New Mexico Dirtbags / Techniques

Techniques...

Basic:

1.) Grab bag by neck with one hand & grab seam on bottom of bag with the other hand,
keeping bottom seam of bag parallel to ground.

2.) Invert bag, letting dirt run down towards tied-off neck. Shake bag, distributing dirt uniformally.

3.) Fold top of bag under & lay in place (butting this end up against the seam edge of previous bag).

4.) Give bag a good shaking to ensure even distribution of dirt (bag should be roughly rectangular).

5.) Continue laying bags, using tamper every 3-4 laid bags & checking your work with a level.

Part of what makes this fun is that this is an organic process. Shaking & sorting & patting
your dirtbags is something that comes easy. You'll quickly master an almost intuitive ability
to make corrections when irregularities pop up. Once it "feels" right, use your levels and then
start tamping (you'll find you can use your tamper to make corrections, too!).

Recommended
Tools:

Heavy gloves &
wire cutters
(for barbed wire)

Tamper
(essential!)

String level & twine

3 or 4 foot beam level

Torpedo level

2 - sturdy ladders & planking
(scaffolding for hoisting &
tamping bags as walls rise)

There is some controversy over whether or not the soil in your bags should be wetted before tamping. Moistened dirt generally
achieves a higher degree of compaction after tamping, and - when allowed to cure in hot weather - dries like brick. Additionally,
if your soil is clay-rich, pre-wetting will cause the clay will swell (expand). This could be a good thing.

The principle argument against wetting is that if your structure isn't quite vertical, or if you work too fast & get ahead of yourself,
or if the weather isn't quite hot enough (or is too humid in your part of the country)for a quick cure, your underlaying bags can
"ooze" (read: become distorted) from the weight above them.

Wetted bags are, perhaps, best achieved by mixing the soil with water in a wheelbarrow and then filling the bags. Messy, but this
gives you the best control over your mix. Two or three people can set up an assembly-line that's fast & efficient, and each person
  can trade off. This may be the best technique.

Since we provide pre-filled bags, we've experimented with a couple of different techniques to wet the dirt after it's bagged. (This
refers to the water-resistant polypropylene bags; burlap bags, obviously, are in a different category.)

One technique is opening the bag, adding a pre-determined amount of water, tying the bag closed, and then mushing it about (fun!)
till if feels suitably squishy.

Another technique (still in development!) is building what might, at first glance, look like a bed of nails - a piece of plywood, about
12" x 16" (the same size as our tamped bags), liberally embedded with nails. The board is placed on a horizontal bag on the ground,
nail points down, and the tamper is used to impale it. Since our pre-filled bags tamp down to a solid three inches, 16d nails (3 ½")
can pierce both sides of the bags in one fell swoop.

A good soaking with the garden hose, or placing the impaled bag in a tub of water, allows the dirt within to become uniformly
moistened, without compromising the bag's integrity. Exercising judgement as to 'how much water is the right amount' is crucial
here; overly-soggy bags won't tamp, they'll just splat & mush. Remember, this is an organic, tactile process (labor of love!).

The bottom line? For small structures (garden walls, raised garden beds, etc., we think it doesn't really matter. However, for larger
structures (most especially anything you can walk into, much less live in), we believe that safety & structural integrity are better served
by using wetted dirt & allowing it to cure or harden, and ensuring that tangential pressure as your structure rises doesn't cause your
uncured bags to ooze.

There are no universal "one size fits all" answers. Your dirt, its clay content, your region's climate & humidity, your prowess with your
tamper, your speed of construction - all these & more can impact your results. Let us know your experiences and/or suggestions.

More:

Leveling: Check your work in all 3 dimensions... is the course running straight (end to end)? Are the bags starting to slant inward
(towards you) or outward (away from you)? If they are, do you really want them to be doing that?

When building a wall, don't rely on just the left-to-right (course) leveling and the back-to-front leveling. Check the wall itself periodically
with a beam level to see if it's starting to cant towards or away from you. If you stay on top of it, you can self-correct with the next bag
(or, worst case, pull the last tamped bag & re-do it). Just don't get ahead of yourself.

Barbed wire: As mentioned elsewhere, start using 12" - 14" wire strips between bags if your wall or structure is above 3 feet.
We recommend two strips of barbed wire per bag. After laying a bag, firmly twist the bag to "seat" the barbs before moving on.

Buttressing: Think of these as reinforcing pillars every 6-10 feet or so along the length of a wall. Don't underestimate the importance of
of buttressing long, high walls, and don't count on a plaster / stucco overlay to give such a wall the significant structural strength you'll
want when the kids are climbing on it. Rule of thumb for buttresses is 6" perpendicular to wall for every foot of wall height.

Burlap bags: Using these bags requires working quickly, under dry conditions, and then plastering them as soon as possible.
It's advisable to utilize a stem wall to raise them above ground level to prevent moisture from wicking up. Being willing to work
  with these parameters will reward you with a structure that you'll know is as natural (and as close to true adobe) as you can get.

Big jobs: Because our New Mexico sun is so hard on our polypropylene bag materials (UVI, or ultra-violet inhibitor, notwithstanding),
it's a good idea to tarp & secure your work as much and as well as possible. Some people spread the work on bigger structures over
  a year or two (also allowing them to spread the cost out). Also, some bigger jobs will call for bigger bags (allowing for better curves);
remember that we can supply pre-filled bags up to 3 feet long. On the other hand, we don't recommend subjecting burlap bags to
weather, insects, etc. any longer than absolutely necessary.

Rendering & plastering: click here. 2006 New Mexico Earthen Building Material Code: click here.