Monday, October 27, 2008

Rammed Earth Eco-Shed in Norfolk

I came across this video on youtube and had to know more about this project.

When and where did you first hear of rammed earth?
I first heard about it in January this year, it was used as an internal feature wall on a "Build an Eco House in 7 days" TV programme here in the UK. The house itself was primarily timber frame and straw bale, but this feature wall was amazing... I had to have a go!
What was the first rammed earth building you ever visited?
The first rammed earth building I visited was my own! I live in the UK, the chances of you being able to visit a rammed earth building are slim... The Eden Project has a rammed earth visitor centre but that's 6 hours drive for me.
What motivated you to build with rammed earth and not another building method?
At first it was the appearance of the finished walls, then when I realised it was dirt cheap it became the cost, now having single handedly rammed the walls I would say it's the connection with the earth as a building material.. it can be quite a humbling experience at times.
Is there rebar ( steel re-inforcement) in the walls?
I looked at how the Indian communities contructed single storey buildings and decided not to bother with any rebars. I have however added an additional "bond beam" between the roof joist to tie the roof joists together from each side of the 5 degree flat roof.
How did you come up with your soil mixture?
I used a "Soil Triangle Diagram" that I found on the internet, analized my own soil from the footing excavation by using a coffee jar full of water, then you add your soil sample, shake for one minute and the leave on a flat surface for 24 hours, you can then see how the soil has settled. I needed more clay silts so I imported 13 tons of sub soil from 6 miles away near the coast. I then used my invention "Sid the Soil Sieve" to grade the earth down to 12mm 0r 1/2 inch Once blended with 5%-8% cement they appeared to make the perfect soil for ramming.
Any idea of your material costs?
This is a 66m2 building with a maximum height of 2.8m, the budget for the raised footings, additional earth, roof structure and the soon to be planted out Green Roof is a mere £2,700.00 and I'm on track to achieve this budget. Notice that I am building a shed, not a dwelling, and so this was a project on a very tight budget... Pound Zero as I call it. I am a Joiner by trade and work within the building industry, so I see a lot of waste and over-engineering, this shed is just a single story building, and so the need to spend a lot of time and money was not required in my opinion... time will tell if it stands the test of time!
How long did it take to ram the walls?
It takes me about 3 hours to ram each section, each coffin former hold 200mm X 2000mm X 500mm of rammed earth so based on that you could say that it would take 15 hours to ram 1 cubic meter by hand.My Eco-shed has 60m2 of walls so it should take me about 180 hours to ram. But you can double that twice over when you add in the sieving and mixing of the earth, setting up the formers and fighting the elements etc.
Is there any insulation?
I didn't bother with the expense and extra work of insulation, the walls are too thin for starters (only 200mm or 8" thick) and this building is mainly going to be used as a garden kitchen and storage area. Also where I am the weather is pretty good, we have the lowest rainfall in the UK and the winters are mild by comparison the the rest of the country.
What would you do differently next time?
After spending three months researching and many hours designing this building to the last detail... even making scale models, I think that I have got this pretty much nailed down, maybe in a year or so I will see some areas of improvement, but so far I am more than happy with the results. I myself have found the whole experience has made me think a lot about rammed earth construction, so much so that I have decided to write an eBook information manual on building Rammed Earth Sheds this winter... watch this space for more info.

Tuesday, October 21, 2008

Rammed Earth in Modoc County, 1942

This post comes from Flickr member Ken Pollard.

In the early 1940s, my father's parents, Ken and Phyllis Pollard, bought 80 acres about 7 miles south of Alturas, California, next to the Telephone Company's transmission station. Ken worked for the phone company. Alturas is a small town in high-desert country of Northeastern California, and is the first town I remember living in; I was born in 1957. The town’s population was about 3,000 and isn't much bigger now. Alturas is the county seat and the largest town in Modoc County. I can remember when the road out to their house was paved, so that must have happened the early 1960s. The next closest building, a house, was about 2 miles away. On a still evening, you could hear the ‘neighbors’ talking outside their home, 2 miles away. Not distinct, but you could hear voices. It was pretty quiet out there.They built their home of rammed earth in 1942. The first photo shows construction of the house looking just west of north.

