Block Placement

BLOCK PLACEMENT

There are many approaches to stacking adobe blocks, however, for the best end-product and speed, story poles are highly recommended. Story poles can be constructed of wood or angle iron and are placed vertically (perfectly plumb is important) at the corners of the building by attachment to the foundation. Angle braces fastened at the top of the story pole and then secured either to the ground outside or to the foundation will keep the story pole plumb. Mason's blocks, made of either plastic or wood, provide an attachment system that allows the builder to slide a horizontal string up the story pole without knots or nails. They provide a perfect guide for the block layers. There is some initial investment of time required in constructing the story poles, but this effort will save more time during construction than it takes and definitely improve the end product.

Ideally, pressed Earth Blocks should be fastened together with exactly the same material from which they are made. If the blocks are 100% earth, then the slurry should be that same earth sifted through a quarter-inch screen and mixed with water to a milkshake consistency. The slurry should be applied to the lower course of blocks as thinly as possible, but with complete coverage. It should never be allowed to become dry before placing the next course of Earth Blocks, as the molecular adhesion sought is dependent upon all the surfaces remaining moist.

This method of block stacking is unfamiliar to many experienced masons who are accustomed to thicker mortar joints. We have the hope that masons will be encouraged to use a thin slurry by realizing the speed with which Earth Blocks can be laid, the significant decrease in the amount of mortar to be mixed, and the superior bond created. If Portland-stabilized blocks are used, again, the slurry should be of like material. It will be necessary to blend from 5-10% Portland with the earth slurry mixture following sifting. An important difference between stabilized and unstabilized slurry is that the stabilized slurry cannot be reconstituted simply by adding water as can the unstabilized slurry. Any stabilized slurry that is not used within two hours should be discarded.

The structural integrity of an adobe building is greatly influenced by the methods used to lay the blocks. Along with the previously mentioned requirement of wet slurry, staggered joints and wall weaving are of the utmost importance. Some codes call for joints between courses to be staggered by at least four inches. Although desirable and code-enforced in some regions of the U.S., it is essential to remember not to have a block joint directly above a joint on the course below. Where walls come together to form a corner they should be woven with alternating patterns as each course enters the corner. This same weaving technique is crucial where interior walls meet exterior walls.

If building with unstabilized earth blocks it is critical to protect them from water. The top of the wall is the most vulnerable. Plastic sheeting can be nailed up to the walls and/or over the walls proving to be a method that is fairly effective. Stabilized earth plaster, troweled on, provides a tighter and therefore better barrier against water damage. A formula for this plaster could be six parts sand, three parts clay and one part Portland cement mixed with water to a plaster consistency.

Earth Block, Inc.

P.O. Box 3605
Pagosa Springs, CO 81147
Jim or Nora Hallock
Phone: 970-883-2456
Email: earthblock@juno.com