Cob

[Rhett]

So I had my first experience with cob today. Very cool, I can't wait to see what it's like when it dries. I actually made an adobe brick and a pile of cob. I really like the adobe concept. It seems like the cob would cure much quicker. And once dried you can use it immediately or years later. That kind of modularity makes a lot of sense to me. Of course if you want a bunch of curvlinear walls or furniture straight up cob is the way to go. I can see uses for both approaches.

If one of these first test batches proves durable, I am gonna cob the crap out of this stove. I've been reading up on the lime wash thing. First, how cool is that? You are basically building a cave wall! As the lime carbonates in the air it is literally producing a thin layer of limestone. That just blows me away. Graham - you say its the way they do it up where you're from but you think it's a dead end Matt? What's a guy to think?

Oh, my daughter helped me and probably said "this is fun" three or four times. When I said it was called cob it clicked with her - she had read about how they would build cob houses in the Little House on the Prairie books. She never knew what the heck they were talking about when they said they built the little cottage out of cob!

So, good learning and good fun.

[matt walker]

Nice man! Glad to hear you got into it. It is such a great medium, and it is a lot of fun to do with kids. I built a cob wall in my greenhouse yesterday and had a great time as well. I bet your local materials make great cob!

Oh, as far as the lime goes, I honestly don't know. It's been used for centuries (millennia?) for protecting earth structures from the weather, but the part I am unsure about is the heating/cooling cycle of a relatively small amount in a short time that will happen in an outdoor RMH. I honestly don't know how it will work. My fear is that uneven expansion/contraction will create areas where moisture can penetrate and then the same cycles will separate the different layers, but maybe it will be just fine. The real answer here is I don't know. Like I said, I've been doing just fine without any treatment, and I haven't built one outside that I haven't had plans to modify, so I haven't had a need to "finish" one permanently yet. I do think it's well worth experimenting with.

[freedomlives]

I read a bunch on lime last year-- if you want to become a fanatic about lime, buy the book "Building with Lime" by Holmes and Wingate.

We earth plastered the walls in one room, finished by limewash colored with natural pigments. The ceiling got earth and then limeplaster.

I doubt the lime would have a problem with the rocket stove heating/cooling cycle-- though I'll see soon, because I plan to lime plaster mine.

Also, slaked lime can be mixed into the clay to get a harder earth plaster, which is actually what I did in that room, due to having kids, a stronger plaster seemed like a good idea.

[Rhett]

I saw one video where a guy was mixing tallow into his lime wash. He said the tallow underwent a chemical reaction that made the final wash a vapor barrier - water could leave but could not enter. Seemed...dubious?

[matt walker]

I think the lime will be just fine on your indoor heater Andrew, my concern is the varying cycles of outdoor use will make the lime's job extra difficult. I do think it's worth experimenting with for sure.

[Rhett]

Oh no, you can't backpeddle now Matt. You're a lime hater. A limeist. An antilimeite.

[matt walker]

Shhhhhh, I'm earning it's trust.....

[freedomlives]

[matt walker]

I made a video to show you guys how my outdoor system is holding up after a wet winter outdoors. I ramble on a bit, but maybe it will give you some ideas of what or what not to do.

[mannytheseacow]

That's another really helpful video, Matt. It definitely clarifies what is going on there, in that you aren't using a traditional "cob" on cob structure that could slump or collapse in the rain. The structural framework you have is definitely going hold everything together, and you make a good point that it is super-drying itself out on a regular basis. Also pretty cool that it grows things. The moss and bits definitely make an organic feel. Might not be featured in Better Homes and Gardens, but definitely rad for folks like us.

The maintenance is the part I struggle with. I like to do things once and forget about it. Just patching the feed on my indoor stove periodically drives me crazy. Like, if I'm going to keep the materials around I want them to be for building something but just keeping them around to fix something once in a while 'maybe' drives me nuts. It seems inevitably I don't mix up enough, then I mix up too much, then I have waste.... urgh! I like to have something for a purpose or get it out of my life. Maybe I should relax....

It seems you've told me before, but where do you get the glass for the window? Or what kind of glass is it? Also, is it safe to assume that you've got a batch box there following the Peterberg method or is it just a loose facsimile?

Freedom: very awesome information there, too. I'm really interested in what you are doing. Please post some pictures up if you have time. It's such a pleasure to read about something outside of matchstick and gypsum boxes.