Hardwood Floors in a Straw Bale House

Written by Andrew Morrison

Hardwood Floors in a Straw Bale HouseHardwood floors in a straw bale house may not be the most common of floors, but they sure are beautiful. The reason they are not the most common is that most people want to couple the thermal mass values of concrete or earthen slab floors with the thermal insulation values of the bale wall assemblies. This makes sense, but is not always applicable.

For example, some homes are built on raised floor foundations and as such, are better suited for lightweight floors like hardwood or engineered wood floors. Some owners simply prefer the look of wood over slab products, while others find that their physical and/or financial limitations require them to work with wood floors over slab materials.

No matter what your reason for choosing hardwood or engineered wood floors, you will run into an issue that folks who build with slab floors won’t have: edge gaps. It is absolutely essential to leave a gap at the edges of your floor where it meets the wall. If you don’t, your floor will buckle over time as the floor expands and contracts. For this reason, the edge gap is also known as an expansion gap.

For floating floors, it is also required to allow the floor to move as needed to avoid buckling. Be sure to check with the manufacturer specifications for your floor material before you start installation. In fact, I suggest you check those specifications before you start your baling process.

When you have a gap at every transition to every wall, it doesn’t look very good. For this reason, you have to find a way to hide the gap without ruining its purpose. I have three methods that work well yet each has their challenges. The first option is the standard application of baseboard trim. This is the obvious answer because it is what has been done in construction for many years. Most people don’t realize that the baseboard trim they see in structures is not there just for looks. It hides the gaps! This works with straw bale walls too; however, there are caveats.

First, the baseboard is attached to the framing in a conventional wall system; however, if not planned for in advance, the framing in a bale wall system is behind an inch or more of plaster. This is okay, but there is a better way. After the bales are installed and meshed and you are ready for plaster, add an additional skirt board on the face of the toe ups that will become your nailer. You can finish the plaster to this board as a straight edge and then nail directly to it when installing trim. Be sure to use a board that is shorter than your trim. For example, if you plan to use 3″ baseboard, then use a 2″ skirt nailer.

The second issue, and one that is harder to address, is the curves at doors. Because the curves are created with the stretching of mesh over the straw and are organic in form, there is no great way to attach straight, rigid wood to them. First of all, you will need to bend the material either by steaming it, back kerfing it (cutting relief cuts in the back of the trim), or by using flexible/engineered wood products. Secondly, you will need to find a way to attach the material. In some cases, cross nailing into the plaster while also using adhesive on the back of the trim is sufficient. In other cases, providing a nailer, like above, is required and that takes some pre planning of its own.

A second option is to use tile. Although completely rigid, it is smaller in length and can thus be installed even on uneven surfaces. If you install it to the scratch coat or brown coat, you can use the remaining plaster to make up irregularities. Exactly how many irregularities you have will determine which application time (scratch or brown) is a better idea. I personally prefer to attach them after the brown coat. Because of the “flexibility” of a tile job, you don;t have to provide backing and the curves at doors are not an issue.

The third option is to use J channel in your plastering to hold the plaster up off of the ground, thereby leaving a gap for the flooring to slide under. This can be challenging during floor installation as you need to leave enough space to insert your floor tool (that tool which pulls the last piece of flooring tight into the previous pieces). When complete, it looks really sharp! It basically leaves you with a shadow line at the floor to wall transition which is a great look in my opinion. Similar challenges exists in terms of attaching the J channel to the framing, especially at the door curves. As before, it is all doable and I believe the end result is well worth it. I’m a fan of clean lines and simple design. This is it for me when it comes to transitioning a wood floor to a plaster wall.

Have another way that you have had success with? Please leave us a comment below so we all can learn!

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17 Responses

  1. What about using a two foot kneewall to run electrical and transition floor to wall? Build with standard 2x construction but make it wide enough to support the strawbale above. Once electrical is run fill with blown cellulose, close it up and build the rest of the wall with strawbale and plaster. This is the idea I’m working on for my home, so I’d LOVE feedback!

  2. Andrew- I like #3 as well; is it explained in any of our “howto” videos? I haven’t had a chance to review all of them yet… Also- any thoughts on differences in long term durability of the floors and walls? For instance: if you must replace or refinish the floors, is there any difference depending on which of these methods you use in construction?