You can see my grandfather standing on top of the north wall of the house, tamping at the dirt in a temporary form; he's the figure on the left. Ken had discussed rammed-earth and adobe construction with a professor at the University of California at Davis, so he knew something about it. During construction, they moistened the soil until it would just form a ball when squeezed by hand. The earth for the construction came from the site. They would shovel a six-inch layer of soil into the form, and pack it down to three inches with a large steel tamper, shovel in another six inch layer, and so on. When the form had been filled, it was removed. They could stand on the walls right away. Once, they found that one wall by the front door was crooked. Even though it had just been built, it wouldn't push over; Ken had to take a double jack to it, knock it down, and rebuild it.This wasn't easy work. Phyllis said she thought the blisters she earned building the walls would never go away.They did all the building themselves. In 1989, Phyllis wrote me: All the wood in our home -- bathroom, kitchen, closets, etc. -- was red pencil cedar (not the fragrant) milled in Adin -- 19 miles S.W. of Alturas -- and it is not the cedar that grows throughout Modoc County. Ken just finished it with hot linseed oil and it was beautiful.The second photo is a view looking just south of west; the two figures are atop the same section of wall.

The back walls were full-height rammed earth, while the east and west sides were 4 feet tall. The upper part of the east and west walls were glass. They seemed a lot taller than 4 feet when I was a little kid in the early 1960s. The south wall, which will show better in another photo, was nearly all glass, with a planter area inside.The angled wall in the front of this second photo is the greenhouse area. It was accessed from inside the house, and was full of all sorts of ferns and other exotic (to me) plants. When I saw them in the early 1960s, the panes were somewhat coated on the inside by algae or green mold from years of high humidity. One day I climbed up on that angled portion of the wall, and was sitting up there when my grandmother drove in. She was not happy with me, worried that I might fall through the glass. I felt perfectly safe, as the wall was wide, but was very unhappy to be caught.This is another view of the house, looking west.

Taken a bit later in the construction than the last photo, I think it more clearly shows the greenhouse wall as well as the half-walls on the east-side of the house. On the back of this photo, in Phyllis' handwriting is "Home on Westside Rd. 7 mi. South of Alturas. Under construction."The second photo shows the reverse, that is from the inside looking towards the east.

You can see the half-wall at the right side of the photo. It was glass and post above that when finished. Ken had narrow shelves there, and his extensive collection of telephone-pole glass insulators on display there. The two doorways are the exit, on the right, and the door to the greenhouse on the left.This photo shows the 'front' of the house; we're looking north.

You can see the greenhouse area at the right. My grandfather is standing in front of what will be the glass windows. You can see the long overhang of the roof. In the summer, the wall of glass panes was in the shade, while in the winter, being at a lower angle, the sunlight could come in and help heat the place. Modoc County is cold in the winter, occasionally beating out Alaska for the nation's cold spot.The south wall had floor to ceiling green-tinted windows that looked out over a large grass lawn rimmed with a hedge, sage brush beyond, and mountains in the distance. Inside, next to these windows, was a floor-level planter box, filled with exotic (to me) tall plants. I don't know what they were, but the some of the leaves were big and jagged. In a letter dated 08 January 1989, Phyllis writes --The indoor garden had Gardenia, Bird of Paradise, Camellia, Azalea, Begonias, Rabbit's Foot Fern, and, in a 1 ft. dia. Cedar Bark planter, from floor to ceiling-Stag Horn Fern and Split Leaf Philodendron.When I was a child, I didn't think anything of being warm in a room with a wall of floor-to-ceiling windows, but after I grew up and was out on my own, I wondered about their heating bills. I knew they had a furnace and a fireplace, and concluded that they just burned a lot of fuel. In June 1989, Phyllis told me these windows were 1/4" heat-absorbing glass plate, which explained the green tint and southern exposure I remembered. So, starting in 1941, my grandparents used solar energy to help keep their house warm. Phyllis also told me that during some of the wind storms those glass-plate windows would bend in and out, sometimes as much as six inches in the center of the plate.There was a large, 50-gallon built-in fish aquarium on the inside wall opposite the picture windows. The face of the aquarium was flush with the living room wall. I remember feeding the fish. You had to go into their bedroom and enter a closet door. In this access, the top of the tank could be opened and the fish food poured in. Later, Ken put the gold fish out in the horse trough were they grew to a large size, and they were able to survive freezing solid in the winter.Ken built a large stone fire place in the living room. It was open on the left hand side so that long pieces of wood could be fed into the fire box as they burned. This eliminated the need to chop wood to very short, firebox-sized lengths. A round metal post supported the left side of the mantle.On the southwest corner, near the fireplace, the wall further extended about 6 feet further south, to protect the picture windows from the wind. When this extension was built, Ken took his .22 rifle and fired a shot at that wall. The bullet didn't penetrate.The view from those large windows is shown in the next photo.

