We’re putting a new addition on the southern wing of the house here for the volunteer’s quarters. Right now we’re mostly interspersed on the first and third floors of the north side, but it’s quite crowded.
My room is going to be the one on the corner. Here are a few photos and videos of the process.
Introducing: the world’s first scrap wood bin made from rammed earth!
Talking with my parents about the work I’ve been doing, I realize I’ve yet to really explain a lot of details of what we actually have available, what the infrastructure is like here, and why we think rammed earth may be our best material option.
It may be that a lot of people think, as I did before arriving here, that Surkhet is a small village surrounded by rice patties and without any infrastructure. This is not quite the case, but only 20 years ago this was exactly the situation. The nearest city – Nepalgunj- is in the Terai, to the South on the border of India. Two decades ago, Nepalgunj supplied almost everything that ended up in Surkhet, and these goods were taken over the mountains to the Bheri river, which is where we cremated Rana, about 30 minutes away. Today, there is a huge suspension bridge connecting the two sides, but its used to be that anything crossing the current would take a sedan-sized cable car, and continue on from there, likely by foot. No one but the Tharu people lived here, because of their inherent resistance to malaria. But 15 years Malaria was eradicated in the area and 5 years later a civil war broke out, and a flood of immigration from the mountains to the valley began.
The result is that the city is a mix of the modern and the primitive. The roads are atrocious and its impossible to find a size 11 sandal or Philips head screws in town, but there is a state-of-the-art Washing Machine store in town and internet available at speeds comparable to home. Cows, goats, and chickens wander the streets as cars and motorbikes honk and swerve around them. The edge of the road is a zigzagging, chipped and fraying mess. Every forty feet is a shack as large as a luxurious doghouse, from which women sell snacks and miscellaneous toys that someone sold them for pennies. There are also plenty of food carts that sell chaat, a delicious mix of spices are chickpeas. Surkhet is huge, though, and if you go 1 km out of the center of town, you’ll find yourself waste deep in rice.
I am absolutely shocked by the lack of any goats, chickens, or cows in this video.
When it comes to construction here, brick and mortar is used 99% of the time. Occasionally, you can see structures built from mud packed around a bamboo frame, but these usually predate the advent of decent roads from Nepalgunj, which has half a dozen brick kilns, to Surkhet. Wood is prohibitively expensive, and most workers are only familiar with masonry. Building are typically design like the one below- unpainted, unplastered, and windowless on their sides in anticipation of neighbors building next to them, and entirely made from right angles to maximize the interior space available by building straight over to the property’s edge.
For the Kopila Valley’s New Campus, we’re determined to be as sustainable as possible. This calls for using local materials, local labor, and an intelligent design.
A lot of “green” building projects produce their own energy, but the greenhouse gases released in creating the structures and even building the actual power generation devices tend to imply a long-term debt to the carbon bank. That is, it may take 15 years for a carbon-neutral building to produce as much energy as was used to create it. What if we could make a campus that starts with almost no carbon loan?
This is where Rammed Earth comes in. Sand from the Bheri river, clay from the very soil beneath our feet, and labor from a few dozen workers. If the project is a success, we can give the valley an example of alternative building techniques and possibly jumpstart a new industry.
The process is actually quite simple, but needs to be done precisely to obtain a strong and lasting result. A mix with a composition of 70% sand/gravel and 30% clay/silt is ideal, but playing with types of clay, grain sizes of sand and gravel can give varying recipes. Water is added to the mixture until a ball dropped from chest height shatters on firm ground without exploding. The mixture is then poured into a reinforced mold and firmly tamped until it has halved in thickness. The molds can be made from plastic, metal, or wood, and the tamping process can be mechanized or done by hand. Polymer meshes and rebar are usually inserted to the earth to provide tensile strength against seismic activity (earthquakes). Walls are always at least 12″ thick, and usually up to 18″ or more. The molds can be removed as soon as tamping is finished, which is often done in 6″ intervals that compress to 3″. Once one layer is tamped, another can be immediately added on top. With enough molds and hands-on-deck, you could build a classroom’s walls in just one day.
Instead of rambling, I’ll just copy-and-paste a “Why Rammed Earth?” document that Terri an I wrote for Maggie to give to her board. I have no doubt that it will format horribly.
Rammed earth as a material:
Rammed Earth is one of the oldest building practices in the world. Its components: sand, clay, and water – are commonly available in almost any environment, and when done right, rammed earth buildings easily outlive the lives of a carpenter’s great-grandchildren. Some of the oldest surviving structures are made from Rammed Earth (RE).
The ruins of Yin in Henan province in China have rammed earth
foundations. The use of rammed earth in China dates to 5000 BC.
Portions of the Great Wall of China are made of rammed earth.