  3. Andrew, I have been thinking about the very question of what to use as a baseboard with wooden floors, and had only come up with the concept of pouring a plaster molding (so it conforms to the curves). I am unfamiliar with J channel, but it looks very nice in the picture. It will probably save oodles of time and material, as well.
    The only other idea I had for a wood floor was to slice logs and timbers into cross sections, and use them as you would tile over a concrete floor. In my 2×2 sample I made, the end grain seems to transmit heat well (nice for radiant flooring), and it doesn’t seem to expand and contract all that much, but it is a small sample.
    I’d send you a picture if I could figure out how to get film to magically be a picture on my Mac! Technology is not my strong point.

  4. On our straw bale house with wood floors we bevel cut the ends where they meet the wall. There’s still a small expansion gap at the surface but more room as you move toward the subfloor. This has worked well and looks pretty decent. But getting them just right involves scribing every board because of contours in the wall.

    Something that sits above and covers the gap would be neater but this worked for us.

    J-channel sounds like a good solution. Wish I’d thought of that.

  5. A friend of mine told me he used thick rope made of natural fibres as a baseboard once or twice. In a straw bale house it would still require skirt board or at least pieces of it here and there, but it would bend nicely in the curves. Additionally, replacing it is rather easy.

  6. Hi Bill. I have done this before and it works well. The biggest challenge is transitioning from the framed section to the bales at the doors since teh curve of teh straw is hard to reproduce with framed materials. It can be done though.

  7. Hi TK. The picture does not actually show the J channel, but it is indeed a clean finish and my favorite approach. The poured plaster idea could work, but would be fairly permanent and hard to do any repair work on the floors. Not clear about your other idea and how that would work. Let me know if you figure out a way to show me what you mean…

  8. Hi Andrew,
    Great topic to help with the finishing of our plans.

    What’s a rule of thumb for spacing mentioned in the the J channel solution? I’d hate to have a large gap but would also be disappointed to find I hadn’t left enough room for a floor tool. I’ve installed engineered flooring before but have always had trim removed. It always seemed like it was good to have open space over the floor edge to manipulate it in place.

    I’ve never installed tile before. At the brown coat, for example, you would have your floor down, adhere the tile with some glue and then finish with the last coat and tarps over flooring?

  9. We are using medium size rope. It works really well and we attach it to the sub floor in the gap with very long finish nails. It is big enough to bridge the gap and curve around our walls.I put a clear flexible finish on the rope before I put it down to aid in keeping it clean. We are even thinking about using it as a crown finish on the straw walls and getting a quarter round the same size to do the cross walls.
    So far so good.
    It was our floor guy who suggested it as he uses it in Log cabins.
    I like the tile idea as well. but that seems a bit more permanent and I would think you would want to get the third coat on before you put the floors in, well I would because I am a sloppy plasterer. Thanks for the information Andrew, keep up the good work..

  10. That’s something I have not done before. Thanks for the idea! Another person wrote to me personally about what they did. They scribed the floors (both wood and tile) to match the curve of the wall. It looks great, but takes a commitment to detail work for sure.

  11. Hi Greg. For the J channel, it is up to you in terms of how much shadow line you want. I prefer about 1/4″ above the thickness of the floor, personally. For tile, you can add them whenever you want and plaster to them. You can even add them after the plaster is complete. If you add them prior to the plaster completion, you have to protect them from plaster splash (which is relatively easy to do with tape and plastic). If you add the tile after the brown coat, be sure to rough up the brown coat behind where the tiles will lay so that the mastic can adhere well to the wall. A wire brush works well for this when the plaster is mostly dry but still influenced by the brush. Hope you guys are well!

  12. Hello My name is Kota I’m a flooring contractor specializing in handscraped hardwood and wet tile applications as well as do general flooring work when times are tough and one simple method I use on a daily basis with both are “movement joints” with large commercial tile applications it’s a requirement to use a silicon based caulk (normally blended with grout at manufacturer) across an entire length of home incase of earthquake and other “acts of God” that make a house move, in the last 6 years I’ve been doing the same thing for all edges of hardwood leaving a 1/4 to 3/4 inch gap depending upon the location and other materials going into the home base trim if no trim is used I normally take a Dremel Multimax style tool and trim the edges to matches the curve of the wall in turn it burns the edge of the wood and I use either a matching caulk for manufactured wood gaps or black silicon I’ve heard a few that use wood putty but it requires more maintenance
    If you need any tips advice feel free to contact me at 918 568 5025

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