My grandmother's notation on this photo reads: "Southwest from house -- Westside Rd., Alturas" so the photo is taken at somewhat of an angle from the house. I think. I'll stick with my sense of direction, since that's how I think of it, and it makes the house layout easier to understand -- but I might be wrong. The last time I was there, I was 11 or 12. I'm now 51 (2008).

Sunday, October 19, 2008

Historic Rammed Earth

Dr. Paul Jacquin has updated his web-page to include more information about the historic rammed earth sites he's visited, and a little more science, with links to his papers and thesis.
The photos of his trip to Nepal this spring are quite wonderful.
His blog is waaaaaaay better than mine, too!

Friday, October 17, 2008

The World's Longest Contemporary Rammed Earth Wall?

Is it possible that this hand-tamped laterite-cement wall near Kome, Chad is the longest rammed earth wall of our modern era?

The entire project encloses a road construction staging yard of about 1.5ha. The total length of the wall is about 500 to 600m. Each "lift" is 6m long by 0.5m tall and the wall is 200mm thick. Eight women ramming and eight men mixing produced about six "lifts" per day, aproximately 3.6 cubic meters of rammed earth or 18 square meters of surface.
About a dozen of the first sections are 3m long. All the rest are 6m, post to post.

Project head Mark David Heath writes:

"I wanted to test the limits of the material here so I built this wall without any footing, at all. The ground was cleared of vegetation and leveled and tamped solid. The forms were set directly on the ground and the wall rammed directly on the ground surface. I know that this violated common construction practice, but I wanted a severe test and quickly. Without a footing the wall has to face the full force of the rainy season. After 3 seasons it is performing very, very well. There is also no protective cap on top, for the same reason. After 3 rainy seasons, the top is only slightly eroded and there is little to no erosion nor softening at the base of the wall."

This project took ten weeks to complete.

Rammed Earth Woodstoves

In Austria, Bertram and Harald Müller of Müller Ofenbau have teamed with Martin Rauch of LEHM TON ERDE to create Lehmo, rammed earth wood-burning stoves.

Friday, October 10, 2008

Rammed Earth In Chad

Reader Mark David Heath sends this report, with colour commentary by REi4E:

This will offer information on a demonstration project of the use of Rammed Earth in Chad, Africa. It is believed that this is the first use of rammed earth in Chad, certainly in Southern Chad and in the recent past. No person, including persons with over 30 years of extensive construction experience in Chad, seeing the demonstration project described here, had ever seen any similar methods previously.

The use of earth in construction is the norm in Chad. Most buildings are built of earthen bricks, often fired with charcoal to increase strength and moisture resistance. (unfired bricks cost about 15 XFA/pc and fired bricks about 25 XFA/pc. They measure approximately 90mm x140mm x250mm or about 3.5” x 5.5” x 10”) The closest similar method, found to be already in the marketplace in Chad, was the use of a manually operated press to take a mixture of earth and Portland cement and press the mass into bricks under high pressure. This press was manufactured in Belgium and imported into Chad. While it produces an excellent product it required a high capital investment (more than $10,000) and delivers a finished product only slightly better, if at all better, than the well produced native fired-brick product. While it is a more uniformly shaped product than the native product, it is still used in hand-laid masonry walls and is dependent on the mortar and skill level of the mason for the overall quality of the final product.

