When building, the question of what type of mesh to use in a straw bale build is a big one. I show the use of 14 gauge welded wire mesh in my videos, 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.
35 Responses
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?
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.
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
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.
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.
You mention HardyFrames…are they a viable option for the owner/builder?
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.
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
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.
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?
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?
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
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.
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.
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!
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.
Awesome. Thanks Susan.
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.
If one is planning on plastering the outside of his bales with lime, can you also use a lime plaster as a slip to stick the bales together as you stack them?
I will take my answer off the air, thank you.
John,
You can use the lime to mortar the bales together; however, I do not believe it is necessary to do so. It will be expensive, and if the walls are constructed properly, they will be plenty tight without the use of any slip whatsoever.
So… these questions may sound somewhat elementary, but I assure you that I have done my share of SB reading, which seems create as many questions as answers.
In my case I am building a 2 story house, the top story is typical 2×6 framing and the bottom floor SB. The first floor I built a wooden deck atop of piers added post and then wrapped the post with treated 2×12, installed LVL beams and then built my second floor deck, then walls, and roof. Now I am about to tackle the straw bales. I am going to use a Lime Plaster on the outside and Clay on the inside.
My questions are:
A) With a wooden deck is there anything I should do to attach the bottom row of bales to the deck or simply stack them?
B) I have seen a lot of back and forth about pinning bales, rebar seems passe, and I have read were some don’t even pin at all except for in trouble areas and then they use wooden surveyor stakes.
C) I know that B) didn’t end as a question but at the end of this one you can see how it relates. Lathe: I have read through all the to lathe or not to lathe entries here and in other places, and understand that lime has no problem adhering to straw with out a lathe. SO, If the bales don’t attach to the deck, you don’t pin them, and you don’t use a lathe, and you don’t stick them together with a slip do you really just stack them up and plaster??
D) And I know this question should probably be posted in the plaster section. I have access to Hydraulic and Quick lime both at a cost of 100 dollars a ton. Affordable. I like plastering with the quick lime better, however due to it’s reactive nature while mixing I will probably stay with the hydraulic lime. Has anyone used an electric mortar mixer to mix up quick lime? Was it safe?
E) And last- I am looking for a resources for color additives for my final lime washes there are probably some on this site.
Thank you Andrew and all this is a fantastic Straw Bale site.
Good questions John. I do not have answers for all of them, but I will do my best and hope that others may be able to answer for you. If you look at the recent blog post about plastering (https://strawbale.com/an-overview-of-clay-lime-and-cement-based-plasters) you will see a comment from a guy named Ken. He seems very educated in lime work and may be able to help you further on some of your lime related questions. You can also contact the folks at http://www.limes.us with questions as well. They are very helpful too. Okay, here we go:
A)The use of 20d nails 4″ on center, staggered on each side of the top of the toes ups (both toe ups) acts as a grabber for the bales. This is all I do to attach my bales to the floor. Be sure to use a toe up though for several reasons. 1) plaster mesh attachment (more on this later) and 2) protection from water leak damage to bales.
B)I never use wooden survey stakes. If I do attach a bale with some time of pinning system, it is a squeeze block. This is a 2×4 nailed to the framing and then beaten down tight on top of the bale course. It holds the bales really tightly to the frame and works far better than any pinning.
C)I always use some type of mesh when baling. Consider that it is needed to shape around windows and doors and is a good idea for reinforcement at corners. Once you have done all of this, you will notice there is very little area left without mesh so it is worth using it everywhere (thus the tow ups as noted earlier). It is good insurance for the plaster bond and helps hold stuffing and other aspects of the bales in place. The mesh is perfect for holding the bales to the frame as well, especially when sewn to together.
D) I have not done this so I cannot comment.
E) You can get good colors from http://www.limes.us. Let them know I sent you and they will take good care of you. 😉
Thanks for the kind words John. I hope you continue to learn from the site and gather motivation to build the house of your dreams!
Hi Andrew great stuff. I really enjoy reading and watching your vids.
I have a little project on the go.
My questions first.
Is full mesh needed when using cement based stucco, sans code?
I’m not really understanding in what direction, when you are talking shear forces. Is this the main concern or is it the actual adhesion to the bails the problem with working with a cement base?
I will try to explain my build to give you a little more insight.
