Matt River

As regards the finish coat for a floor it does not seem like straw would not work very well if a smooth surface is desired. Also makes it a bit trickier to get a "pour" or leveling effect if the straw is long-stemmed. Manure is referenced by some cob manuals for both strength and stick, this would contain smaller fibers to allow a floor finish. My own floor systems have straw in them but I am building on a very well-drained site over large amounts of gravel.

To add to the comment above, think of how much longer a clean, hand picked unwashed egg will keep compared to the factory eggs that are dunked in foul water by the million, seriously, 50 or a hundred gallon tanks washing hundreds of thousands of dirty cage eggs. Store potatos and onions? With the wonders of neutral atmosphere supercooler warehouses, your commercial produce will be dead when you get it, improperly handled and preserved to boot. My potatos and onions not only taste way better, they keep for, oh yeah, around 10 to 12 months compared to under two weeks if you are lucky for store garbage. Ever think about all of the potatos and other root crops grown in the chemical soaked soil sprayed on, say, they corn rotation, the year before? Do not eat that. Ever.

Oops maybe I should have said, functional cob, not good cob. But why not experiment? Lambswool? seems too oily but... Oh, how about barber shop trimmings - easy to get some places, and human hair is really strong.

Myself I would not use foam against earth in any situation I can think of. My exceptions would be making a homebuilt cooler with sprayfoam - very efficient. A local peach and plum guy brings his stock from colorado and georgia up here to south dakota in a 1/2 ton with topper, interior of topper sprayfoamed with bubble foil baffles, inverter, mini ac into custom slide out, coolbot. I would also consider foam as a great way to insulate and utilize a grainbin for a home or shop, but in that situation (interior foam spray and then stucco inside a reclaimed bin) a whole house air exchange system would be desirable in my climate.

I think that there are even many other potential odd materials that will make good cob. Yak hair, yucca fiber, lambsquarter fiber, long strip pounded bark (oak?), palm leaves, canes or reeds, and pretty much any other fiber if you were somehow in a survival or extreme remote situation (jungle, mongolian foothills, pacific island?). A material I have used was whole entire western red cedars stacked above a no-straw cob mix, laid on gravel substrate. Stacked more cob on top of the brush. Ag building so why not try it. Maybe after a while I will dig it up with the skidder and see what transpired (they were still a bit, um, green).

That sounds like a book I need to have, thank you so much!

Mandan and Hidatsa earth-lodges are also a great place to research.

Morrollan pit houses are a great place to start. nothing showed up when I tried to search the net on them, but they are clearly illustrated in in several of the north american culture books. In "Home Work" by Lloyd Kahn there is a home based off of the kiva, very simple design, page 193. Pages 194-5 illustrate a great variety of indigenous housing in North America.

If you are using shutters, you may be able to pour the cob or at least have the mix much wetter than freestanding type. I have been thinking of building a gravity placement box with a 4" tube drop out of the bottom and trying to pour some cob between pallets as a rapid way to build smaller structures.

And drying time will not be an issue around a woodstove, normally it is a function of thickness and ambient humidity, you can use heat to dry.

Supposedly the more sand in the ratio the stronger the cob will be. One or two dump truck loads of good clay or subsoil would get you going and provide enough "stick" for many times that amount of sand. Another, possible crazy option, it to somehow pulverize shale rock to make the mortar constituent. Good luck!