Earthbag Technical Report from Nepal

Good Earth Nepal has published this PDF on its site.

Before presenting some highlights I would add that there are a few details which, to my understanding are only correct in the context of typical above ground houses, less so with bermed or underground structures.

“At present, there are over 15,000 Earthbag buildings worldwide with recent Earthbag  constructions gaining approval under strict US building codes.

An estimated 55 Earthbag structures built in Nepal survived the 2015 earthquake, in regions ranging from Solokumbu to Sindhupalchok to Kathmandu.

… The main material of an Earthbag structure is ordinary soil obtainable at the worksite.

… A study by the U.S. Federal Highway Administration found that the half -life of polypropylene fabrics in benign environments can be 500 years or more. The
bags themselves have a tensile strength even higher than that of steel, and can resist circumferential forces generated from the weight above.

… An Earthbag building uses its own weight to anchor itself to the rubble trench foundation. Since the superstructure is not attached to the foundation by bolts or rebars, the foundation and the
superstructure are able to move independently minimizing the shock transfer to the walls. A rubble trench is also built of individual units rather than a continuous beam further absorbing the shock.

Earthbags are resilient. As per an experimental study on vibration reduction … Earthbags have a relatively high damping ratio with horizontal as well as well as vertical vibrations effectively reduced.

… All of these components make Earthbag structures extremely earthquake-resistant. Tests done in accordance with IBC standards have found that Earthbag construction far exceeds Zone 4 standards, devised to protect against the very highest level of seismic activity. Numerous Earthbag structures have been built in the United States. Earthbag structures are permitted by the California Building Code, the toughest in the United States due to high seismic activity.”

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Earthbag Cellar: Level 6 and 7 Done

After finishing level 6 we ordered another batch of sand (another 6 cubic meters, like the first batch).

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… and it was delivered just as we were getting started on Level 7 (because of tricky vehicle access to our property it came in two batches of 3 cubic meters) … this is the second batch being delivered with the first one in place:

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Layer 7 was relatively smooth sailing … that is with uninterrupted and continuous bag laying … also the overall wall length is shortening as both of the retaining walls are starting to shorten:

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This weekend I was alone and so could not progress with construction so I focused on preparing soil for the next two layers (I hope):

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We’ve pretty much used up the entire side-hill that was created during excavation. I pulled down 45 roughly sifted wheelbarrows of soil. You can see the soil pile that I’ve prepared behind the sand pile. That should allow us to make good progress with mixing and packing the next two layers. Its a tough job … and I hope I’ve seen the end of it .. at least for a while. After the next two layers we want to bring in the excavator to do some backfilling and to collect a large pile of soil next to the sand-pile … that should take us nearly to the end of the earthbag phase of this project

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We’ve had a fairly long stretch of work without rain interruption … but that is about to change. I’ve pulled the  plastic that will cover the walls, over the walls … and later today will go out and layout more tarps to keep the site as dry as possible.

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Earthbag Cellar: Level 5 Done ready for 6

Level 5 was already finished yesterday … but today required a bit more preparations before starting level 6.

The central preparation was putting in the plastic moisture barrier around the entire external perimeter of the wall. We spread it out, folded the corner down and covered it with soil to hold it in place … while doing that we also starting a bit more backfilling to cover the earth-tubes. Thebackfilling gave me a sense that the structure is physicall connecting with the place. Also we got a taste of wha tbackfilling would be like … and we look forward to bringing the excavator back 🙂

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Level 5 is also where we put in the 3 velcros to which we will attach electric sockets:

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Some pictures of level 5 … with a glimpse of Rodica, a first volunteer to visit Bhudeva.

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… and all preparations done and ready to go with level 6 … Vasile mounted on Maria with a tube ready to be filled:

20160902_175034… and this final image is dedicated to my father 🙂

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Earthbag Cellar: Working on Layer 4

With the second layer finished we needed to position the inner ends of the ventillation tubes … we had to assemble the corner joints and the parts that oenetrate the wall used cob to continue the slight angle that was already established with the long section of the pipe.

