Tiny Cob Shed beginnings

Hello there Permies. I'm new to the boards and this is my first post/question. I'm from Southeast Pa. I'm still very new to the idea of Cob and am still reading The Cob Builders Handbook and The Hand-Sculpted House. I want to build as my first project a very tiny, roundish potting shed. Eventually, I want to build my own tiny house. First off, I just want to say I've been reading around on the subject on this forum and it seems like its gotten away from being simple and gone towards being so technical. Don't get me wrong, I understand the structures have to stay up. It's just that my mind set is on what people used to do a long time ago and what people do in 3rd world countries where they don't have all the resources that a lot of people on here recommend. I'm willing to work hard but I want to keep it simple. Anyway, on to questions about my plan....The shed on the inside will be 4' x 4' x 6' tall. Since it's so small how deep do I have to make the rubble trench foundation? Whats the thinnest I can make my walls? The roof will be held up by some old 2x4s I have laying around. Here's a picture of my dirt test jar from the only place I have to dig on my property. It looks to me that I don't have enough clay. What do you think? I would love to see some pics of any tiny sheds that people have done on here if you want to shoot me an email. Thanks so much!

Hi April,

I will try and be encouraging, but straightforward at the same time. Adobe, Cobb, Bousillage, or any traditional Architectural permutation that has been around for millennia, is going to be technical, in some cases very technical. Just because a craft is done by indigenous cultures around the globe, and has been for millennia as well, does not mean, necessarily, that is always simple or easy to perform. I came to this "mud architecture," as but one facet in a broad range of traditional life skills; in this case it applies to methodologies in clay infill and mass wall architecture. I was mentored by folks that had been building this way for the norm, not as some fad out of a "new book." Now I don't mean that in a condescending way at all. I love the books you referenced and think this new movement back to traditional methods is absolutely wonderful, but make no mistake by buying into the normative culture around these books (not the authors fault at all) that this work is either easy, or non technical. If you think building your "potting shed," out of cobb is going to be easier than "stick building it," or even a simple "timber frame," of it, you would be mistaken. Cobb is probably the most labor intensive and perhaps in some ways even more expensive, that is if you count your time as having value.

Of all the "mud" methods of architecture, I tend to lean toward cobb infill methods over only pure cobb mass walls. The main reason is the technical aspect of getting a "clay mass" wall designed and implemented correctly to withstand the rigors of time, such as you would find in the Pueblo and Hopi culture (two of the places I learned clay architecture.) Cobb, without internal structure is the most challenging to get correct, and have it be enduring.

As for your jar test, I don't see much clay at all in that sample, and certainly not enough to form structured cobb out of. Can you dig in other locations that presents with a higher clay content? I would also point out that if you are going to go through the effort to build something of any functional size, 2 m x 2.5 m is almost the same amount of work as building something that is 1.5 m x 1.5, so maybe reconsider your design size by making it larger.

Gravel trench or "rubble trench," foundations are great, we use them almost exclusively now when we can't find bedrock to tie a frame into. The width should be a minimum of three times the width of your grade beam wall width and penetrate grade to a minimum of 0.6 m, or to frost depth accordingly. Forst is a bit of a misnomer, when the real problem is water, getting rid of it, and bentonite clays, (which expand just as destructively, or more so than ice.) If the soil under a structure is kept dry you can't have frost issues, because there is nothing to freeze.

Hope this helps and gets you moving to a final outcome,

jay

Hi Jay. Thank you so much for taking the time to give your advice. I didn't mean to make it sound like Cob would be easy or simple. I have to start somewhere right? I'm determined! In fact I'm looking forward to the hard work. I LOVE DIRT! I used to make mudpies when I was a kid. I never knew the mudpies would come back to me one day. haha. I've been interested in natural building for a very long time and when I found Cob I knew I found what my soul had been looking for. I live in an area where the houses are all connected and my yard is postage stamp sized. I don't intend on getting a permit...Damn the man! So I was trying to keep it small. I will widen it tho. My son is a Wwoofer on a farm not too far and has told me that they have clay dirt. I will be giving some of their dirt a new home and purpose. You didn't advise on how thick I HAVE to make the walls? As far as my time having value....I cant put a price on finally finding myself after so many years. This is a spiritual quest for me Jay.

Hi April,

Wall thickness depends on approach method. I can't be there with you so when I give advice over the net, I am conservative. Others here may venture their thoughts and opinions, but I do not condone cobb mass wall architecture in general and definitely not for the beginner, I want to see a matrix either in the wall or outside of it, as part of the supporting armature of the architecture. The armature (frame work) can be as detailed as a timber frame or as simple as some old 2x material, which would make the walls a little over 150 mm thick when all wall rendering (plastering) is complete.

The most enduring cobb structures are the ones that have some "bones" in them. Yours can be as simple as stout sticks lashed together, kinda like a giant bird cage or basket. So for your project, plan on a wall that is at least 150mm thick.

Thanks Jay. I will think about it and let you know how it's going.