Tuesday, January 29th, 2008 | Popularity: 79%
One option is to not use mesh at all for the majority of the structure. This is only applicable when the structure is plastered with an earthen or lime plaster as cement based plaster require a structural mesh by code.
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When building a straw bale house, the question of what type of mesh, if any, should be used is a big one. I show the use of 14 gauge welded wire mesh in my DVDs, and that is a great option; however, it also has its downsides like any other application. For one, it is expensive. Secondly, it is a bit harsh on the environment to use so much steel. So, what other options are there?
One option is to not use mesh at all for the majority of the structure. This is only applicable when the structure is plastered with an earthen or lime plaster as cement based plaster require a structural mesh by code.
Another option is to use plastic mesh like Tenax. It cuts with a utility knife and is lightweight which make it easy to work with. It stretches a bit, like the old days of chicken wire, so it can be difficult to maintain a desired shape.
Jute netting is an environmental option that will work well with earthen and lime plasters. It is a bit harder to find in some markets, but is easy to work with and has a low impact on the environment. It is difficult to successfully shape corners with jute because, like chicken wire or plastic mesh, it does not hold a shape well.
Stucco netting or even chicken wire can be used; however, I find them to be not worth the hassle. They are very flexible and sharp and are made of steel. If you use the steel, then I suggest moving up to the welded wire mesh as it is far superior to the stucco netting or chicken wire.
In any situation: no mesh, jute, stucco netting, chicken wire, I recommend using a stiff wire on the corners. The welded wire mesh I use is a great option because it holds a shape very easily. This allows you to create smooth corners without the bumps and holes that you might otherwise have with the other materials. What mesh you choose depends on the design and finish you are going for as well as your structural design. Keep in mind that the welded wire mesh I use in my DVDs can be used as the lateral shear design for the home, eliminating the need for shear bracing. Although I no longer use that method as my number one option, it is still viable and a good choice for the owner builder. I now use HardyFrames or other structural shear panels in my homes for shear walls. They are expensive as far as materials go, but they cut back on labor costs which, as a contractor, are more of a priority than material costs.
Popularity: 79%
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Andrew Morison is a licensed contractor specializing in straw bale and green construction. He has shown thousands of people how to build their own straw bale projects through his comprehensive series of instructional straw bale, concrete foundation, and plastering DVDs. You can check these out at http://www.LearnStrawBale.com.
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January 30th, 2008 at 4:33 pm
Andrew Ive read alot of straw bale books that say using a mesh behind earthen plasters is not a good idea. what are yor thoughts. Is it as strong when not reinforced? What other method would you recomend for holding your bales together if you didnt use a mesh?
January 30th, 2008 at 5:06 pm
The straw is definitely strong enough to hold the plaster. Be sure that your walls are tight and compressed well and then use some type of lathing in between courses to attach the bales to the frame. If load bearing then use strapping to hold the box beam to the foundation. The compression will hold the bales tight in place. Personally, I prefer to use some type of mesh to hold things in place. I like the welded wire mesh best even though it is expensive and fairly difficult to work with. I think it gives the best results in the end.
January 30th, 2008 at 5:34 pm
Thank you I agree with you on the welded wire mesh. I t makes sense to you use it for the strength and the end look you get with it. Also being able to sheer your structure with it is a huge bonus. I just wanted to be sure there was not any negative aspects of the mesh with the earthen plasters. Where the best place to find the mesh? Fencing/ farm stores? Thank you
January 30th, 2008 at 7:37 pm
On the West coast, you can try Flynn and Enslow in San Fransisco. I am not sure where to get it outside of the West coast because that’s where I live. Some farm supply stores will have it but most carry either woven mesh (no good) or 1″ x 2″ welded mesh (okay but not tested for shear). An internet search might be a good start as well.
January 31st, 2008 at 10:33 pm
Hello, I have a question to welded wire mesh and other metalwork that are used in straw bale walls. Could not they caused water condensing and then rot? I have read that some people use hazel limbs for pinning the bales (if pinning is necessary) to minimize a cause of rot.
February 20th, 2008 at 6:57 pm
You mention HardyFrames…are they a viable option for the owner/builder?
February 20th, 2008 at 8:44 pm
Todd. Hardy Frames are very easy to work with and can be used by owner builders for sure. They are not cheap though and so you need to balance cost with ease of construction.
February 26th, 2008 at 9:02 am
From my experiment with bale building, do not use any metal mesh it causes a chemical reation and promotes moisture. The best is to create a slip bath of earth plaster/ or cake batter consistency clay.Then by pushing the bales into the bath, on both in and out faces, the slip pushes into the bales to create a coating that will not need meshing. By doing this you also create less trimming and a great bond for the scratch coat
February 26th, 2008 at 9:24 am
Susan,
I like the sound of your system; however, keep in mind that if people use a cement based plaster, they are required to use mesh. You can only get away with no mesh with natural plasters because their flexibility works well with the bales. Also, if people use the mesh as part of the engineering for the structure then certain requirements are in place. Like I say, I support the system you use as long as the above criteria are addressed.
