So I have to decide how we are going to plaster the outside of our straw bale house. I mean, I have to decide now. Or at least before I submit our revised plans for review. For some reason details like that have to be figured out before we actually start building, so say the building officials.

There are basically three ways you can plaster the exterior of a bale house: cement stucco, lime stucco, or earthen clay. There are lots of arguments for and against each one and lots of people have done thorough comparisons. Sometimes it can even feel like a religious debate within the bale community. I don’t want to get into all that, I’m just trying to work out what we’re going to do with our house.

Our building officials nixed earthen plasters alone; they have to have some kind of stabilizer like lime or cement. Unstabilized earthen plasters are the least durable when exposed to weather and require more upkeep. Somehow that’s not OK with the building officials, even though many historic adobe buildings (and many extant bale buildings) have unstabilized earthen plasters applied that are holding up fine… with proper maintenance. I suppose the building officials are concerned that whoever occupies the structure may or may not perform the proper maintenance and so the plaster would fail someday, and the insides of our bale walls would turn into a mushy composted mess. I’m not sure I understand that line of reasoning since code-compliant building systems fail due to human stupidity and neglect all the time. But it’s the only thing I can think of.

That leaves lime or cement stucco. For the longest time I have had “lime-stabilized earthen plaster” written on the plans. It’s cheap, environmentally friendly, doesn’t require reinforcement, uses mostly local materials, and can be applied with local unskilled volunteer labor. It’s fun to play in the mud. Only now I am having some doubts.

Doubt #1: Part of the house is elevated as much as six feet above the ground. Meaning the 8-foot bale wall to be plastered is between 6 and 14 feet up at one corner, and the ground all around the building is sloped. Which means I would have to figure out how to get unskilled volunteer labor up off the ground at various points around the building… up to 10 feet… safely.

Doubt #2: Our house doesn’t have a continuous wraparound porch, and the side that will bear the brunt of the weather will be rather exposed for a while until some vegetation matures. That also happens to be the corner 6′ up in the air. So the point that will take the most punishment and require the most maintenance is also the hardest point to reach.

Doubt #3: I have no idea how to get lime and clay to play well together. It would take a lot of experimenting. I am not sure how unskilled labor plays into the lime part, since lime is caustic and can be difficult to work with. I am sure in time it wouldn’t seem so mysterious, but most folks around here use cement stucco so the brain pool is smaller when it comes to skill with lime.

All of these doubts would be put to rest with cement stucco. Here’s why: with cement stucco, a crew would come out and basically spray stucco over the whole building. They’d do it in a day. Getting 6′ up in the air safely is their problem. The cement would last 50 years or more with no maintenance. I wouldn’t have to worry about learning anything about lime because nobody would be using it. Sad, but terribly convenient.

The greenie in me chafes at the idea of cement stucco. It’s a high-embodied-energy material. The cheapskate in me also chafes at it, since I’d have to pay for cement and the labor to apply it. The traditionalist in me chafes, since lime is a wonderful traditional material that has been lost to most of us. Cement stucco is also pretty lame in terms of community outreach. Whoever heard of a cement stucco plaster party?

But my inner pragmatist tells me I won’t really want to spend the time maintaining a clay plaster (even a lime-stabilized one), and I really don’t want the liability of someone falling off scaffolding when they’re ten feet off the ground with a bucket of mud. And it would be really nice to have the house stuccoed and done with in a day.

A compromise could be to use lime-stabilized earth where people can reach it, and cement where people can’t. It would be a challenge to blend them and the expense of hiring a crew to do one corner is probably not much different than hiring them to do the whole house. It’s just not a big house.

Regardless what we do on the outside, we are definitely using unstabilized earthen plasters inside, except in wet areas (like the shower). Since it’s inside, it’s really easy to get a bunch of volunteers in there to throw some mud around. Yay, mud! So using cement outside isn’t a total loss.

Conclusion: I still don’t know. But I had better, and soon, or we won’t be getting a permit!

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