Doing some research on earth domes and I’m seeing a new trend, tire bales. These are 5 feet long, 5 feet wide, and 2.5 feet tall. They weigh 2,000 pounds apiece. They are environmentally friendly, being sold for $25-35 a unit plus shipping. I’m planning on using them around the houses perimeter as I feel they are much less expensive and more durable than a masonry wall. Covered in concrete or adobe they won’t be an aesthetic issue either.
I was wondering what your opinion of them would be as a ballistic barrier/wall?
Keep up the great work. – David F.
JWR Replies: Tire bale bastion walls (or even entire tire bale houses) are a viable option, and they do indeed offer great ballistic protection. (Although their irregular shape does leave a few gaps that would have to be “chinked” well with shotcrete.) Tire bale walls will definitely stop all .30 caliber rifle threats and will probably stop .50 BMG or Russian 12.7mm machinegun bullets. But I must mention a few provisos: 1.) The cost per cubic foot of wall is substantially higher than with the usually free for the hauling packed-earth tires (as used with “Earthships” ), and 2.) , Because of the great weight of tire bales, a forklift (or a skid-steer equipped with forks, or a heavy-duty crane hoist) is required. This means that you can work only on a level building site, and, 3.) Unlike Earthship tires, which can be earthquake stabilized with just driven re-bar rods, tire bales must be specially strapped, and 4.) To be fire resistant, tire bales should be encased in adobe, shotcrete, or other masonry on all sides. (Following your link, I found a great series of photos  that show a large tire bale house under construction.)
If you are going to put forth the effort to encase tire bales in adobe to add ballistic protection to an existing house, then you might as well build masonry “planters” that are filled with gravel. Two feet of gravel will stop bullets just as well as a tire bale, and there is no fire hazard.