Coating Earthbags with Paper-Adobe-Lime stucco

Loading one of two 1,100 pound bales of shredded, recycled paper into the big blue beast. The local city agreed to sell me a literal ton of paper for $41 including loading it. The public works department was very supportive of my intentions to make paper adobe out of it, and wanted samples and pictures… My project is miles from town and not subject to building codes, but I’m glad that even where codes are applicable, folks in city governments are interested in alternative construction.

The tow mixer looks tiny compared with this big blue van. It’s doing double duty as tow vehicle as well as storage container for 2,200 pounds of shredded paper, tools and supplies. At one point it was my ‘back up plan’ as a mobile house truck- I had insulated the walls and floor, put in a composting toilet, bed, dresser, cook stove, shower and took it on the road for a few months. Now its the only vehicle I’ve got capable of hauling a ton of anything, plus it keeps the shredded paper from blowing away, which is nice. (side note, as of summer 2008, I’ve removed the transmission from the blue box as it was needed in another vehicle. It’s just a big blue storage box now.)

Tow mixer filled with shredded waste paper. The mix we used was 90 gallons of shredded paper lightly packed into garbage cans, 63 gallons clay-based soil from the site, 12 gallons lime putty made by mixing one 50lb. bag of type S hydrated lime with water and letting stand for at least 48 hours before use, 2 four pound boxes of Twenty Mule Team borax, and enough water to achieve a thick mix appropriate for spraying with the Tirolessa mortar sprayer.

Here’s the pulped mix, ready to be applied to the walls.

So you can see how stiff this mix is, here’s the tow mixer with most of the mix still in it, and a 3 gallon pail. At first we were making slurry but because we decided to use a Tirolessa mortar sprayer, we reduced the water content and made a pastey muck instead. The mortar sprayer calls for a mix as thick as toothpaste and worked well eventhough we had to scoop the mud out of the mixer with pails because it was too thick to flow out the 3 inch diameter ABS drain port. The mix was so perfectly pulped that we couldn’t see any paper fibers at all.

Blowing the paper-adobe-lime-borax mix onto the walls! We’re using a Tirolessa mortar sprayer which basically is a stainless steel hopper with four air nozzles at its base to push the mix at high velocity. We’re using a 5.5 horsepower gas powered air compressor which I bought two years earlier when I was building a pneumatic-over-hydraulic 20 ton press for making rammed earth block. There is a new stucco sprayer for walls with a wrap around handle on the back of the hopper. It looks much easier to use.

We used a four wheel dump cart instead of a wheel barrow because its easier to manuever on the job site, and doesn’t require lifting during transport of the cart. Here we are using it as a vat to hold the paper-adobe mud and dip into it to fill the hopper on the Tirolessa sprayer. Bill, seen here, got a real sore back and shoulders from using the mortar sprayer.

Eventhough I attached a padded shoulder sling for the sprayer, it was tough to keep that much weight held away from the body, over and over and over… The hopper on the Tirolessa can be emptied in as little as ten seconds, so there was a lot of back and shoulder strain involved due to the repetitive bending to fill the hopper on the sprayer, and holding the weight of the filled hopper out away from the body at the end of the wand.

A couple nights later I thought up a strange idea: take a back pack frame with associated strapping and pads, bend a piece of rebar and attach it to the back pack frame. Suspend the mortar sprayer from a bungee cord to reduce back and shoulder strain… I put this thing together in less than twenty minutes on the job site, Bill wore it for seven hours without fatigue.

Back view of Tiro-YoYo counterbalance rig in action. We called it the Tiro-YoYo because it suspends the Tirolessa mortar sprayer like a yoyo.

Dipping the hopper of the mortarsprayer into the tow mixer when we had a thinner mix, an actual slurry- when thin like this, it flows out the nozzles of the mortar sprayer before you can get close to the wall and pull the trigger, and at least a quarter of the material ends up on the ground. Side Note: A mortar sprayer is generally suggested to be used by young guys in training, but Bill was able to comfortably work a seven hour shift with this unit eventhough he’s been retired for some time.

Monsoon season brought not only torrential rains, but a whole lot of lightning- which causes nitrogen to be released into the atmosphere which falls with the rain water. That’s free fertilizer, and the grass here grew to heights of about eight feet high and so dense you could only get through it really with a machete. This photo is on the approach to the construction site, the van is about ten feet tall.

