Construction Earthbags

Earthbag Cellar Level 10, 11, 12 and 13 … soon arches

We had one weekend of construction at the beginning of June with the help of Adi and Dan … we got 10 and half of 11 done.

We then paused because of my allergy-period and because we were busy finishing and launching the new Cutia Taranului website. In recent weeks we got back in the saddle, we finished 11 and 12 … and its feeling more and more like a place.

We’ve also put in velcros to which we plan to attach a grain storage and dispenser (planned to hold ~100kg of grains):

Sia, a new puppy who has been with us for a few weeks is getting acquainted with the site … and also has manifested a destructive quality … it seems she enjoyes tearing into earthbags and digging soil out šŸ™

Today we started 13 which brought us to the levels of the rectangular door frames …. which means that soon we begin to form the arches on top of the doors.

And finally we have out overall progress indicator. This pile of soil is like an hour-glass … if my calculations were correct it should have enough soil to bring us to completion. When we started construction this year the pile reached out to where the mixer is currently standing so we’ve taken quite a bite out of it. It is nice to feel the space starting to open up and reconnect with the world beyond it.

I estimate we are going to end up with 19 or 20 levels.

And lastly some number I’ve collected:

  • We are currently mixing batches with a ration of 4 shovels of sand + 12 shovels of clay soil. This fills an 80 liter wheelbarrow.
  • A wheelbarrow is roughly the amount of soil that goes into a sack (1 meter long when flat, 80cm when filled to the max) … though we are using mostly tubes (not sacks).
  • Each batch includes 2 wheelbarrows.
  • Each wheelbarrow contains ~25 cans (3 liters in a can) … so it takes ~25 tosses to “move” a wheelbarrow of soil up the wall.
  • Each batch (of 2 wheelbarrows) translates into ~1.5 linear meters of wall (we are using 50cm wide – when flat – tubes and bags).
  • Which means that each can holds about 3 linear centimeters of wall.
  • At the current rate Iulia and I (neither of us particularly strong) are doing ~2 linear meters of wall an hour (though we will slow down as we move higher up the wall).
  • At this rate we can do a level in 3 or 4 days (we work at most 6 hours a day in two sessions … morning and evening).



Construction Earthbags

Earthbag Cellar Level 8 and 9 and Backfilling

We’ve completed levels 8 and 9 …



… on level 9 we were joined by Itsik and Yifat who visited with us for a week … so we reached and celebrated the end of 9 together.



In level 9 we also put in additional vertical reinforcement by pounding in rebars into the longest stretch of buried wall that we have (~6 meters)Ā  … and we will continue to do that in an interlaced pattern to give the wall some more strength to resist the weight of the earth piling up behind it.


Which brings us to today … soil … we called the excavator back (marking what is probably the half-way point of wall construction) … to start backfilling and bringing some more soil to our mixing station (so that I don’t need to carry it in a wheelbarrow). Yesterday we prepared by pulling the plastic covering over the walls Ā  20161010_095944

.. and so it started … and very quickly the corner behind the first retaining wall was filled up ….


… then the side and rear corner20161010_110123

… during the backfilling, a new soil pile near the mixing station started to appear



… and before you know it (almost three hours later) the backfilling was complete …. so from the outside we are back at ground level (which does make some maneuvering on the walls easier)


… and a huge pile of soil (30+ cubic meters) is now blocking the entrance and hiding the site … when that soil is gone, construction of the walls should be complete (or very close to completion)


As the work progressed we realized we were going through A LOT (= surprising amount) of soil … we’ve used up most of the free soil on and around the site … and it doesn’t look like what we have left will be enogh to complete backfilling and covering the structure. At first this felt like a potential problem … but it quickly transformed into opportunity. It looks like the supply of soil needed to complete this project will overlap and lead into the next project. One option weve been discussing is a small lake (a whole other story). Another option is to start excavating what may be the next construction project … either way … it left us with a pleasant sense of continuity šŸ™‚

Construction Earthbags

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 EarthbagĀ  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.”



Construction Earthbags

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).


… 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:


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:


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):


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


We’ve had a fairly long stretch of work without rain interruption … but that is about to change. I’ve pulled theĀ  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.


Construction Earthbags

Earthbag Cellar: Level 5 Done ready for 6

Construction Earthbags

Earthbag Cellar: Level 5 Started

We decided to incorporate a small cob bench facing a western view (sunsets) – these are the supports built into the wall:




Level 4 is complete and Level 5 has started


Construction Earthbags

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.



