline. Desert soil tends to be alkaline as well. Organic soil amendments work pretty well to lower ph, they also increase arability, water holding capacity and soil fertility. You may want to get some trees planted asap. The sooner they are in, the sooner they can provide you with some wind protection and shade.

    Are you just using scoria in the foundation, or are you going to build the entire house with it? Unfortunately I have a healthy layer of sandstone where I want to build. There is not a lot of earth available close by to use for bag fill. I will have to have some scoria hauled in or pick it up in my truck. I think I will save as much topsoil as possible for some raised beds.

    What elevation are you at? I am at about 6000 ft. I suspect our climates are pretty similar. Your vegetation is a bit different, I have
    large juniper and bunch grass around me.

    How much do you have figured money wise to build your house? Owen Geiger thinks they can be built for 10 dollars a foot. With the cost of fuel driving up other costs, I am not so sure.
    I have been looking at Owen's Enviro Dome. It looks good, but I may go with something with a bit more conventional roof. The shed style you have looks promising.

  2. Was just using scoria on the foundation, but may not use it at all.

    I'm just under 8000 ft. Couldn't really say money wise, only guesses. I can tell you in a few months :-)

  3. Hey Alyssa! It's Miwa here, from the Vipassana course. Just started checking out your blog a bit and it is all making me smile. Meeting you made me smile and made me feel empowered that I CAN also do this! Also, it looks like you have been quite detailed in your descriptions here, which I much appreciate as it is nice to kind of compare notes and processes with someone. Well, it was so great meeting you and I really do hope our paths cross again. It's wonderful to meet another strong little woman (coming from another small woman) making her dreams come true :-) Keep at it! (and btw, my blog is http://sculptingearth.wordpress.com/)