Darfield Earthship

Progress on the house

Posted on 01. Mar, 2010 by Sandra in Bond beam, Construction, Earthship

I have been busy this week investigating some possible work opportunities so Chris has been working a little on his own.  But this weekend saw us get a fair bit done on the house.  Most exciting, today (Sunday) we started plastering in our first pop cans (during the Canada/USA gold medal hockey game).  I drove the kids to Dad’s to watch it on TV and they gave us cell phone updates as the game progressed.  Yay Canada!

But I digress.  Here we go!

The bond beam form has been progressing…here is Chris bending re-bar for around the corners…

As the forms were leveled gaps appeared between the wood and the tires (caused by the slight out of level of the top row of tires).  We checked the top row last weekend with the transit and there was no more than 2 inches difference from the highest to lowest tire!  Pretty good.  However, we need to fill in the gaps we have so that when we pour concrete, it doesn’t simply escape out of the bottom.  When pouring a traditional footing this is pretty easy; just mash dirt up into the gap.  However, when you are 8 feet in the air and the bottom of the “form” is a round tire, this becomes more problematic. 

We debated about whether we would scab on old wood while we poured, but in the end we’d have to take it off and plaster in between the tires anyway.  So we made the decision to plaster in the gaps on the top row right now, simply to be able to pour concrete (and hopefully not have to redo the work later).

The plaster mix is essentially a cob mixture made up of clay-soil (dirt), concrete-sand and fibre (usually chopped straw).  We found and borrowed, from the library, three plaster books we’d previously read.  The Earthship volumes are not heavy on detail about the plaster so we consulted mainly with The Natural Plaster Book: earth, lime and gypsum plasters for the natural home.  It is excellent.

One of the most important things to do before using native materials in a plaster is to determine the levels of clay in it.  Clay is essential in natural plasters as it works as a binding agent.

So we followed directions on how to determine the clay content.  We filled a quart jar 1/3 full of the dirt we hoped to use as the clay-dirt.  We then filled the jar to 2/3 full by adding water.  Then we shook it.  After 3 seconds the “gravel” settled out.

Chris marked this line and set the timer for 10 minutes.  In the next 10 minutes the finer sand and silt settles.  If the water is still quite cloudy, then you have clay in your soil.  Wait even longer and you can determine how much clay.

This was taken after about 20 minutes.  After the clay settled, we figured we had just under 25 percent.  This is quite high so when we mix our plaster we will keep this in mind (especially for the finish coats where we will be avoiding cracks).

Most plasters call for chopped straw for the fibre content.  The book we read mentioned sheep’s wool as a good alternative!  We still had two bags of wool left over from last year’s 4-H shearing day. I read up on how to wash wool to get out all the lanolin. 

Here are a few pictures of the wool during washing last night.

The house smelled a bit like the barn for a while!

Here we are pulling apart wool into strands so that it will evenly distribute through the plaster. Some of us are happier than others…

Today while the kids were watching the hockey game, Chris and I pulled a wheelbarrow each of clay-dirt and sand to the house next to the cement mixer.  We added equal shovelfuls of both.

After we added enough water to make the mixture “soupy”, we added about half a grocery bag of wool.  This was a bit of an experiment as the directions gave amounts for straw, but not for wool. 

After the wool is mixed in, the mixture was quite thick. Here’s the first handful thrown into the space between tires and underneath the bond beam form.

And after the first can is mashed in…hey!  it looks just like it does in the Garbage Warrior!!!!

Here’s a few in a row…

This is only the first step.  We need to let this layer dry, then wet the outside and do another layer with two more mashed pop cans.  We will do these two steps for the top round of tires so we can pour cement, but eventually all of the tires have to be done.  There are 762 tires in the building so far so that’s a lot of plastering.  Thankfully, it does go very quickly….