We got tired of standing around waiting for a garden hose to fill the tow mixer, so I resurrected the system I used about ten years ago when I first got into papercrete and paperadobe. A second stock tank is placed on a small rise and I put a stock tank float in it, (kind of like the toilet bowl float that keeps your toilet tank topped off). Then I attached a 2 inch diameter pipe and valve- the valve is bright red in this photo.

Here the valve is being shut off. Using a 2 inch PVC pipe, the tow mixer fills in about two minutes.

The last section of pipe isn’t glued into place, thus allowing the fitting to be pressed into place when needed, and pulled loose and set aside when the tow mixer is full.

A close-up of the pvc valve and permanent assembly, connected to the second stock tank. Our fittings leak, we might fix that someday.

Here’s the stock tank float in action, note the water tumbling out of it. There’s a piece of black hose feeding it, and the red float is disengaged and therefore allowing water to fill the tank until the water level raises high enough to shut it off.

To keep water and slurry from leaking and sloshing during mixing with the tow mixer, Bill figured if we used a sliced section of a car tire inner tube as a big rubber band, we could cover the seam and hold the lid on. It works great and we can drive the tow vehicle more quickly, and don’t loose any of the mix due to sloshing.

A close-up of the ‘rubber band’ bridging the seam where the plastic tank was cut off.

We realized there was a lot of schlepping of buckets so we bought a second four wheeled dump cart and towed the mixer up onto ramps so it would be high enough to empty into the carts from the dump valve. While one cart is being emptied, the second one is being filled– this cut down on the labor and frantic attempts at trying to keep up with the mortar sprayer and Bill’s incessant demands for more buckets of mud. (This was before we went to the ‘stiff mix’ which required –sigh– schlepping with buckets.

The lid comes off the tow mixer.

We tried applying the mix by hand, with rubber gloves and found that whereas the mortar sprayer is fast, it applies only a very thin coat. We would have needed to spray each section of wall about six times to fill the contours of the sandbag walls so we decided to put away the mortar sprayer and get out the rubber gloves.

Here’s the difference: upper portion was blown on in three coats with the Tirolessa mortar sprayer. Below, the stucco wire and contours of the sandbags can be filled in a single pass when done by hand, tremendously cutting down on the amount of time spent going over the walls. Plus, it just feels right to apply thick mud by hand; its satisfying. This coat will be ‘scratched’ in order to allow later coats to bind with it better; that’s why the base coat is referred to as the scratch coat in traditional stucco work. I realize putting mud on this thick will make it more prone to cracking and that it should have gone on in thin coats, but because it does contain lime and adobe soil, any cracks should re-soften when another wet layer is applied, allowing them to flow together and become mended. Traditionally, lime plasters self heal most cracking through a process called autogenous healing, a process common to earth and lime construction.

I’ve had a hand operated hoist on my old ’47 International for a couple years now. Because my own back went out during this project, I decided to extend the boom arm of the manual hoist and attach a powered cable hoist to the boom to aid in lifting buckets of dirt and lime putty. My aging team of sandbag fillers and bucket lifters was complaining and straining so much that I figured the investment of a couple hundred dollars and my time to rig labor saving devices like this would ultimately offset the work stoppage caused when everyone quit or hurt themselves. Plus, I had been doing everything myself and was happy doing it, but then I slipped a disc in my back and was unable to do a darn thing, so hiring people became necessary, and I figured if there were ways to speed the process while making it safer and easier, I’d save money and maybe even get the job done before the building permit ran out.

Bill guides a bucket of dirt toward the tow mixer using the controls of the hoist for up/down. Rotation of the boom is done manually.

The bucket hits the lip of the lid and tips into the mixer. The electric hoist is 110 volts so its run through an inverter connected to a deep cycle battery.

The empty bucket returning to the ground as the cable is extended in preperation for connecting to another filled bucket of adobe soil.

Wide shot of the dirt filling station, including the secondary stock tank used to speedily fill the tow mixer with water. This is up near the front of the parcel of property, which is several hundred yards from the building site. There is power to the property line but the necessity for a few power poles makes getting ‘real’ power to the house an expensive proposition. I plan to use solar and wind power, or even a good generator for powering larger shop tools. There’s always the option of producing methane from a garden waste digester and converting the generator to run on that.

Here’s a section of wall with a pilaster/buttress at the far right. Damp ‘stucco’ blends in seamlessly with the edges of dry stucco. Damp section lower left.

This is the same section of wall while the earth bags were still mostly uncovered with the adobe based ‘stucco’, (This stucco coat could perhaps more appropriately be referred to as a render coat.)

Here the walls and buttressing pilasters have been finished, and the roof structure is underway.

Above: the finished roof

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