New Mexico Dirtbags

Earthbags 


These pages are just a brief
introduction to earthbag construction. If you're new to it, we offer an overlook to the fundamentals. There are plenty of books & websites out there that go deeper into the subject than we do. The best way to learn, though - as with so many other things in life - is by doing. Getting your hands dirty, so to speak.

Start with the basics. Take some clay-rich dirt in your hand. Moisten it, squeeze it, roll it into a snake. Now add a little sand, squish it into a form, lay it in the sun & let it bake for a few days. It gets hard. Congratulations... you've just made adobe.

If you put this wet clay/sand mix in a sandbag & stack the bags, pound them flat, smoosh them around to your liking (straight lines, curves, rounded corners, whatever) and let them dry, then you have earthbags - modular building blocks, adobe bricks in a bag.

Alternatively, filling your bags with dry scoria (lava rock) avoids the need for mixing soils or adding water. The voids in the scoria provide significant insulation (R-value), the bags are lighter in weight (easier to work with), you can buy them from us pre-filled if you choose, and you can build year-round (unlike earthbags, which require warm daytime temperatures for the mud to cure).

With the right fill & a little finesse, earthbags are stronger & more stable than concrete blocks. They're low-cost, low-tech, have a relatively low carbon footprint, they're fireproof, and - depending on your fill material - are free of the chemicals & outgassing that are increasingly common with many modern building materials. 

History:

The idea of using dirtbags/earthbags isn't new; think of the sandbag trenches &WWI sentry fortifications from World War I. There are suggestions that they were used as far back as the Revolutionary War. The Industrial Revolution allowed mass production of textiles; before that, baskets filled with dirt & rocks (the predecessors to gabions) were used for fortifications as far back as Mesopotamian times.

But the application of bags with a wet fill (mud) that'll set up, as an alternative building material, is fairly new. It dates back to around the 1960s and can be largely credited to two individuals.

One was Edward Dicker, who patented the "Stack-Sack" process in the 1960s (burlap sacks filled with a dry mix of sand, cement, and gravel; soaked in water & then stacked, with rebar driven through every couple of feet to anchor them).

Further refining the concept was Iranian architect Nader Khalili, humanitarian and founder of the Cal-Earth Institute, who recognized that people left homeless in war zones and disaster areas around the world often have (if little else!) abundant access to three things; sandbags, barbed wire, and dirt.

Earthbags are ideal for bordering sinuous walkways, garden beds, terracing, erosion control, building arches, serving as foundations or stem walls for cob or straw-bale constructions, or more ambitious projects. Once they're fully cured & well plastered, no one would know that they're not adobe (or something more conventional).


Advantages:

  • Aesthetic - easily covered with plaster or stucco
  • Versatile, graceful, and easy to work with
  • Fireproof
  • Non-toxic - no fumes or allergens
  • Low-tech, requiring a minimum of tools or experience
  • 12" thick walls provide superb insulation
  • Stable; superior earthquake, tornado and hurricane resistance
  • Tamped dimensions of standard 14"x26" bags at a manageable 30 lbs each = approx. 12" wide by 12" long by 3" high. If you choose, you can pack up to double the amount of fill in the same size bag to achieve a 60 lb. bag with tamped measurements of about 18" x 12" x 4". (Bigger bags mean fewer bags, but they're much harder to manage.)

Making your own:


With the basic materials (bags, dirt, barbed wire to lock rows of bags together, and a tamper), anyone can design and build with earthbags. If your dirt doesn't have sufficient clay, you can add it, or stabiize it with lime or cement.

You don't even need to buy bags. Sure, we're happy to sell them to you. But some people have had success using alternatives like thrift-store pillowcases, sheets sewn together, etc. The point is to have a container or wrap that will hold & confine the wet fill, and that will survive the tamping without splitting a seam. Once the contents of the bag have cured & and your construction is plastered, it doesn't matter at all (structurally speaking) what the bag was made of.

If you're new to this, you'll find information, links, and resources on these pages & elsewhere to help you get started.


Empty bags
(
click HERE to see prices):

Standard polypropylene bags are14"x26" (approx. 36 cm x 66 cm) and can hold up to about 50 lbs. of fill. These are medium-weight (10x10 weave, 850 denier, superior to the cheap bags sold online), have tie strings, and are UV treated to provide about 6 months of protection.

Large polypropylene bags are the same as the above, but measure 18"x30" and can hold between 75 and 100 lbs. of fill. These can be difficult to manage when using for building.

Natural burlap bags (new, additive-free, 9 oz. weave, 14"x26") are a bit expensive for construction but are excellent for gardening and matanzas. We occasionally carry larger untreated burlap bags (18"x30" and 23"x40") which, among other things, are just the thing for sack races.

Treated burlap bags (dipped in a copper solution to help prevent rot, mildew & to deter critters) run about 12"W x 14"L and are $2.00 each. These meet US military specs CID A-A-52141 and are made in the US. Good for erosion control and that underground bunker that you've been thinking about.

Specialty bags
include:
 
  • Heavy-duty polypropylene bags (14.5"x26", rated for 4 years). More expensive than standard ones, they're tarp-weight and will pretty much withstand anything that nature & the elements can throw at them. Available in any quantity, they're best suited for long-term deployment for flood or erosion control.

  • Polypropylene tubular bags (otherwise known as Superadobe) come on rolls in several widths & lengths. We can get these in a variety of widths & lengths. These are special-order and require advance payment, but come with free shipping.

  • Monofilament bags (assorted sizes) are typically used for filtration, storm water control and ballast. They last for years and can be emptied & refilled multiple times. Nice to have behind your back seat if you get stuck in mud or in snow.

Tools:  

We provide 4-point barbed wire in rolls or by the foot. This is used between the courses of bags to lock them together. We also provide tampers, bag fillers, sifters, zip ties, trowels - pretty much anything you need. See our store here

If you live out in the boonies & want us to find you something to add to your order (whether it's a mantle for your Aladdin lamp or chocolate espresso beans from Trader Joes), we'd be happy to look around & give you a quote.


Plastering:


After building, you'll need to cover your structure. Popular materials include lime, cob, adobe mud, papercrete, stucco, and earthen plasters. Typically, you'll want to add one or more rough basecoats, and then a finish coat that will add color, texture, durability, and weatherproofing. Check out our plastering/rendering pages (in progress!).
 



* New Mexico residents, please add NM gross receipts tax of 7.5% to all orders.
All sales are final. Defective merchandise will be cheerfully replaced at our discretion.

505.750.3478 (DIRT)
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USDA's NRCS
Web Soil Survey
mapping engine

to see
what kind of soil
is on your land!
 


Soil type testing guidelines HERE




Why not to use
concrete (cinder) blocks




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