by matt walker » Thu Apr 03, 2014 3:36 pm
So, yeah, cob outdoors is tricky, BUT.......
Everything out there that you read about techniques or concepts for outdoor cob are lacking a major factor that we have going for us. Our cob benches have internal heat sources to power dry them. That makes a HUGE difference in what you can get away with, and it's something uncommon so you don't find too many examples to learn from.
So, Rhett, you are in Texas. I strongly believe that you can build yourself an outdoor whatever out of cob, and in a year or two you will know which parts need protection and which don't.
Sitting on cob outdoors sucks, so you will want slate, or tile, or even a wood top, or cushions, or something that keeps your butt from getting a big dirt print, or beer mud, or whatever, on it. So that's a start for the protection.
I did a lot of reading about lime plasters and other techniques (linseed oil, etc.) before playing a lot with the outdoor systems, but in practice I don't think most of those conversations apply. The heating and cooling cycle I'm pretty sure would flake a lime based coating off of the cob over time, and warm linseed oil doesn't sound nice to hang out on or near.
Basically, I think you can get away with a lot of stuff that is not recommended for cob construction when you have a heat source inside of it. Boots are important, otherwise capillary action will couple your cob to the dirt and it will stay living. A roof over it is the best protection, but mine sit unused in our incredibly wet winter and in the spring they are just fine. Wet and need drying again, but they don't melt away or anything. A few consecutive nights of fires and it will stay dry through the summer season, and periods of rain don't bother it and tend to not penetrate very far when the thing is dry and in normal use.