Rammed earth, while perhaps new to Chad, is not a new technique or material. Rammed earth was used to construct ancient structures in Northern Africa, the Middle East, and Asia, with the Great Wall of China being the most dramatic demonstration of Rammed Earth. The ancient structures did not use Portland cement, given that Portland cement is a modern material having been created in the 1800’s. However, Rammed Earth can be well made with the correct soil blend, absent any Portland cement. For example, a known mix is the use of sandy soils with a binder of approximately 30% clay soils. The use of Portland cement has simply made the use of soil an overall easier technique since adding 5% to 10% Portland Cement of almost any non-vegetable soil will produce good Rammed Earth structures. Without the use of Portland cement a higher level of technical and sophisticated knowledge is required to ensure that the mix of sandy soil with the binder of clayey soils is correct to produce a strong and stable structure. In short, Portland cement just makes ‘getting the mix right’ a lot more simple and easy.

The underlying principle with Rammed Earth is similar to the underlying principle in conventional concrete. We are trying to get a mix of materials, of ever-smaller sizes, so that as we mix the materials together, the smaller particles can fit into the gaps between the larger particles. Many will be familiar with the demonstration of a bottle filled with small stones, all of a fairly similar, uniform, size. The bottle appears to be full and one could not get any more stones of the same size into the bottle. However, this same bottle that is so full that we cannot even fit one more stone into it, will receive a very large quantity of sand. We can add sand to the bottle, and by shaking or vibrating the bottle, we can get the sand to fill the voids between the stones. Again, with the bottle apparently now filled to capacity, with stones and sand, we can again add a large quantity of water to the bottle. The water will filter down through the bottle, filling the spaces between the particles of sand.

We are trying to do a similar thing with concrete. We are mixing gravel (small stones), with smaller gravel, with sand, and then with Portland cement and last, with water. The small stones fit within the larger ones, and the sand within the stones. Portland cement is finer than sand and fits within the sand. The addition of the water does two things: it activates the Portland cement, forming a paste that will soon harden, locking everything together, and the water is a surfactant or lubricant allowing the mass to be well blended and formed into the desired shape. In Rammed Earth we are doing the same with soil and clay, which is finer than common soil, or with soil and Portland cement. The clay, or the Portland cement, fills in the voids and makes a more dense mass. Both the clay and the Portland cement also act as binders; when wet they form a paste to coat everything in the mass and then they dry out to harden and lock everything together.

The ramming process in Rammed Earth accomplishes two tasks, one, it consolidates the material making it as dense and possible, eliminating all the air voids possible, so that the material is as well-locked together, physically, as is possible. Secondly, the ramming drives out as much water as possible so that there are not pockets of water that will later evaporate and leave voids and consequential weak spots in the structure. Such voids also allow for future water, such as rain, to return into the structure and soften the clay and allow the mixture to become soft and loose its’ strength, or its’ ability to resist the loads on it.

The accompanying videos show the ramming process used in Chad. In the US, for example, Rammed Earth is commonly carried out with the use of pneumatically powered tampers. These are very fast and powerful and produce excellent results. They do, however, require a power source – an air compressor. The air compressor requires a power source, electricity or hydrocarbon fuel. And all of it requires significant capital investment (Probably well over $30,000, all told). Then the operation requires both the fuel expense as well and the maintenance and repair costs. In Chad, electricity is not common, and it is expensive, as are hydrocarbon fuels. Large air compressors are expensive and rare, and pneumatically powered tampers are practically unknown. Instead, Chad has abundant and inexpensive labor (around $1/day) and an indigenous skill of grinding grains with mortars and pestles made of ironwood. Little girls can be seen grinding grains alongside their mothers as toddlers. By the time they are mature women they have muscles and skills at grinding that are ideally suited to ramming earthen structures. Further, it allows women to work in construction, which is not a common opportunity.

