Tire Bale Construction

TIRE BALE Construction Information

To start with the most often voiced concern; that the bale will deflect when used as a structural element, much like any other piece of rubber. This is true, they will deflect, and the tests have proven it so. However, they have been "deflected" considerably to become "bales" in the first place, and the load required to deflect them further than is acceptable (more than your house will ever weigh), is roughly 1/20 of what has been called a "failure" (150,000# on an unsupported bale; usually when a wire breaks). In other words, your house will NEVER exert that much load on a tire bale wall used as a foundation wall. Also, a steel reinforced concrete bond beam is poured in-place on top of the tire bale wall, to distribute load of the roof framing and possible loads placed on the roof.

What's more, all tests (to my knowledge) have been run in the single-bale or single-stack of bales mode. These tests (and results) do not reflect the true usage/deflection of the bale in practice (constrained by other bales in the wall).

The picture at the left illustrates in a rather low-tech way, that the bale is VERY sturdy. Note: a stack of bales, ten high, covered by local earth distributed by a 70,000# front-end loader. The bottom bales show no apparent compression or effect of bearing that load. I've measured them and there is little (1/2" or so), if any measurable difference between the bales at the top of the stack and the ones at the bottom. This being under a load of more than 9 tons each (bales constrained by stacking immediately adjacent to each other (as in a wall). The bale at the bottom is bearing more than 720#psf with little measurable deflection.

Numerous independent tests have been run to determine the ultimate deflection characteristics of the bales and none has been found. In other words, there is no significant failure mechanism of the tire bale, regardless of pressure. It just keeps deflecting, the more load is applied (tests being conducted in the free, single-bale state). In the restrained state, as in a wall or stack, as shown at left, it would be significantly more pressure resistant, beginning to resemble a 'hydraulic' resistance.

Here, an explanation is given for results of a study of tire bale insulation by Colorado School of Mines, by Leonard Jones, Registered Professional Engineer, State of Colorado:

"The Colorado School of Mines study that we have discussed predicts that the thermal conductivity (U) of tire bales can range from:

0.120 - 0.124 Btu / hr ºF ft

Which converts to an R-value range of 0.694 - 0.672 per inch, or a total R-value of 40.0 - 41.6 for a 60" tire bale wall. This is a far cry from the undocumented claims of R-120 for the same thickness, but it would nevertheless equate to approximately 11.75 inches of fiberglass batt insulation - about what you could put into a 12" thick stud wall... which is about 3x as much insulation as goes into a standard 4" stud wall...very good wall insulation by conventional standards. This material should yield super-insulation-like performance if the entire wall is assembled and completed properly from interior to exterior...

Moreover, the tire bales also have a predicted Specific Heat (Heat Capacity) of 0.18 Btu / lb ºF. This compares favorably with other common thermal mass materials like sand (0.20), stone (0.20), and concrete (0.15). So, the heat storage capacity of the tire bales in a passive solar house should be excellent as well. For the house Mikey mentioned in a recent e-mail, the tire bales alone - at a 10ºF temperature drop should have a storage capacity of:

130 bales * 1T/bale * 2000 lbs/T * 10 degF * 0.18 = 468,000 Btu

Nearly half a million BTUs is a considerable amount of heat! The interior plaster will add even more heat storage... So - perhaps it is possible to have one's (thermal) cake and eat it, too...!! The tire bales should provide excellent insulation - and - provide good heat storage as well. The price one must pay for this, of course, is the massive thickness and weight of the tire bale wall." ... Thanks, Leonard.

For more information (118K .PDF file) on residential building with tire bales see this paper: "Building With Tire Bales - Addressing Some Engineering Concerns" by Leonard Jones, P.E.

Beyond that, there are some limitations to the use of tire bale walls in residential construction, as I see them: 1) Your site must be within unloading distance from a road large enough to accommodate a semi-truck & 54' flatbed trailer. 2) A cost to transport the bales can become significant. At 25 bales per load, calculate distance from the nearest tire bale supplier's location and your site location in miles, times the going rate for over-the-road flatbed trailer haulers per mile rate ($1.35 - $2.70). As you can see, these rates can fluctuate wildly, depending on the demand for flatbed trailers, at the time. 3) Single story structures, although bales can be stacked four-high (10' high) and hold the weight of a roof without a problem. Single story residences are recommended primarily for passive solar function reasons (heat rises into upper levels leaving lower levels cool). 4) Your lot must allow for the 5' thick wall that is created by the tire bales.

Once you get past these, there is NOT a better, less expensive, eco-friendly way to build a 5' thick wall. An average sized tire-bale house will remove 15,000 tires from the ever growing PILE. Beyond that, a passive-solar efficient design will save billions of BTUs and millions of kilowatt hours NOT created with hydrocarbon fuel, in it's lifetime.