Just as each row must be measured tire to tire to make sure it remains level from end to end; so too does the wall need to be measured from the ground up to the top, and backwards.
In the latest style of Earthship (the Global Model) the retaining walls would stagger or ‘batter’ on a slight angle in towards the berm, for structural integrity. That is to say as each layer proceeded higher than the last, it was no more than an inch to an inch and a half pushed backwards from the one under it. Once again a level and measurement let us know if we were veering off course.
After the first row of tires went up and was ascertained to be flush with the initial line and level to each other…
…a horizontal plumb line was run (tacked) from each of the opposite end tires just before the wing walls started curving off to the side. This provided an excellent point of reference for the second row going up.
Using a level to touch the string on the first course of tires, and a measuring tape set perpendicular to the level the distance between rows could be read.
So long as it was 1 to 1.5 inches back from the layer below, all was fine. If however it was under or over that 1.5inches a bit of muscling was required to push or pull that tire back or forwards into the appropriate spot. That sounds easier than it is. Once a tire is pounded it becomes a dense 250 lb brick so there is no shame in sitting on your butt and using your leg muscles to maneuver it into place., at least that’s what I tell myself.
Image credits: Monica Holy