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The days are getting noticeable shorter, and we felt we wanted to be work longer at the tail end of our evening work sessions … so … lights:

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After finishing the third level (we are already more than half finished with the 4th) we did some simple level testing and got very good results:

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20160826_121451We are now settling into a continuous flow of work moving endless wheelbarrows of soil … things are moving a bit slower because we are now two people … things to look forward to: wrapping the structure with a moisture barrier, backfilling, electrical installation working higher up, earthbag arches … stay tuned.

Earthbag Cellar: Ready for 2nd Layer

When we finished laying the first layer of earthbags for the cellar walls we felt like “that’s done … on to the 2nd layer” … turns out that wasn’t the case … instead more preparations.

First we had to do finish the first layer by putting in the retaining walls. That required leveling the soil (by adding more soil and tamping it) and then putting down a layer of gravel (and tamping it). It greatly enhanced our sense of the structure and how it is built into the hill. The retaining walls acts as a funnel which converges on the outer door.

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Then it was time to finally prepare the 50 bricks to hold down the barbed wire (stay tuned to see what these do as we move up the walls) and then to put in the first layer of barbed wire. That went fairly smoothly.

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With one level of the walls fully down we could not loger roll wheel barrows into the structure so we had to finally put down ramps over the two door frames.

The last task was to put in place the ventillaton pipes that would provide fresh, temperature moderated air into both rooms. This required positioning the pipes, creating supporting earth ramps that gently rise from the intake (built into the retaining walls) into the cellar rooms, covering the ramp with sand …

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… and finally connecting and laying down the pipes.

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now we are finally ready to get started with the second layer of earthbags.

Earthbag Cellar: Getting Started

This year’s project is the most ambitious construction undertaken at Bhudeva: an earthbag cellar. Its design process was intriguing and inspired by some of the ideas I discovered in Christopher Alexander’s work … a gradual, adaptive approach, where each step informs the next (instead of having a theoretical master plan) … organically, during the spring months, a specific shape unfolded informed by a specific place behind the house.

Hopefully this will result in a hobit-like space where all you see is a door going into a hill and inside two rooms – one for dry storage and one for more humid storage). It will be completely buried, including a living roof … so that the hill will be restored (though somewhat reshaped) … and the whole space will become a pleasant place to be in and around.

Once we had a design that felt substantial enough we began preparations. This included clearing the site (overgrown with wild prune) which we had to extend twice (beyond what is show in these pictures) to allow a manageable work site (the cut wood pile is much bigger now). Until we had a clearing.

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Then we had to prepare some tools such as the tampers for the earthbags and forms for the two doors (an entrance door and a door connecting the two rooms).

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… and finally, after preparations and some other life-delays … the tractor came to excavate … a powerful and brutal process … and converted the clearing into what we now call the crater.

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In the crater we marked an outlines of the structure to be with some lime … that got washed out in the rain.

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Most of the structure has no foundations … however in the entrance area (the only part of the structure that is exposed to the elements and other life forces) we did put in some foundation to stabilize, to prevent rodents from being able to dig in underground and to insulate. We built a simple frame at ground level and used 8cm insulation on both sides as forms (that stayed in place)

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We borrowed a cement mixer (my first time using one) and filled it in.

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We brought in some gravel and spread it out (on top of some geo-textile to stabilize it) on the site to have a clean work-surface … the concrete we were proud of making quickly disappeared.

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We re-marked the outline of the structures (this time on top of the gravel) … then added a door-frame which gave it a whole new feel …

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… and after some experimentation we were able to lay a first round of earthtubes.

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We have since made more progress and more pictures to come …

We are also going to send out an invitation for people to who may be interested experiencing earthbag construction to come out and lend a hand … stay tuned.