Straw Bale Patio Walls

I was recently called out to consult on a straw bale patio wall that had failed miserably in its duties as a wall. Though I was amazed at what I saw, I was not surprised. I was taken aback that this would happen in Tucson since we don't get very much rain; we have actually been in a drought for longer than the existence of the wall I studied.

The top surface of a straw bale wall is very wide and receives a pounding in a Tucson Monsoon rainstorm. I cover the tops of the straw bales walls I build with light weight tarpaper before I put on the lath/wire. Since straw doesn't have the nutrients of hay it isn't as desirable as hay to hungry microbes and critters looking for a free meal, but add water and almost everything is a potential meal for microbes - even metals. The proble with the wall here is it had no moisture barrier at the top of the wall! The rain was driven into the stucco and absorbed by the straw where it was too slow in evaporating.

Using tarpaper or plastic on the top of the wall is very important and here is why: The wide surface at the top of the wall accepts a great deal of rain. The water permeates the sponge like bale, and the water is then trapped under the plaster where air and sun can not help in evaporation. The straw is now wet so becomes food and home to a multitude of microorganisms that thrive in wet environments. As the straw is eaten oxygen is consumed and quickly used up. The environment goes anaerobic without free oxygen, then H2S (hydrogen sulfide gas) is released as a biproduct of the microbes.

Here is a quote from Wikipedia, the free encyclopedia : "H2S, is a colorless, toxic, flammable gas that is responsible for the foul odor of rotten eggs. It often results when bacteria break down organic matter in the absence of oxygen, such as in swamps, and sewers. It also occurs in volcanic gases, natural gas and some well waters.
Hydrogen sulfide is corrosive and penetrates the lattice of some steels and makes them brittle.
Sulfate-reducing bacteria obtain their energy by oxidizing organic matter or hydrogen with sulfates, producing H2S. These microorganisms are prevalent in low-oxygen environments, such as in swamps and standing waters. "

You can see by the corrosion of the rebar that the hydrogen sulfide is very corrosive - the rebar you are looking at is only five years old. Left exposed to rain, weather or even driven into the ground, rebar won't corrode this quickly. Here is the next step in the process: H2S + H20 can cause H2S04 which is sulfuric acid and this is very corrosive indeed! As you can see this acidic environment is not what you want in any type of wall, but most especially straw bale where your armature is surrounding such a soft medium.

Once the water, sulfur and acid had its way with this wall the wire and rebar were all corroded quickly becoming useless. The acid also dissolves the cement. The rotten plaster was like powder and broke off in my bare hand. The solution after the rotting has gone this far is expensive and time consuming. You don't want to be this person. There is no need to be this person.

Solving the problem at the lathing stage is simple, cheap and pain free. Using tarpaper will add decades to the life of the straw bale wall. Now add and maintain a good coat of paint and a straw bale will compete with masonry in its beauty and longevity. Installed correctly straw bale is a good way for a owner builder to get a great looking wall provided some simple, but important techniques are followed.

Stay tuned next time for a newsletter and pictures on why we don't just place cement mixed with sand on the ground, lay some flagstone, and hope it will last... I will have lots of pictures on how NOT to build your flagstone patio; expect a follow up in a couple of years with the dismal results.

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I just finished adding a 30 minutes of video on straw bale patio walls to the Multitorial - also available on DVD. In the video I cover straw bale walls from conception to completed wall. Of course I cover moisture at the top, but even more importantly I cover getting the bales off of the ground in a simple way. I cover some new techniques that I invented in sewing the lath on a wall - it works like a bobbin on a sewing machine and will cut your lath time by 50%… and you don't need any special tools to make it work. Just use your sewing tool and one simple step to save hours of tedious lath/threading time. Also in the video I have some close up footage of plastering tips and tricks - I even used slow motion to demonstrate techniques - that are sure to help you save frustration and back breaking labor.

Of course the videos made the Multitorial much larger so downloading is out of the question and your new upgrade will have to be delivered on CD-ROM. The S&H is still only 5.99 you can go here for an upgrade if you are a current Straw Bale Energy Revealed or Compilation student:

Or here if you would like your first copy:

Love, Light & Happy Building!

Rusty Cline,
President: Monument Masonry, Inc. (dba: MonumentMasonry.com)