Earth Plaster

Rough Earth Plaster for Cordwood Wall

Purpose

To give the walls a nearly smooth surface in preparation for final plaster. Final plaster does not perform well over gaps deeper than 1 inch or shallower than 1/4 inch.

Ingredients

(same ingredients as cob) 5 gallons of submerged mud from the duck pond 5 gallons of crushed lime half a wheel barrell of straw (fluffed not compressed)

Making the Plaster

Chose a work area that was flat and shady Cleared work area of large rocks and sticks Spread tarp Dumped mud and lime on a tarp Stomped and rolled the mixture until it became homogenous

Stomped the sand and mud together

When the pile became flat like this, it was time to roll it over.

Rolled the pile by pulling the tarp

When the act of rolling produced a nice "burrito" shape, it seemed to coincide with the mixture being homogenous.

Added straw gradually as I continued to stomp and roll

Covered the plaster with the tarp to keep it fresh while I prepped the wall

Note: I kept the mixture as dry as possible. But at one point I had to add some water because it got so hard that I couldn't stomp it

Preparing the Wall

Determined which ends to keep visible (keepers) and which to bury Scraped the keepers with a trowel Brushed the keepers with a wire brush Oiled the keepers with linseed oil Pre-Soaked the wall heavily with a spray bottle (Critical) Filled a five-gallon bucket half full with plaster and brought it over to the wall

Plastering

My understanding is that difference between "cob" and "rough plaster" is how they are used. When used structurally it is referred to as "cob" and when used cosmetically it is referred to as "rough plaster".

Most important factor: Spray as you go. In between each handful of plaster I re-soaked the wood and cob in the immediate area where that particular handful of plaster would be placed.

The motions necessary to work the plaster onto a vertical surface naturally leaves a smooth surface. I left dibbles in the surface of the plaster so that the final plaster will have plenty to grab onto. Dibbles.jpg

Objectives: To fill any gaps that were more than 1" deep To cover all the rounds except the keepers To keep the rough plaster 1/2 inch back from the keepers' edges so that the final plaster will finish flush Keepers edge.jpg

Recommendations / Suggestions / Ideas to try

Select keepers well in advance and finish them with lacquer before attempting any rough plastering. Lacquer is better than oil because it protects wood against boring beetles, does not have to be re-applied every six months, and provides a smooth surface which is easier to clean. Dirty keepers are hard to clean and often too difficult to clean completely. Choosing the keepers and lacquering them before plastering could help with these issues.

Ask lumber companies for the tarps that they throw away every day - these are great for stomping plaster

In general, choose keepers based on how far they stick out. Keepers that protrude farther than the surrounding rounds are the easiest to plaster around.

Finish Earth Plaster to cover interior of cordwood / earthbag structure

Attempt 1

-Travis Toon

Ingredients

1500 ml sifted soil, hydrated to a gel/paste like consistency. Gathered subsoil (16 inches deep) from near the well. Hydrated the soil and sifted it using 1/8" screen.

200 ml fresh cow manure. So fresh there was still steam rising off the top. I am told freshness is not necessary, but that composted manure is worthless.

180 ml wheat paste. Added whole wheat flour and cold water in a pan. Stirred together well. Then heated until pasty. Add immediately. I ate the leftovers which were quite tasty.

Handful of micro straw. This particular grass was found above the tent site 10-15 ft short of the property line near the goat fence. Chopped into 1" lenghths. Did not include roots or seed stalks.

Procedure

Mixed together above ingredients by hand until homogenous.

Chose an area that was relatively smooth and void of large holes. Areas with holes much larger than 2" wide by 1" deep should probably be prepared with a rough plaster mix, i.e. cob.

Pre-soaked the area to be plastered. Waited 20 minutes for water to penetrate old cob.

Made a slurry. Took 10% of the plaster and mixed it with water in a separate bowl so that it would go on very thin.

Re-wet the area immediately before applying slurry.

Applied (smeared) slurry with hand approximately 1/16" thick.

Applied plaster about 1/2" thick by hand over the slurry. The plaster was very easy to work with.

Troweled the area. The tool for this was improvised from a piece of 6" diameter PVC pipe fitted with a 1" PVC handle.

12 hours later smoothed out the trowel lines. The tool for this was a lid from a medium sized yogurt container. Used a pair of scissors to cut off the outer edge of the lid.

Attempt 2

Ingredients

800 ml sifted soil, hydrated to a gel/paste like consistency. Gathered soil from edge of the duckpond. Since the soild was naturally hydrated, it was easy to sift using the 1/8" screen.

800 ml sifted sand. Used the same 1/8" screen for sifting.

200 ml fresh cow manure.

180 ml wheat paste. Added whole wheat flour and cold water in a pan. Stirred together well. Then heated until pasty. Add immediately.

Two handfuls of micro straw. This particular grass was found above the tent site 10-15 ft short of the property line near the goat fence. Chopped into 1" lenghths. Did not include roots, but got lazy and let some seed stalks in.

Procedure

Mixed together above ingredients by hand until homogenous.

Chose an area that was relatively smooth and void of large holes. Areas with holes much larger than 2" wide by 1" deep should probably be prepared with a rough plaster mix, i.e. cob.

Pre-soaked the area to be plastered. Waited 20 minutes for water to penetrate old cob.

Made a slurry. Took 10% of the plaster and mixed it with water in a separate bowl so that it would go on very thin.

Re-wet the area immediately before applying slurry.

Applied (smeared) slurry with hand approximately 1/16" thick.

Applied plaster about 1/2" thick by hand over the slurry. The plaster was very easy to work with.

Troweled the area. The tool for this was improvised from a piece of 6" diameter PVC pipe fitted with a 1" PVC handle.