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Open source metal lath making machine
  • I'd like to try and make a convincing argument here as to what this seemingly obscure material is, why its important, and why its production should rank in the 'top 50' machines needed to create civilization.

    So what is metal lath? It is a piece of sheet metal with perforations slit in it, then drawn so that it forms a type of mesh. Many have seen expanded metal or X metal sheets, for example heavy duty versions in walkways in factories, or inside security windows. The type of lath we're interested in is sometimes called "blood lath". It is designed to be a surface for plaster to adhere to when installing plaster on building surfaces. By far the most common lath you find in building supplies stores or hardware stores is 2.5 lb lath, which is 2.5 lbs/sq yd. Here are some pictures of lath:

    That last picture shows you what it looks like when you buy it. It comes in 96 inch x 27 inch pieces (2 sq yds). It costs about $7 per sheet at Lowes or Home Depot, and is generally galvanized.

    This company here is the largest producer of lath I believe:

    Why is this lath so important? Well, when you embed it in a few millimeters of a rich mortar, something magical happens. The the flimsy lath and the brittle mortar together transform into a material that is hard like concrete yet flexible like steel. It doesn't crack, it doesn't rot or decay, its impervious to temperature, its waterproof, and it can be used in high-performance structural applications. Think of it this way: its very similar to fiberglass and resin. You use just enough mortar to cover the steel, and you end up with something super strong after only a few layers.

    Lets look at some of the applications of this supermaterial, also known as laminated ferrocement (LFC):

    - It can be used to construct roofs that last a lifetime. Impervious to water, sun, and wind.
    - It can be used to construct water and sewage pipes.
    - It can be used to construct ship hulls. A 100' ship only needs 5/8" of this stuff for the hull. The there is a report on the Ferrocement Educational Network about Navy engineers testing this material and approving it for boat hull construction.
    - It can be used as a structural member. A beam can be made by forming a tube shape. Applications include everything from roof supports to bridge trusses.
    - It can be used to construct raised beds and planters that will never rot.
    - It is highly efficient for construction of large water tanks, fuel tanks, cisterns, stills, silos, and other such structures.
    - Strong thin-shell dome buildings can be constructed.

    Depending on how many layers of LFC you use, the above items that you build aren't just lifetime construction, they will span generations. We're talking building something that will stand perhaps 500 years. I think others have also recognized the value of ferrocement and made a really nice wiki page on the topic:

    I see that we're trying to make a Global *Village Construction* Set, and yet for actually constructing buildings, I'm only seeing a compressed earth brick machine and a saw mill (maybe the cement mixer as well). Almost all the tools seem to be focused on making machines to either work land or produce other machines and industrial products. However, without a roof over your head, there will be no plasma cutters or automated self-replication. I'm not seeing where the roof comes from when I click on the main page and scroll down to the GVCS technology map.

    The above bullet points clearly fill an indispensable role in any agricultural setting, and a role currently not currently filled by the GVCS in many cases.

    So now, in my mind, the question becomes, is building a metal lath making machine feasible, and is it worth it? Why does a 5 lb piece of steel cost $7 at Lowes? Why isn't this a more widely used construction method? Lets try to answer these questions.

    The high cost seems to be a result of the relatively low volumes. Very few people buy it at home improvement stores. The reason for this is cost, for one thing. Its much easier for a home owner to get a cheap, precise, visually pleasing piece of plastic or wood than to get his hands dirty mixing mortar, having to deal with irregular surfaces, and producing a more expensive and less visually appealing result. Likewise, a contractor isn't going to go through the effort of manually forming, nailing/stapling, and mortaring, which takes time and labor, to make something that truly lasts a long time, when its in his interest to just get the job done as fast and cheaply as possible.

    In addition, laminated ferrocement was a discovery that was patented for building ships. This isn't a process that's been widely circulated or known about. This material hasn't been as available or widely known in other countries either.

    I'm told that one can buy a pallet with 500 pieces of 2.5 lb metal lath for $1.95/sheet. This is much lower than $7. And the stuff doesn't need to be galvanized for our purposes either, which saves additional cost. The fact that people, even myself, find it economical to use the stuff at $7/sheet, should give a clue as to is inherent value. Open sourcing a machine that is designed to make lath specifically for structural purposes (2.5 lb lath in 27 x 96" sheets isn't the most ideal), would open doors to new possibilities in construction.

    As to the feasibility of making such a machine, I cannot answer that. I encourage everyone to buy a sheet at a hardware store and think about what it would take to make it. Its with the plaster and stucco, by the roofing and mortar/cement area.

    Laminated ferrocement, coupled with compressed earth bricks, would be the foundation for a superior shelter construction model. It is also very versatile for many other applications.
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  • It is some useful stuff, I have used it in masonry work, it is used to hold brick/stone onto a wall. You screw the lath to the wall and cover it with wet mortar as you lay the brick/stone. It is very useful stuff and would probably work well with CEB construction. Flat pieces of this lath set in between layers of compressed earth blocks in addition to a bit of mortar would make a much stronger wall. Furthermore if you left the lath sticking out on the side you could bend it down along the surface of the wall. This would provide an excellent surface to apply adobe/stucco/mortar to as it would be varied in shape, it would be load bearing, and the interior lath material would anchor the blocks and improve earthquake resistance and overall durability of the structure.

    I would assume it could be made on the metal rolling machine by making two interlocking drums that you roll a flat sheet of metal between. That could cut it and expand it to that shape at the same time and would produce it as fast as the rollers ran it through (since it is only ~1/8 thick it would roll very fast on even a moderately powerful steel roller). This would mean it is not a whole separate machine that needs to be designed and built but rather just a die for the appropriate metalworking tool (maybe not even the rolling press, I am not a metalworking expert either but this should be possible).
  • @ jason - I'm thinking combine these techniques with stabilized Earth bricks while building proper Earthships would be an unbeatable combination. Mike Reynolds has been building Earthships for 40 years now. Have a look:

    Try to imagine a home that needs no utility hook up. No water, no sewer, no power and it grows some food in the greenhouse portion using gray water as food for the plants. Also no furnace is needed. It heats itself too.

    Check it out.

    The Dawg
  • Here are some great videos of lath making machines that Ringo posted over at the ferrocement education network.

  • @jason - I suggest that we capture this in the wiki, if you haven't done so already.


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