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:



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:


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.

Construction Earthbags

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.


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.



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 …


… and finally connecting and laying down the pipes.


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

Construction 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.





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).



… 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.





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


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)


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



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.


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 …


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


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.

Construction Earthbags Earthship PAHS

From Earthship to Earthbags

This is a long overdue post and several external movement have prompted me to finally write it.

A while back I wrote how we moved from hemp construction to Earthships. Well the movement continues and we have moved away from Earthships too. This happened gradually and for numerous reasons:

  1. Expansive Clay Soils – we are proud owners of lots of clay-rich soil which expand when wet and contracts when dry. As I was doing research into Earthships specifically and underground houses generally this seemed to be a problem. Expanding clay soil can place tons of pressure on the walls of a house which can cause it to collapse. So for some time I lived with the question is it possible to build an Earthship in expansive clay soils? My conclusion was that the problems was not the clay soil but moisture.
  2. P.A.H.S – As I did more research I started to come across evidence hinting that Earthships do not work well in our climate (moist and cold). Just recently I came across clear evidence of this. I continued my research and was blown away by an old book called Passive Annual Heat Storage. The book introduced a method by which an underground house is insulated with the soil around it, transforming the surrounding soil into a huge heat battery that charges itself during the warm months of the year and discharges during the cold months. The book confirmed my suspicion that the problem with clay soils is indeed moisture and not clay. The “insulation umbrella” concept described in the book (together with other moisture related strategies) provides a solution to keep the clay soils surrounding the house dry – providing a resounding (even if for now theoretical) answer: yes, underground houses can be built in expansive clay soils by keeping moisture away and in doing so neutralizing the “expansive” quality.
  3. Tires in Romania – we could not find a feasible way to get used tires in Romania.

Empowered by the P.A.H.S knowledge I continued my exploration and started looking into earthbags (it’s a terribly designed and uninviting website but has valuable information). I loved the simplicity and ease-of-construction when compared to ramming tires with earth. I would not have considered it a feasible method of underground construction had it not been for the P.A.H.S. method. I do now.

… and so this is the house that we plan to build.

Of Earth Inside the Earth

The house will be completely buried in the ground except for the south-facing aspect. It’s intended location is on gentle south-facing slope. We will excavate for it into the slope.

Most of its walls will be load-bearing earthbag walls. Hopefully our clay-rich soil (that will be excavated to make space for the house) will provide most of the material needed for the earth-mix that will go into the bags. There is no material more local than earth.

The floor will be an earthen floor and the walls will be covered with earthen finishes.

The roof is an as yet unresolved challenge. It too will be covered with earth and will therefore need to carry a very heavy load (current estimation 1.2 tons per square meter). This weight will probably be supported by round timbers though this is not yet final.


We are planning a house that will be ~200sqm. It is designed to spaciously accommodate a small family. It will have a main part and a smaller, attached living space for additional privacy.

P.A.H.S. – 21 Degrees Celsius All Year Long

Thanks to the P.A.H.S. insulation umbrella the house will (after 2 or 3 years of acclimatization) eventually settle on a steady all year-long temperature of 21c. During the warm/hot months excess heat will be stored in the huge earthen thermal battery. During the cold months heat will be drawn from the thermal batter.

This means that we will not need any additional energy input to keep the house warm. Even the water supply that runs under the insulation umbrella arrives at the house at 21c which means that less energy is needed to heat water.

The temperature of the house is a function of how much heat gets into the house (which depends on how much windows it has) and how much it can store (depends on numerous design factors). It is nearly impossible to change the temperature of the house after has been established. Any attempt to heat it will be futile because the energy will be drawn into the thermal battery surrounding it and you would need to invest a huge amount of energy to change that.

Imagine not having to cut down a single tree for heating!?

Rocket Stoves

We do expect to have at least one rocket stove for comfort … to boost the temperature to 23 -24 degrees when we want to … and to heat water during the months when solar-heated hot water is not available.

Ā Ventillation

ventilation is, we’ve come to believe, an important and often missed aspect. The air in the house should be regularly exchanged. Fortunately the P.A.H.S. strategy includes a passive ventilation system (no fans and no electricity to run it) that brings fresh air into the house all year-long at, you guessed it, 21c. The ventilation system also plays a key role in storing excess heat when it is generated (summer) and retrieving it when it is needed (winter).

