Firmly Attach Mesh to Protect Your Plaster – StrawBale.com

Written by Andrew Morrison

Welded Wire MeshWhen working with straw bale buildings, some people wonder whether mesh is necessary or not. I personally think it offers so many advantages that I don’t consider not using it anymore. So with that bias in front of me, I want to share a really important detail about mesh application.

You need to firmly attach mesh to protect your plaster. If it is left loose, then the plaster will hang on the mesh and may separate from the wall as a result causing cracking and potential failure. The best scenario is for the plaster to hang on the bales and for the mesh to be embedded in the plaster. This provides the best strength for the plaster.

welded wire mesh over straw bale

Be sure to staple your mesh well at all wood intersections and tie any loose areas through to the other side of the building. Landscape pins are not a great solution. They work well in certain areas, like attaching blood lath around niche, but for holding loose mesh, nothing is better than staples to wood and sewing mid-bale areas.

Take the time to firmly attach mesh to protect your plaster. Imagine yourself as plaster hanging on your mesh as you inspect the entire house once you think you are ready to get mud on the walls. Pull on sections of mesh to see how tight they are. Check the areas at the top of the wall, around windows and doors, random field areas. That final inspection may be the difference between a beautiful home and a cracked plaster failure.

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21 Responses

  1. Ever use 5.5 oz hemp/jute burlap mesh? Try it, you’ll like it! Makes your plasters flexible and crack-proof.
    Allows you to take saws and hammers for “oops, I forgot” situations (electrical, niches, etc.) without comprimising the whole wall of plaster, or a bunch of saw blades.

  2. Hi Tim. Funny you would say this. I just suggested this material to a guy at the plastering workshop as a potentially awesome idea, especially since he is trying to use as many natural materials as possible. Thanks for the feedback on the material.

  3. 1.How about spraying the first layer and then attaching the mesh ?
    2.The jute burlap mesh should be used on the framing lumber + roofing felt not for whole wall right ?
    3.Blood lath above windows and doors still the no.1 ? Or can be managed everything with the welded wire mesh ?

    Thank you,
    Adrian

  4. 1. I would not attach the mesh after the scratch coat. It needs to be attached firmly to the wood and then sewn through from side to side. Also, I want the mesh to be embedded in the plaster, not acting as a separation layer between coats.

    2. I would use the jute over the whole wall. It serves many purposes from shaping to holding cabinets in place when used properly.

    3. I still want blood lath over the windows to hold the plaster. The welded wire does not provide enough backing for the plaster. The jute might, but I still prefer to use the lath for the best results and easiest plastering.

  5. Would burlap, such as gardeners use, work to cover the wood surfaces (such as the posts and beams) instead of using roofing felt?

  6. Burlap could work although roofing felt has been an industry standard for a long time (stucco construction not necessarily on SB house). Burlap would likely be a more natural choice, but would take more labor to install.

  7. What about staples dimensions and where could this stapler be found ? It is like a big paper stapler ?

  8. Hi,

    I have read in a book or two that there is a plastic mesh for plaster, instead of using the metal. Do you have any resources or experience with a plastic? I am planning to use a lime-based plaster and am re-orienting myself with information. Thanks.

  9. So I’m wondering if you staple the mesh to the wood at the top and bottom (bottom wood curb), wouldn’t stapling it to the bottom (through the 18″ felt and the metal flashing) compromise that weatherproofing? And if you didn’t staple it there, but just stapled at the top and down the wood posts TO the 18″ felt along the bottom, wouldn’t the felt bow out and make the mesh also unstable? Can you elaborate where the staples go in this system? Thanks.

  10. Hi Lynn. The mesh should definitely be attached to the bottom toe ups and the posts and header/beam. The more nailing surface you use the tighter the connection will be. In terms of the weatherproofing, no, it is not compromised. The plaster itself moves most of the water away from the structure. If you are concerned, you could use a self adhesive flashing wherever that concern exists for you as it will self heal when penetrated.

  11. Hi Andrew – Bought your DVD years ago now, but finally we’re at a stage where I have a question. Our first straw bale structure is ‘not’ relying on the plaster for shear, and we’re going to be using earthen plaster (mixing up clay soil for uniformity we hope). My question is regarding jute mesh with 1/2″ x 3/4″ squares – 12 feet wide roll. Question: Do you always put mesh up ‘before’ plastering. For some reason I see logic in putting on the scratch coat, then laying in the mesh, like the way you do with mesh in drywall seams. Obviously it would have to be cut and overlapped, but is that crazy?

  12. Hi Susan. You’re best to add the mesh before you plaster. That way you can tie it through from one side to the other and then add the strength of the mesh to the plaster. If you wait to install it until after the scratch coat, you won’t have enough plaster in the brown to fully cover the mesh. Standard practice definitely applies here, install the mesh first and then start plastering. Have fun!

  13. Do you have a link/source for this jute mesh? I can’t get the 2×2 wire mesh local except for something like $2/lin ft. I can get 2×4 fencing or chicken wire. My plaster does not require the mesh to support the shear, by P&B building will take care of that.

    I had a look at your resource center, but not much seems to be getting listed on my browser?
    Thanks
    Ryan

  14. I bought my rolls of 5.5 oz Jute Mesh from Dayton Bag & Burlap. Any heavier mesh prevents the plaster from penetrating the weave. The erosion control mesh is even more open, but probably more frayed and unpredictable for trowelling into the scratch coat. I haven’t tried it–what’s your experience?
    What I do:
    Thin scratch coat, stick the mesh up by hand, then quickly trowel it in with another thin scratch to cover/embed it. Soaking/spraying the mesh with (lime) water makes sense, too.

