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April 26, 2010 (updated August 2, 2011) - In his books Michael Reynolds recommends a number of techniques to fill spaces between the tires. In addition, he also pays attention to the end blocks of tire walls. 

At first he recommended wooden blocks for filling spaces between two tires and making the end blocks (How to build your own. Vol I). A few years later he introduces 2 new techniques in Earthship Vol III. Concrete spacer blocks and rammed earth spacer blocks. Let's take a closer look at these 3 techniques.

Wooden spacer blocks:

In this technique the space between the tyres is filled with a wooden block. This should be thoroughly impregnated and wrapped in two layers of 0.15mm plastic, to prevent moisture from entering the wood. The block is kept in place by 2mm steelwire that's stretched around the other tyres. This technique can also be used for making end blocks.

Concrete spacer blocks:

In this technique you use fine chicken wire which you nail on both sides of the tyres in such a way that no concrete can escape. Then you place cardboard against the inside of the gauze. This is also done to prevent the concrete from leaking out. After this you fill the space with a mixture of 3 parts cement, 4 parts sand and 5 parts gravel. This technique can also be used for making end blocks. Michael Reynolds recommends this technique in case you want to build a 2 storey earthship

Rammed earth spacer blocks:

In this technique you nail fine chicken wire on both sides against the tires. On the inside you fill it with 2 layers of 0,15mm plastic. After that you can fill it with earth and pound the cavity, the same way as you would fill the tyres. This technique is not suitable for making an end block. Michael Reynolds recommends this technique to be used not higher than 5 layers of tyres.

In all techniques, it is important to fill the spaces exactly as high as the rest of the wall and that the the top of the wall is level.

Cement is a kind of material that makes quite a carbon footprint. Another disadvantage is that you must wait for a night before you can proceed with the next layer. Hence an alternative is desirable. Apparently more earthshippers share this view because there is an alternative, the half tire.

In the past, I encountered this concept on the website of Michael Shealy. This inventive man (also an architect) tried the technique of working with half tires on the walls of a goat shed which he was building.