The urbanite stem wall is the last part of the foundation. It is what the cob and straw bales will sit on and what will help protect them from moisture. Because we live in a very seismically active area, we decided to use mortar to reinforce the stem wall, rather than dry stacking. The mortar recipe was three parts course sand (taken from this mountain of sand below)...
...and one part portland cement.
We combined these ingredients in a wheelbarrow...
...added water, and mixed aggressively.
Here's Jim cleaning up the mortar with a wire brush on the exterior side of the stem wall.
photo by Nick Gabinet
Here is one section of stem wall nearly finished, at the height of about four courses. The sidewalk chalk was used to mark a line on the urbanite once it was laid but before it was mortared to help in remembering where each piece goes after the mortar is applied.
We focused this early stem wall building effort on the biggest pod since that is the area we'll be focusing on for the upcoming natural building workshop. We want to make sure we're prepared for that, but we still have plenty of stem wall building to go.