“Alternative” Interior Wall Finishes

Written by Andrew Morrison

Three people plastering a straw bale houseI was recently asked about using different finishes for straw bale walls on the interior. I’m very often asked about using different exterior finishes, but not as often does the topic of interior wall finish come up. Of course, the type, texture and color of plaster is always in question, but more rare is a discussion about using metal panels as a wall finish, or perhaps drywall or even tile.

The answer is that yes, these things can be done; however, “is the amount of extra labor worth it to you?” may be the appropriate question to ask yourself. Keep in mind that straw bale is an organic building material. Where this is most obvious is around curves by windows and doors. At every workshop I teach, people ask me about making a template to measure each window well with to make sure all of the window curves look the same throughout the house. Possible? Sure. Plausible? Not really.

The fact of the matter is that each curve will be slightly different. That’s part of the beauty of building with straw bales. So now consider how you might finish an 18″ deep window well that has a natural, undulating curve to it, slightly different on each side of the window, while using metal panels. How do you attach them to the house? How do you adjust for the irregular shapes within the window well?

You can see where the difficulty comes in. The same is true for any material you use that is rigid and “unforgiving” to uneven sub straights. The key is to provide backing that fully supports the material in mind to ITS specifications. This means that you may have to insert framing to support the material every 24″ on center, or provide for nailing on a specific pattern. You’ll need to weigh the pros and cons of each finish you choose and see just what is worth your efforts.

I have seen corrugated metal roofing used in shower stalls and in straw bale barns to great success; however, would I do an entire room with that material? Probably not. I think for specific spaces that require something like this, it is worth it. If you want your walls to look like drywall on the inside, then I suggest you build with drywall, and forgo the straw bale infill, or at least create a hybrid installation system that will eliminate all of the “extra” framing to be notched in to the bales, post stacking.

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Thanks for the great information ! What is the best way to secure the plaster on the interior rounded overhead of my windows?

Thanks Terry. You have to apply a LOT of pressure when doing this. Run the trowel back and forth across the curve from side to side (with the trowel perpendicular to the curve) and push hard as you apply a thin layer of plaster. Once that plaster takes hold, then you can add a little more thickness to it. You have to start thin and make sure you are anchoring it to the straw first.

Won’t the metal (“for the shower”) stop the straw from breathing (= bad, mold, …)? Unless you make it a separate cage of course… What do you think.

P.S. Does this website send replies to this question to my email? Would be a great feature!

Speaking strictly for myself, I can’t imagine wanting straight edges on the windows. The straw houses I’ve seen that are like that are not nearly as attractive as the rounded ones. I *want* lumpy walls, that’s half the attraction of building with straw! (I will be starting my house this spring.) The most attractive window finish I’ve seen is at the house of one of my neighbors. His rounded window enclosures were finished with 1 inch tile. Because of the variation in the shape of each curve, the tile has a sort of undulating organic effect; the outward edges of… Read more »

Hi, I’m back! My house is coming along. I’m using earthen plaster inside and out. I’m shaping the inside of the windows with cob rather than stuffing loose straw behind mesh, which is time-consuming, but I have time, and it might end up being the same amount of work as trying to plaster over loose straw. I will still put mesh over the slip coat/cob for the browncoat. My question is: how do I attach the tile? Will thinset stick to clay? Could I embed a second layer of diamond mesh in the top of the browncoat to anchor the… Read more »

Hi Andrew,

If you were going to put drywall on an interior straw bale wall would you want to avoid putting in a vapor barrier to prevent moisture getting trapped in the wall cavity or would you put in a vapor barrier and have the straw bale wall dry strictly to the outside?