The trick (and the one challenge that still worries me) is to build the house air-tight. You should not need to open/close windows in this house ever. During the summer months the passive ventilation system will draw hot air out and store the heat in the thermal battery (instead of letting it escape out windows). During the winter months the passive ventilation system will draw air in from the outside, running it through the thermal battery and bring it up to room temperature.

Imagine fresh air during winter at room temperature (and stale air removed) without losing heat to the cold outside!?

Passive Refrigeration

Michael Reynolds in his classic Earthship books points how ridiculous refrigeration can be: we build boxes to keep the cold out, spend energy to get those boxes warm then build smaller boxes inside and spend more energy to keep those boxes cool.

With a slight change in configuration, the same passive ventilation method that is used to regulate the temperature of the house can be used to create a cool space (let cold air in and warm air out). In the Romanian winter that cool is cold enough not just to refrigerate but also to freeze.

Our intention is to build an insulated (from the warmth of the house) space within the house that will harvest winter coolth. That coolth will be stored in water bottles that will freeze. The space will be divided in two. One part will hold a freezer that will be exposed to the natural freezing temperatures. A second part will hold a refrigerator. Both will be unplugged during the winter months. When spring sets on and the ice melts and there isn’t enough coolth they will be plugged back in and run on electricity (which is once again available as the days get longer and the sun shines through).

Photovoltaic Electricity

We would like to be able to live off-the-electric-grid. The first step towards doing that is by drastically reducing consumption:

  1. The house is naturally heated so that no electricity is needed for heating.
  2. Hot water is pre-heated due to the thermal battery, then heated with an efficient rocket stove during winter and with a solar-hot-water panel in spring/summer. Very little electricity needed for pre-heating small quantities of water.
  3. Refrigeration is designed to work on the naturally available coolth of winter when there is very little sunshine to produce electricity.
  4. Large south-facing windows and a one-room-depth house design provides plenty of natural light all year-long.

This leaves us with some lighting and other smaller electronic devices (computers and such). This should enable a photo-voltaic system that will provide all our needs in summer months and most of our needs in winter months.

Attached Greenhouse

The front of the house will be a large greenhouse that will serve multiple functions:

  1. Harvesting heat during winter months.
  2. Extend the growing season.
  3. Growing plants that can not tolerate the harsh winter (lemons? avocados? even bananas?)
  4. Having a pleasant green space to spend time in during the cold winter months.
  5. Consuming grey-water created in the house (this is much easier for us since we use composting toilets and do not have to deal with black-water).
  6. A transition space between the outside and inside (keeping the inside cleaner).

Rainwater Harvesting

For a long time we were faced with a dilemma:

  1. A standard roof that will harvest rainwater for the house but somewhat compromise insulation (all heat inside the house rises) and durability (all mechanical roofs are prone to deterioration and require maintenance).
  2. A living roof that will provide superior insulation and durability but is practically useless for harvesting rainwater (10-15% of a similarly sized regular roof).

After long deliberation we came up with a solution that will provide us the best of both worlds. The house will be built with a living roof (a relatively massive one) that will complete the insulation umbrella.

We will be building a “mirror” structure of the house slightly uphill. This will be a simpler and cheaper structure. It will include a workshop, storage spaces and an open yet sheltered work space for a summer kitchen and other outdoor activities (some of these functions are now unmet or just temporarily resolved). This second structure will have a metal roof for harvesting rainwater that will be stored in an underground cistern that will supply the main house.


None of these technologies are new. All have been implemented in one way or another. We do not yet know of a house that has been built using all these technologies combined in a climate like ours. It has taken almost 3 years of research by trial and error to reach this formula which has the potential to be an affordable, ecological, sustainable and scalable method of construction.

Scalable is an important quality worth explaining. From what we’ve seen most eco-houses fall into one of two groups. One are small hobbit-hole-like homes which are often the result of do-it-yourself builds with natural materials (these do not scale up very well). The other are large and expensive homes that rely on expensive and complicated technologies to achieve an illusion of sustainability (that often ignores their embodied energy and their technological dependence). We are trying to create something that is in between these two worlds. The P.A.H.S. method can be applied to any size home and it is a core component in the overall efficiency of such a house.

This will hopefully be a very-long-term house.