I am new here and am excited to find all the great information you have available. I would like to construct a fence that goes around my back yard. I want the fence to be a foot thick and 6 ft tall and run for a length of 58 ft in all. I have no idea as to how much of everything I would need. I will be using my own soil but it is very sandy with almost non existent amounts of clay. How much clay, soil, and straw will be necessary to complete this project? Just a guess is all im asking for. Thanks so much I appreciate your time.
Others are sure to add there views...
I am always a tad reluctant to get into mix ratios for cob without seeing what you have. Sand to Clay ratios can vary depending on what you have 2:1,2:2, and 3:1 are some folks use, it all depends.
You have 350 to 450 cubic feet ( 6 x 58 = 348 ) but I would recommend the wall be wider at the base and taper to your top.
I also only facilitate "earth walls" that are roofed, as you would see them in Asia. There is no reason to do that hard work and not protect the wall. If you live in an arid environment, then it become less critical.
From doing a soil test with a jar I have sandy loam soil. The clay layer was all but non existence aside for a few trace particles that didnt form a solid layer. I appreciate you calculating the volume for me but wouldn't the quantity vary between wet compressed cob and loose dry materials? I live in Amsterdam Netherlands and this city was pretty much built on water so I imagine that is why the clay levels arent there. Perhaps if we took the soil part out of the equation and assumed I would be using purchased sand and purchased clay what would be a correct ratio for that? I have seen people say 50/50 while others say 3 parts sand to 1 part clay. I can understand being reluctant to give ratios, but Im just asking for opinions. I will be sure to do my due diligence and research fully before I act and I can assure you I'm not going to come back screaming and yelling if I messed something up. Naturally, I can respect your choice if you feel there is not enough information for you to give an answer your comfortable with. Thanks for your time.
Glad to know where you are. I normally work in metric so it will be easier to say you need ~9.85 cubic meters of material for the wall volume described.
If you want a Cob wall just because you want to try it and like the aesthetics of it, then go for it other wise this may not be the most cost effective choice for you to build with.
I appreciate you calculating the volume for me but wouldn't the quantity vary between wet compressed cob and loose dry materials?
No, not for all practical purposes, as the volume is pretty set metric, and Cobb by it's nature is a compact, dense and compressed material. Even if you had been considering one of the alternative "clay straw," "clay chip" or other "low density" Cob matrix, the calculated volume would be the same for design/build purposes.
... what would be a correct ratio for that?
This would still depend on the clay-sand type and a few other factors. That is why we do "test batching" to work these details out beforehand. That way when we begin the construction process we have the correct matrix ration for the Cob and any other factors worked out.
I can understand being reluctant to give ratios, but Im just asking for opinions.
Perhaps others will be more detailed, however when you have been doing this as long as I have, you know from experience what is the appropriate amount of detail to give, before it can become a "misleading guess." You have to do more testing with the materials you have.
Good luck, and keep us up to speed with your project. We would love to see photos!