Rammed Earth construction has two primary needs: a good mixture of earth that will produce a dense and stable structure and a forming system that can resist the forces produced by the ramming. As discussed above, the mixture can be accomplished by the right mix of sandy soils with clay soils or, with sandy soils and Portland cement. The forms are another matter. The force produced by ramming is greater than the forces produced by pouring concrete into forms. Hence, common, conventional concrete forms are inadequate for use in Rammed Earth construction, although they can be reinforced to serve adequately.

For our experiment we found scrap steel ‘U’s. These are sheet steel, bent into the shape of a ‘U’, that were originally shipping containers used to ship and protect oil well equipment. These U’s were ideal for our Rammed Earth experiment. First because they were strong enough to resist the forces of the ramming and, second, they were scrap and the price was perfect- free. Last, we took a waste material and turned it into a new, useful product, with a long useful life, which will produce another product, the Rammed Earth structure, also of high quality and long life.

This first project was a wall, about 1.5m tall by almost 1km long, encompassing my employer's construction lay-down/staging yard. We needed some kind of fence or wall and I proposed Rammed Earth, first because my calculations showed that it would not cost any more than the proposed chain-link fence, second, because I hate chain-link fencing (I find it terribly ugly), and last, because if Rammed Earth could be shown to be economically viable it would offer a better and more appropriate construction system to Chad.

In our demonstration we used a soil material known as ‘laterite’, a reddish-brown material, with about 15% clay naturally occurring in it. We mixed 5% Portland cement with the laterite and enough water to pass the ‘ball test’ (see below). Before deciding on 5% being sufficient for our needs, we made test samples of 5%, 10% and 15% Portland cement. The video clip shows the results.

After just a few days we were able to bounce a sledge-hammer off all the samples and decided to go with the lowest-cost mixture. In the future we will attempt a demonstration of Rammed Earth using sand and clay soils. Sand is readily available in Chad and clay soils are commonly used for making the conventional adobe bricks. We made our mix by shovel because it was our decision that it was better to pay 9 men to mix by hand than to use a diesel-powered mixer, at approximately the same cost; better to pay local men to work than to pay foreign manufacturers and refiners.

Counting shovels full of material achieved the mixing ratios. Since we were seeking a 5% Portland cement to 95% laterite mix, we mixed 19 shovels of laterite with 1 shovel of Portland cement. This method of measuring is common worldwide in mixing masonry mortar, just as it is in Chad. The biggest change was to teach the greatly reduced water quantity needed for Rammed Earth vs. the higher quantity commonly used and known in mixing masonry mortar. The test for the correct amount of water is the previously referred to, “ball test”. Taking a sample of material in the palm of the hand and squeezing the material in the hand by closing the hand with muscle force performs this test. If the material will form a ‘ball’ and hold that form when the hand is opened, there is enough moisture. If it crumbles and falls apart when the hand is opened, more moisture is needed. To ensure there is not too much moisture, the ball is dropped from about waist height. The hand is closed on the ball, the hand inverted and then quickly opened, allowing the ball to free-fall to the ground, without a lot of spinning or rotating action. When the ball hits the ground, it should completely break apart. If it holds together, then there is too much moisture. To add moisture to the mixture, water is added with watering cans with ‘rose heads’, or, in other words, outlets with small holes, so that the water is better spread throughout the mix with less chance of mud pockets in the mix. If too much water is added, the mixture can be dried out by adding dry laterite and Portland cement in the same 5% / 95% ratios. A homogenously moist mixture is achieved by turning the pile of materials at least four times with shovels. This process and the ‘ball test’ are shown in the video clips.

