How to pound a tire:

The pounded tire is the basic building block of the Earthship.  Tires are used because tires are generally a one use item and then discarded.  The Tire Broker told us that they get about 1500-2500 tires a day from the Colorado Springs area, which is about 500,000 people.  There are other uses for tires (they are now being burnt for fuel, added to asphalt and more).  The supply of used tires still far out weighs the demand. Essentially, the tire has become a natural resource.  In the building process, it has ideal characteristics: it is cheap, requires no special skills, doesn't require years to grow, and will never rot out or decompose.  Once it is pounded, it becomes a solid brick.  Here's how:

Step One: Place the tire where it needs to be. Once the tire is pounded it weighs about 300 pounds, so it is VERY hard to move.  Trying to lift a tire into place will break up the compacted dirt.  Furthermore the tire takes the shape of the space beneath it: it won't fit anywhere else!

Step Two: Put cardboard into the tire. This helps to hold the dirt in the tire while it is packed.  It is not critical on the ground course, but it keeps the dirt from falling out on the rest of the courses.  We tried to find waxed cardboard because it cannot be recycled.  We didn't have much luck.  The next best thing is to find cardboard that is on it's way to the landfill instead of the recycling center.

This is mostly household trash, and requires a lot of "dumpster diving." Our most lucrative cardboard resource was going to the grocery store early in the morning and taking their boxes.  Once we had a good stockpile, we collected boxes at work.   The cardboard is a temporary detail and is not a factor in the longevity of the house.

Step Three: Fill the tire. It helps to have the dirt piled very close to where you are pounding tires.  Each tire takes about three wheelbarrows of dirt.  As one person shovels dirt into the tire, another should shove the dirt into the casing.  The more dirt you get back inside the tire, the less you'll have to pound it.

Step Four: Pound and fill. Grab your sledge hammer and start swinging.  Move around the tire so that all areas of the tire are pounded equally.  The other person continues to shovel dirt into the tire. Keep pounding.  Pretty soon the tire starts to swell.  Keep pounding and shoveling.  When the casing is hard and there are no soft spots that part of the tire is finished.

Step Five: Tamp and level. Once the tire casing is hard, tamp the middle of the tire some and check the level.  The tire should be close to level in all directions.

The most important direction is "inside/outside": you don't want the tire to lean either towards the inside or the outside of the room.  Tire to tire level is important, but can be fixed by the next course of tires.  If the tire is a little high, you pound it back down by hitting the casing with your hammer.  If it is low, pound the dirt on that side some more.  Once the tire is level, tamp the center of the tire very well, check the level again and you're finished!

Step Six: Get another tire. Repeat steps 1-5.

The Earthship Books say that it should take between 5 and 20 minutes to pound one tire.  Our fastest time (my wife and I) is about 20 minutes.  Maybe we are too careful, I don't know. I wish I could do it in 5 minutes!

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