11.19.2011 Herb Spiral Cement Plastering

This week, we continued the construction of our herb spiral. CalEarth gave us a recipe to cover their earth bags. We modified it slightly by substituting one part earth with aggregate sand.

It was suggested to cover in multiple layers. Therefore, we will be continuing plastering over the next few weeks.

Note: We highly recommend that small batches are made, since the concrete sets quickly.

Plaster Mixture:

  • 7 parts Clean Earth (soil)
  • 1 part Aggregate Sand
  • 2 parts Dry Portland Cement Mixture
  • Cement Coloring, like Iron oxide (optional)
  • Water

Plastering Steps:

  1. We dug a few feet down where we were able to dig up soil that was relatively free of large organic material (mostly sand and silt). We used a cup to measure out the earth.
  2. We measured out the necessary sand and mixed the dry ingredients.
  3. We slowly added water until the mixture formed a putty consistency.
  4. We finally added some coloring (brick red).
  5. We started filling in the gaps and joints of the earth bags.
  6. We formed a thin layer around the bags.

Bare Herb Spiral

Clean Earth

Add Water

Add Coloring

Mix it


Filling in the joints

Group Plastering

First Layer
Courtesy Jason Carman