  15. Hi Tim. I prefer to have mesh attached to the frame, not laid into the plaster. In fact, I am a fan of using welded wire mesh over jute netting. I know that the jute is more natural a material and I like that aspect of it; however, I like the strength that the welded wire mesh provides for the structure. In fact, and in light of the recent earthquakes, I believe that the extra strength provided by the mesh is well worth the impact of using it.

    That said, if you do choose to use jute (again, I am not against that and will in fact be installing it in my Ontario workshop this year) I would prefer to see you staple it with pneumatic staples to the frame and stretch it as tight as you can. Be sure to push the plaster deep into the bales so that the jute ends up embedded in the plaster.

  16. My understanding is that “standard practice” is to fully encase reinforcement within the plaster, both for corrosion protection as well as to fully realize the reinforcing potential of the combination of materials by having the sheer strength of the mesh encased in the compressively strong plaster. This is why metal lath has raised nubs stamped into it, to provide necessary furring off the sub-base to be plastered. That’s where cinching it up tight to the face of the bales seems a departure from standard practice.

    In regards to sewing through the wall, what kind of pattern would you suggest in terms of the spacing of the through-ties? Any specific twine product or specs recommended?

    Any leads on West coast suppliers of 2×2 welded wire mesh?

    If the structure’s shear system is entirely independent of the bales and plaster, would a non-structural mesh be adequate? I’m not sure I understand the way you are using this heavy mesh to assist in anchoring cabinets, electrical etc.?

    Finally, there’s a revolutionary new reinforcing material made from Basalt, the most abundant rock on Earth. This will never rust, has the same thermal co-efficient of expansion as masonry materials, is non-conductive and is 9x stronger than steel by weight. Hopefully we’ll be seeing more of this on the scene.

  17. For sure you want the mesh encased in the plaster. Pulling the mesh tight to the bales does not impede this as the plaster pushes into the bales a bit as well. If the mesh is loose, then it causes weak plaster.

    I sew with standard poly baling twine 2′ on center or where ever else it needs it to get the mesh tight to the bales.

    I buy my mesh at Flynn and Enslow in San Francisco.

    If you are not using the mesh for shear, you can go to a 16 gauge welded wire mesh. I would never use chicken wire or stucco wire as it is too flexible and does not allow you to shape walls well. The electrical and cabinetry is anchored behind the mesh. It’s hard to describe, but I can show you in my DVDs or at a workshop. I may even have some free explanations on StrawBale.com. Just search the blog for hanging cabinets or installing electrical. I used to use spikes, now I use the mesh with plywood plates.

    That basalt mesh sounds cool. i have not heard of it before.

  18. I purchased 1″, 1/2″ and 1/8″ basalt meshes from http://www.smarter-building-systems.com and really like the quality of the product. The epoxy coating makes the mesh about the perfect balance of rigid and flexible. Radiuses are second nature, the downside is the material is very springy and does not like to hold sharp corners. This applies from the mesh to the rebar. As I recall the product cost was a bit more than half that of expanded metal mesh from the local building yard; maybe from 40 to 50 cents a s.f. depending on mesh size. The chopped fibers were a dollar and change a pound compared with polyester fibers at ten bucks a pound at the redi-mix plant. The rebar was significantly more expensive than its steel counterpart, and only available in large spools, not that it applies specifically to bale building. Relative to steel this product is far lighter to ship.

    Basalt reinforcing has low embodied energy, made from a single source material; ubiquitous basalt rock, formed from fast-cooling lava, which just happens to be what all the seabeds are made of. Basalt is ground up and melted down at a fairly low temperature of 2,550F, then extruded into long continuous filaments that are formed into meshes, felts, twines, roving, mats, fabrics and bundled into rebars. There’s a quick though slightly thin Wikipedia on basalt fiber here http://en.wikipedia.org/wiki/Basalt_fiber

    By just reading it I learned this technology was only just declassified in 1995! You know how they say being excommunicated by the Church is the best sign you’re on the trail to the truth? I think same goes for being classified; if it weren’t a revolutionary material, there’d have been no need to cloister it.

    One huge advantage is that the material will not rust or rot, so plaster and concrete can be applied only to the thickness required to achieve the desired structural performance. Imagine how many millions of yards of concrete are currently used all for the sake of providing protective cover to prevent rusting of the steel reinforcement. Worst of all is that concrete & lime slowly lose their alkalinity over time, eventually causing the demise of the reinforcement anyway.

    Basalt reinforcement can be used right below the surface with no concern of degradation. Because it is stone itself, it expands and contracts at the same rate as the plaster it is reinforcing, relieving expansion/contraction stresses.

    From a long range perspective, life expectancy should top the list. This seems to be all the more applicable to plastering over bales. When steel reinforcement corrodes, that rust expands to occupy 2-4x the space as the steel did, causing delamination and spalling off the plaster face. The necessary replacement of the plasters seems a very unattractive prospect.

    Unfortunately, the mesh is not currently made in a 2×2″ opening that I know of. Hopefully the 1″ opening will still allow enough exposure to the bales for properly keying the plaster into the straw fibers.

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