I am constructing a 30×40 shop in Alberta Canada, no code since it is a shop.
The tin roof is supported by 2 7/8 drill stem on 10′ centers, 4’roof overhang on all sides.
The walls are 17′ high pined to a 22″ cement foundation and pinned every 3 bails. And pins attached to the roof header at the top. Yes 17 feet or 14 rows of bails.
The 2 7/8 pipe supports are anchored in the center of the foundation, bail ends notched at pipe.
1/2 way up the wall I have run a header horizontally between the 2 7/8suports in order to prevent the bails from moving in and out.
I have begun spraying a mixture of 1 #10 portland x1 s lime x5 #8 masonry sand on the bails. I built a peristaltic pump to apply the stucco with the help of an air compressor. Bails are trimmed and holes filled. The stucco seems to be imbedded in the bails really well. First cote is ¼ to ½ “thick, troweled after spraying on and scrached.
I have read that a wire mesh should be used with cement based stucco. I have attached 2×2″ welded mesh to the corners and to window openings, but not to the rest of the bails.
Sorry for the long wind.
Stephen
Hi Stephen. Sounds like an interesting and BIG project. The mesh is used to increase the strength of the plaster when it comes to cement. Cement is very brittle and so can fracture and crack easily without extra support. The bales themselves provide excellent “tooth” for the plaster, yet mesh embedded into the plaster will help it stay strong and will limit the amount of cracks the plaster will see.
The shear direction I refer to is best identified as the direction the house would move if someone were to push against a wall in line with that wall. Hope that helps.
Thanks for the reply Andrew. I have decided to use the mesh
on all of the straw. It should take me all winter to get it sewn on.
Stephen
1.Can you extend this explanation (do you have any pictures ?)How to build this squeeze block ?
“B)I never use wooden survey stakes. If I do attach a bale with some time of pinning system, it is a squeeze block. This is a 2×4 nailed to the framing and then beaten down tight on top of the bale course. It holds the bales really tightly to the frame and works far better than any pinning.”
2.I choose to slip bath with earth plaster the bales on both sides, my question is:the bales need to be trimmed (individually) before this action ? The bales aren’t quite straight.
3.I’ll try to attach the mesh after the bath slip operation. Is it ok ?
1. The 2×4 blocks are nailed down between the framing members of the wall on top of the bales. They only pinch the outside 4″ (between the framing).
2. I don’t like slip baths for just that reason. You’ll have to use a weed whacker after they are installed as cutting them in advance will not help line up the wall in the end.
3. The mesh will have to be attached after the bales are up and straightened to serve its purpose.
Does anyone know what materials to use for an eco friendly mesh ?
Guna
I have heard of people using jute and hemp netting. It does not have the shear strength properties of the mesh, but it is a strong mesh for plaster reinforcement. I look at the mesh as a multi-system material. It provides shear strength to the building, reinforces the plaster, creates the shapes for the curves, replaces the internal or external pinning of the bales (rebar or bamboo), adds strength to allow for hanging cabinets and other heavy items, and so much more. When you consider it in this way, it is a good material to use as it covers so many aspects of the construction with only one material installation.
You said that wire mesh is expensive. If I had known this I might have been able to make a better plan before I decided that I needed it. I’ll need to do some research about maintenance for wire mesh so that I know it is being properly taken care of.
Hi John. It is not so expensive that it’s not worth using. It provides a HUGE benefit to the wall assembly and is worth every dollar of installation cost in my opinion. In fact, probably more.
What is the best way to estimate mesh and lathe coverage?
Simply use the square footage of the wall to be covered and then divide by the square footage of the material. You need to overlap mesh by a minimum of 6″ and lath by a minimum of 3″ so you can add about 10% for that to the total. You also need to account for waste from off cuts, so another 10% will keep you safe there. With special order stuff like the mesh, it’s worth having too much as too little leaves you in a bind AND has steep deliver costs associated with it if you need to order ore last minute.
Can I use burlap for the meshing over the strawbales?
Hi Rob. Burlap can be used; however, it does not provide anywhere near the same value as using mesh. It doesn’t have a lot of structural strength so you can’t use it to install electrical fixtures, cabinets, and other items the way you can mesh. It also does not provide any shear strength to the wall. It is basically a substrate to add loose stuffing behind while adding a little bit of plaster reinforcement, but that’s all. Cheers.