Bond Beam

The idea behind the bond beam is to give the roof trusses a way to attach to the tires. Our bond beam is two layers of pressure treated 2X12's stacked all the way around the building, bolted to the tires with 1/2" X 10" anchor bolts. I did a little research and learned that regular pressure treated (CCQ) lumber is treated with arsnic and chromium. Apparently there is enough arsnic in a 12' 2X6 to kill 250 adults if they were to consume it.  Given the choice, I'd rather avoid those kinds of poisons into my home.  It's probably safe enough to use...decks everywhere are made out of the stuff...but I imagine these huge pools of arsnic wherever the lumber is pressure treated.  I searched around and found a place in Boulder Colorado, called Eco-Products (www.ecoproducts.com) that sells ACQ.  It's treated with a copper based treatment and is supposed to be much less toxic.  The lumber cost a little bit more, but I think it was worth it.

The first step for the bond beam is to make sure everything is level.  We added a little dirt and tamped it well.

Then we placed the boards for the first layer where we wanted them and drilled a hole to accept the bolt.

We then pulled the first layer and laid two layers of six mil plastic under the boards to protect them from the dirt and cement.

We bolted the first layer down and started the second.  Anywhere that there was a break in the first layer, we made the second layer overlap each board by about 14" to make the two layers into one continuous beam. Using 16 penny nails, we attached the second layer.

For the header over the window in the middle U, I glued and nailed seven 2X8's together to make one solid beam.  We set it in place, then drilled three holes all the way through the beam and pounded a three foot piece of 1/2" rebar into each hole.  I bent the top of the rebar over, then cut a piece of 2X12 to fit over the header. On top of that, we continued the two layers of the bond beam

We finished nailing everything down and made arrangements to have the rooms "dug out."  They had collected A LOT of dirt from the tire pounding.  We scraped out the loose dirt in the voids between to finished tires so that it could be taken out with a bobcat with the rest of the dirt.  We were amazed at how much dirt came out of the rooms, and how much larger everything looks now.

With the bond beam finished and the first course of tires visible again, it was time to call for another inspection.  A different inspector is in charge of this portion, but the plumbing inspector, oddly, came with him.

This inspection went very smoothly.  I laid out the plans, the Earthship book and the foundation letter from the engineer.  The inspector was amazed.  All he could say was "Wow." He even asked if he could bring his wife back to show her. It was fantastic. Concrete is next, then the roof!!

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