“Alternative” Interior Wall Finishes

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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12 Responses to “Alternative” Interior Wall Finishes

  1. Avatar
    Terry Mitchell Fri, July 11, 2014 at 11:07 am #

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

  2. Avatar
    Andrew Morrison Sun, July 20, 2014 at 8:50 am #

    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.

  3. Avatar
    Mark Sat, October 4, 2014 at 8:14 pm #

    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!

  4. Andrew
    Andrew Sun, October 5, 2014 at 12:03 pm #

    Hi Mark. Thanks for your message. The shower backing (metal roofing) should be spaced away from the bales about an inch after the first coat of plaster is applied to allow for the wall to “breathe” properly. I am not sure if the authors of comments receive an email. I will send you a copy of this reply in an email. If you get two, then I suppose that means they do. 🙂 I’d love to know if that is indeed the case.


  5. Avatar
    Colleen Sat, February 20, 2016 at 7:27 am #

    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 the tile are staggered, so making the different sides come out even on the outer edge is not a problem. I want to try to do the same thing.

  6. Andrew Morrison
    Andrew Morrison Wed, February 24, 2016 at 11:46 am #

    I agree with you Colleen. I love the gentle undulations of bale walls and the curves at openings.

  7. Avatar
    Colleen Wed, March 22, 2017 at 12:32 pm #

    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 thinset? I figure the bottom part of the window opening needs to be strong in case someone tries to sit on it, so two layers of diamond mesh would be a plus anyway.

  8. Andrew Morrison
    Andrew Morrison Fri, March 31, 2017 at 7:46 am #

    I have to admit that I don’t know the answer to this question as I don’t work with earthen plaster that much. I am a lime guy myself. With lime, you can apply the tile directly to the scratch coat with your mortar. You might connect with Athena Steen at the Canelo Project and see what she has to say. She is an expert with earthen plasters and artistic detailing.

  9. Avatar
    Gordon Veitch Fri, October 16, 2020 at 5:25 am #

    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?

  10. Andrew Morrison
    Andrew Morrison Fri, October 16, 2020 at 8:03 pm #

    Hi Gordon. Thanks for your message. I have never put drywall on the interior of a bale wall, so I don’t have any information to offer you on that one. It would be very difficult to do as you won’t have points of attachment with sufficient spacing for the drywall. If you added those, you would have a LOT of notching to do on the bales and your entire build process would be much slower. Further, you would lose the feel of the bales entirely. If you are after a drywall finish, you’d be better off using high-efficiency, double wall framing with natural insulation. Cheers.

  11. Avatar
    Janice Darling Wed, March 31, 2021 at 10:33 am #

    We built our strawbale home 20 years ago and sprayed on 3 coats of mortar over stucco wire. We have hairline cracks inside that we need to fill. The mortar walls were painted with milk paint. So any repair will need to accept milk paint. Any info on how to repair the cracks is appreciated.

  12. Andrew Morrison
    Andrew Morrison Wed, May 5, 2021 at 9:31 pm #

    Hi Janice. I do not work with milk paint, so I am not the expert you are looking for on this question. Hopefully someone else on this thread can help you. If not, you may want to reach out to the Steens at the Canelo Project to see if they can help. They work with earthen plasters and I believe they have extensive experience with milk paints as well.

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