I know that the topic of metal in straw bale wall assemblies is a contentious one, and that is precisely why I want to bring it up and talk about it with you all. I have been saying for years that the use of welded wire mesh and plaster lath is essential to a quality bale house, and that sentiment has not changed. I want to quickly share my thoughts about using metal mesh and lath, and then hear from those of you who either agree or disagree with the practice. My preference is that you only write in if you actually have experience with using (or not using) metal mesh and lath and that the conversation be held to those with something to share from the experience, not from assumptions or beliefs. Of course, that’s my want and I have learned over the years that I don’t always get what I want. 🙂
Top 5 Reasons to Use Metal Mesh and Lath
- Wall Strength. This is the most obvious of reasons for people who have built with the metal before. There is nothing that tightens up a straw bale wall quite as well as applying welded wire mesh over both wall surfaces and then tying the mesh tightly together. The out of plane (forces applied perpendicular to the wall surface) and lateral (forces applied in line with the wall surface) strengths of a bale wall system are greatly increased with the use of mesh. Further, there is no need for internal or external pinning to hold the bales in place when using mesh, so the practice not only increases strength, but also eases and speeds construction.
- Electrical Installations. The old system of vampire spikes simply doesn’t work well. By utilizing the mesh as an anchor point, small plywood plates that hold the electrical boxes are permanently attached to the wall and cannot move once installed. This is a simple and effective way of installing electrical work to any bale wall.
- Cabinet Backing. By installing horizontal 2x4s (or larger) into the bales and then attaching them to the wall by means of the mesh that overlays them, one can create a permanent backing for heavy items that will eventually be anchored to the wall. This could be cabinets, large mirrors, artwork, or anything that requires extra support.
- Shaping. Bale buildings are known for their beautiful shapes. Welded wire mesh is the best way to get the shapes you want because it does not stretch when installed. You can apply a lot of force to the mesh to get very tightly packed curves, thus creating solid backing for the plaster application.
- Stuffing. Every bale wall needs to be stuffed from time to time in between bales or other areas where the backing for the plaster isn’t quite adequate. Stuffing that is applied to the wall without anything to hold it in place, such as mesh or lath, will simply fall out of the wall once the plaster adheres to it under the weight of the plaster. Even if it doesn’t fall out, you can be sure that it is not offering any positive attachment for the plaster, so it surely is not helping the situation.
- Okay, I know I said 5 reasons, but this one is important too: Spanning Over Wood. When plaster has to span over wood elements of the structure (posts, beams, etc.), it needs a way to anchor to the wall. Asking plaster to stick to wood is a bad idea because the wood will expand and contract over time, causing cracks in the plaster. Hoping that the plaster will span across the framing members from straw bale to straw bale is risky too because plaster is not designed to handle that kind of stressful span. Instead, applying plaster lath over a waterproof membrane (roofing felt, for example) on top of the wood elements provides the strength and durability your home needs.
Okay, there are my five (plus one) main reasons for using mesh. I have others, but I said I was going to keep it short and sweet. So, what are your thoughts?