Casbah Caid Ali, Morocco
How it’s done
1) A foundation is laid
2) Strong and precise formwork is built and placed on the foundation
3) A mix of sand, water, and clay are poured into the formwork in 6 inch-depth intervals
4) This mixture is tamped and rammed to 50% volume
5) Once the desired wall height is achieved, the formwork is removed and left to cure
A simplified diagram of the process
Benefits of rammed earth
-Strength and durability
-Ease of construction
-Minimal Embodied Energy
Strength and Durability
In contemporary construction, the principles and composition of RE have remained relatively unchanged, but the industry has developed a stronger scientific understanding of how to create more durable and seismically resistant structures. Common modern practices incorporate rebar tie rods, high-tensile strength polymer meshes, and even cement to stabilize the walls. These techniques, when topped with a lightweight second level and ceiling, create a structure that is highly resistant to structural failure during seismic activity.
In the event of a natural disaster, we hope that our campus can serve as a community refuge, and thus it is essential that our buildings can withstand the tests of both time and nature.
Most RE structures can achieve an 800 psi compressive strength without any sort of stabilizer. With a stabilizing agent such as cement, strengths of over 3000 psi are possible, but at the cost of comfort – RE walls without stabilizer are extremely effective at maintain optimal humidity levels and temperature. With lightweight first level ceilings and second level structures, no stabilizing agent is necessary.
Ease of construction
With a sufficient supply of formwork and working hands, rammed earth can be a time efficient building technique. Once formwork is in place, tamping and ramming the earth proceeds rapidly, at six inch intervals that are compressed to three inches. As soon as the mixture has compressed to 50 percent volume, the next layer can be added. Walls can be built to full height in a single day, and take approximately ten days are fully cured and load bearing.
Minimal embodied energy
Without cement, the carbon footprint of rammed earth construction can be the lowest of any building technique. The formwork can be built on-site, with buildings designed to utlize the same forms. The actual process of ramming is done entirely by hand, without the need for pneumatic or mechanical rammers. We can use local sand from the Bheri River, only 15 km away. Clay is typically the most expensive component of rammed earth construction- our site has sufficient clay to construct all of our buildings. This implies absolute minimal carbon output – minor transportation energy, and a nearly non-existent footprint during the actual construction process.
Rammed Earth buildings can give the impression that they “grow out of the ground,” especially when the soil used is taken directly from the site. This may be slightly romanticized, but there is little doubt when looking at a RE wall that its composition is unprocessed, unfiltered, and entirely natural.
A wall is rammed in 6 inch intervals that show up as horizontal striations once a mold is removed and the wall has cured. This effective is especially dramatized when different clay and sand colors are used for various layers. In fact, these layers don’t even need to be straight – graceful bends can be added in that don’t reduce the wall’s strength. Additionally, shapes can be imprinted or “stamped” into walls to serve either practical or aesthetic purposes.
In Surkhet, monsoon season is prohibitively hot and humid for an effective learning environment. Conversely, winters are dry and cold. Building with RE, and incorporating intelligent passive solar designs, combats both of these issues. An 18-inch wall of RE acts as a 12-hour thermal flywheel and is extremely effective at mitigating diurnal temperature fluctuations between day and night. This thermal mass, combined with appropriately sized overhangs, will keep classrooms warm during winter months and greatly reduce indoor temperatures during the summer. The walls also breathe, especially without a cement stabilizer, and maintain a comfortable air humidity around 40-50%. We want to create classrooms that are comfortable during every season – indoor spaces where our students can learn without the added distraction of an uncomfortable environment.
Rammed Earth for our Site:
One of our principal goals for this project is to set an example for the surrounding community and beyond. Some resistance to RE is that building with earth is often regarded as an indication of poverty. Indeed, most RE projects are less expensive than brick and mortar. A successful project using RE will help to dispel this illusion, as well as prove the material’s effectiveness in Surkhet’s climate.
Success in Nepal:
Naomi and Narayan Residence
ABARI Learning Center under construction
Projects around the world:
Nk’Mip Desert Cultural Center
British Columbia, Canada
Sources for further information:
Scientific study done by Geological Society in London (2006)
FAQ list. A quick read through basic facts.
The bomb diggity.Amazing photos and descriptions of his technique. Fun to read. The finished product is amazing, and the author (David Easton) goes through the whole mixing, pouring, and ramming processes step by step.
Same David Easton fellow. Answers a few key questions in detail on this website. He’s very articulate.
Scientific article, study from University of Clug-Napoca in Romania. Some interesting studies about compressive strength depending on sand-clay-cement ratios.
Company that sells clay based plasters and paints, which allow wall to continue breathing.
Some more home photos of RE stuff:
I also have a bit of exciting news. Our visit from Nripal Adhikary, one of Nepal’s biggest RE experts, was very fruitful. He’s a bright, resourceful, and enthusiastic young guy, and he loved what we were getting up to and looking at our massing plans.
We made some sample bricks with him, and discussed in depth the process to build our buildings from earth. He agreed to come on board with us, and also offered to train the two of us, with 5 of our crew leaders, by inviting us to spend 2 weeks working with him just outside of Kathmandu. An amazing opportunity! I could hardly be more excited. Once we return (middle of December), construction of the school will begin in earnest. Soon, this picture will be quite outdated: