I’ve made numerous references to ferrocement in my previous articles in this series, but haven’t been too clear on what it is. The reason I couldn’t help talking about it before this article is just because ferrocement is so useful and versatile. Now we’ll see just how crucial of a tool this will be in a fascist builder’s arsenal.
The search for the perfect material
All construction materials have strengths and weaknesses. Bricks are fast and easy to lay, but expensive and relatively fragile. Cob is free and simple to make, but vulnerable to moisture and labor intensive. Concrete is tough and waterproof, but requires molds to pour into and is expensive when you use a lot of it. Wood is light and strong, but demands great precision in assembly, and is vulnerable to the elements.
The smart builder will use the materials that are the best fit for the job, and will combine materials to offset their mutual weaknesses. But there’s one material that is gaining popularity because of it’s great versatility.
What if you took the toughness of concrete, and removed the requirement of having a mold? What if you had the flexibility of steel, without the rust? What if you could use a fraction of the concrete to get the same result?
Ferrocement is very simple to explain. You use steel mesh (chicken fencing) and rods (rebar) to sculpt a shape. Then you manually apply concrete to this shape until the steel form is entirely covered. That’s it. Why is this so great?
The steel mesh will “wick” the cement, preventing it from dripping off. This is what allows us to avoid using a mold to “hold” the cement as it dries. Because the ratio of steel to cement is much higher than in conventional reinforced concrete, the strength of the material is very close to pure steel, yet the concrete, if there are no failures or air pockets, will protect the steel against rust. And because the strength of the material is so great, very little of it is necessary compared with poured concrete. A small water tank could have walls less than an inch thick and still withstand the water pressure.
Because of all these properties, you could use ferrocement for practically anything. It’s water proof, fireproof, can withstand enormous loads, can be made to fit any shape (I knew a guy who made actual sculptures using this techniques) and is relatively simple and cheap to use. But probably the most popular use right now is making cheap and durable water tanks.
If you live off grid and independently from the System, there’s many reasons why you’ll want to store water. Of course, if you don’t have a well or access to a stream, then you’ll need to accumulate rain water. If you’re growing your own food, storing water is necessary to water your crops in dryer times. Emergency supplies of water can be a lifesaver in the case of a fire, or if your normal source of water fails you for some reason.
You can of course buy metal or plastic tanks, although they’re expensive. And in reality, their performance is far inferior to a ferrocement tank. Steel tanks are very strong, but vulnerable to corrosion – they have a relatively short life-span. Plastic tanks can leech toxins into the water and will get degraded if exposed to UV radiation (sunlight), and thus are usually buried underground. Yet if a lightweight plastic underground water tank sits empty for too long, the air pressure will tend to push it out of the ground (in the same way an empty water bottle will float above the water.)
Art Ludwig’s Water storage has detailed instructions on building ferrocement water tanks of all sizes. I strongly recommend consulting that book before you set about building yours, as there are many pitfalls to avoid and I could never cover them all in this article.
Another interesting point is that the same design could be used for fuel storage. After all, fuel is probably the product whose price best reflects the constant inflation of our currencies, and we always need it. Storing large amounts of it would be a wise investment, sure to pay off even in the near future.
The first step of the technique, as was mentioned earlier, is to create a frame to which the cement will be applied. But in fact, for some purposes, this frame doesn’t even need to be made of steel mesh. For the smallest sized water tanks, for example (1 cubic meter/250 gallons or less), will remain structurally sound even without the steel reinforcements as long as their geometry is well designed. This would be accomplished by filling a canvas bag with sand or sawdust, then plastering it by hand with the cement. Once dried, the bag would be emptied and then removed.
But in most cases, steel mesh is used to form the desired shape. Smaller projects (which won’t endure enormous loads) can be completed exclusively with chicken wire, while other will need steel rods with a greater diameter.
The wire and rebar will be bent into the desired shapes, then tied together with steel string using pliers. Some projects will require a poured footing on which to stand, however.
Once the frame is complete, the plastering begins. This is usually done in teams of 2 people. One person presses a trowel or board against the back of the mesh, while the other applies the cement against it. Thus the cement is pressed into the mesh from both sides by the two workers. This process is repeated until the whole frame is covered in cement. Then the cement is left to cure for a few days. Curing must be done slowly however; if the weather is hot, dry and sunny, it may be necessary to cover the project in plastic tarp and even spray it with water to slow the curing process. If cement dries too quickly, it can form cold joints and fail later on in it’s lifespan.
Ferrocement is a relatively new and unexplored technique. The sky is the limit, and experimentation will yield some interesting uses for the future. In the meantime, here’s a list of things I’ve seen and ideas I’ve had:
- Geodesic domes
- Wall material
- Roofing material
- Underground tunnel bracing
- Water tanks
- Grain, food storage
- Furniture (tables, benches, bed frames, etc)
- Boat hulls (already used as such for large ships)
- Outdoor games/entertainments (skate parks, airsoft arenas, stadium seats etc)
- Defensive structures (outdoor walls, road blocks, bunker reinforcement, etc)
- Biogas holding cells
Go forth and experiment!