March 8th, 2008 at 8:23 pm
Andrew…I bumped into a friend the other day that had just finished an 1800 sq. ft. strawbale house. She said the biggest thing she would have changed was instead of post and beam infill, she would have left the frame exposed and done a bail wrap. While I’ve looked at this before, what I was wondering what provides the “shear” on a bale wrap house? Would the post and beam framework have to be more like a timberframe with diagnonal braces so that the frame itself provided shear?
March 8th, 2008 at 8:26 pm
After reading my post,let me clarify. In a bale wrap house, there wouldn’t be any posts in the wall for the mesh to be stapled to, therefore the only attachment points would be the floor and the roof trusses. Is that enough, or would metal strapping work better?
March 10th, 2008 at 2:00 pm
Hi Todd. In order to build a house with a wrap like you speak of, you need to consider several things. The first is, like you mention, how to shear it. In the easiest case, one would use the frame itself to shear. That would require the use of knee braces like the traditional timber frame look (diagonal braces on either side of the post to the beam).
The second is how to attach the bales to the frame. Attaching at the top and bottom only is not enough. You would need to use plaster lath bent in half (take a 16″ x 8″ piece and bend it in half to two 8″ x 8″ sections) and staple it to the frame and pin it to the top of the bales every post and every course to keep the bales firmly attached to the frame.
A third consideration is that the roof trusses will have to be designed to accommodate the extra width of the bales outside the bearing point of the framing. What this means is the trusses will have to extend out beyond the structural frame in order to protect the bales. This is possible; however, consider that a 2′ minimum overhang is desired and when adding the width of the bales, you will have to have a set of trusses engineered to cantilever 3.5 feet from the bearing point at a minimum. That is a lot.
Windows and doors are another consideration in this design system. They will be installed in the frame, typically; however, in this design, you will have to build bucks for them to extend them to the exterior of the wall. Otherwise, you will have huge exterior window sills (bad idea for water leakage).
These are just a few things to consider in the design method your friend suggests. I don’t want to turn you off entirely of the idea as an exposed frame can be beautiful for sure. Just make sure you think it all the way through.
Andrew
March 18th, 2008 at 5:10 pm
Thanks Andrew. I’m still leaning towards post and beam with infill, I just wanted to make sure I understood my options, and the issues associated with them.
March 19th, 2008 at 5:40 am
Hello Andrew,after our conversation on Feb 26th I headed to the barn to do an experiment with a cement based plaster and did the same process with the slip bath. Pushing the bale into the bath by sitting on it, flipping it over,and did the same as the first side, wipping off the excess on both sides. I then stacked them until I had a small partition wall using this process. After they dried over night the next coat went on without any mesh and no trimming was needed. A master stone mason friend of mine came to inspect the results and was impressed.
March 19th, 2008 at 5:50 am
That is great Susan. Thanks for reporting back. How long did it take to do the slip bath? Do you think it was time efficient in the end and could you imagine yourself doing it with several hundred bales, lifting them to a height of 9 feet? Again, thanks for checking this out!
March 19th, 2008 at 6:38 am
To do the bath was really no problem, because of the fact that I already had the bath previously made. I made it with 2×12 for the 4 sides with 1 inch plywood on the bottom. I lined it with an old pool liner, doubled. The frame is about a 1.5ft longer and wider than the bales I get.I only fill the bath to the half way mark so not to overflow when the bales are pushed in. The process is a bit messy for the person doing the dipping, a pair of painters overalls work great. I dipped the sides that don’t have the twine, so that makes for easier handling and passing. I did not weigh the bales before the bath or after, but they did not seem that much heaveier for this 120lb farm GIRL to lift and handle. My wall height was only 6ft and with the scafolding that I set up the bales were easy to handle and put in place. As far as time efficient, I think YES in that department. The time spent mixing and dipping vs mesh attachment, pinning(sewing-two people needed), trimming and the cost for that whole process in dollars,personal energy and time, I think the dipping is best. I also find that the dipping gives you a great base to apply the scratch coat.
March 19th, 2008 at 11:17 am
Awesome. Thanks Susan.
April 23rd, 2008 at 2:09 pm
There is one possible problem with metal mesh in the walls of houses that has not been addressed. Electricity is everywhere, in the air in the ground everywhere. having a house covered in a network of interconected conductive material could produce an electrical field within the house. I’m not talking about electricity leaking from wiring, I’m talking about the natural passage of electrons from one atom to the next.
Static Electricity.
Steel is very good at conducting this type of exchange, try standing out in a thunderstorm with a number 2 iron. :o) The electricity for lightning doesn’t come from the clouds, it comes from the earth.
Although the mainstream science community fails to recognize the danger of electrical fields, many studies have shown adverse effects on human and animal health, due to long exposure to them.
Bees have a much shorter lifespan if the hive is near overhead powerlines. This is due to the electrical fieds generated in the wires “exciting” the bees to work harder, quickly working themselves to death.
Naturally occurring static electricity could be flowing through the wire under your stucco creating a low level electrical field. This may affect sleep, concentration etc. as has been reported in England as long ago as the 1970’s.
I’ll stick with plastic mesh.