We fabricated large U’s from the steel scrap and added screws fabricated from threaded rod to tighten the forms and hold them in position. This can be seen in the video clips. We then added the moistened laterite and Portland cement mix to the forms in layers of a maximum of 15 cm (6”) thickness. This maximum thickness of layers ensured thorough compacting of the material. The material was then compacted by the local women ramming the earth mixture with their pestle sticks. These sticks are made of ironwood and are quite hard. We found that the pestle sticks would grind off and become rounded after about a week, and that by taking a saw and trimming them off square again, we achieved significantly better compaction results. The women have been all their lives grinding grain with these pestle sticks and have well developed muscles and techniques.

Not the least of the techniques that assist in the ramming is chanting. The women chant in melodic rhythms and tell stories all day long, as they go. The chanting gives them a rhythm to pound to, increased camaraderie and reduces monotony with the tales they tell. Our experience showed us that few were the men that could pound all day long and keep up with the women, and none were able to do it for a week. The women would ram 8 hours per day, 6 days per week, for weeks. Half of the women were nursing mothers, and older siblings would bring the nursing children to the work site 4 or five times a day to nurse while the women were taking a break and/or eating lunch. They would nurse their babies before 7, as they were having breakfast of tea and cakes. Then they would ram until 10 and take a break of tea and cakes and nurse the babies. They would ram until noon when we would provide lunch and when they would again nurse the babies. They rammed until 14:00 when they had another tea break and nursed the babies, then finished ramming at 16:30 and went home to nurse the babies and fix dinner. When we first went to recruit the women, we were met with incredulity. The village chief and the husbands could not believe that we wanted to hire the women to "pound dirt". But, since we were paying them, they laughingly agreed.

The folks from the village came out to watch and spent the day laughing at the idea of "the crazy white man" to pay their women to pound soil into a wall. They were all very certain that it would fall down as soon as the forms came off. At the end of the day, when we stripped the forms, there was total silence. They were literally dumbfounded that the wall stood. After 4 days when we hit it with a sledge-hammer and the hammer just bounced off, there was no more laughing at the "crazy white man" and is "dirt wall". I am attaching a short video of about a dozen men trying to knock the wall over.
After they saw it would stand and was resilient, they then said that it could just be pushed over. So, after a couple of weeks, when it was good and hard, I let a dozen of them have a go at it. Then they said that the torrential rain of the rainy season would wash it away. By then, we had already had a chunk of the wall sitting baptized in a bucket of water for almost 2 months, so I knew that the rains would not be an issue. Now, three rainy seasons later, and no degradation to the walls, we have no more naysayers.

With this demonstration we have now introduced a high quality, faster, lower cost building system to Chad. The Rammed Earth uses less Portland cement than even traditional fired-clay bricks when laid with Portland cement mortar. It is faster than the brick method, and cost us about ½ of the market price for a brick wall. Further, it allowed women to work in construction. We were able to involve women without crossing traditional sexual boundaries by having the women use their ‘women’s tools’ of pestle sticks to do the ramming.

A hidden agenda for using the women is that they are simply better workers than the men. They come to work on time, they do not get drunk on the weekends. They do not give us trouble during the day and get into fights with one another. And, when we pay them, we know the money will all get to the house and not end up with much or most of it going to the local bartender or prostitute. The women use the money to feed and clothe their families and to pay for their children to go to school, since there is no free public education in Chad.

Our next steps will be to demonstrate Rammed Earth with clay soils and sand, since laterite is not widely available in Chad. We are also planning on demonstrating construction of a single-story building and, then, a two-storey building. These next steps will offer a broad enough demonstration to make the Rammed Earth system something broadly adaptable to Chad. We need to figure out an improved forming system from readily available materials, to complete the introduction of the system. We would also like to find a permanent and appropriate roofing system.

A quick note on insulation might be of interest. We rammed the walls about 200mm thick (8”) and that is just enough mass that the heat of the day cannot quite make it thorough. You can go to the walls in the heat of the afternoon and the Southern exposure will be very warm to the touch. But the Northern exposure, which has not seen the sun, will be obviously cool to the touch. We would like our future roofing system to compliment the excellent performance of the walls so that they are durable, appropriate, sustainable, inexpensive and well insulating.

With our first demonstration completed, we are well pleased with the results, and have received excellent reception by those who participated and those who have come to observe.