DIY Soil Cement Sectional Floor

I read an article about making soil cement decades ago, possibly from an issue of Mother Earth News. I thought I might want to try it someday. The wood-framed panelized yurt that we built recently was the perfect place for the experiment. The idea of a “dirt floor” seemed to go well with the setting and the unique building. Plus, I could form it in twelve sections, just as the yurt is 12-sided.

Note that this is not the commercial soil-cement used by some highway departments, which uses sand and crushed stone with the soil and cement mix, making it basically concrete with soil added. They might use other waste materials as well, such as cinders and fly ash.

Since I had discarded the article, saving only the “recipe,” I did a couple of tests first. The mix ratio from the recipe was different from what I settled on.  The original recipe called for less cement by volume (5:1) and the amount of water was less. The calculated volume of material for one of the 2-1/2 inch thick wedges was 3 cubic feet. This proved to be inaccurate when using our soil. The loose, crumbly clay soil turned out to need four cubic feet to allow for all the air pockets. So, adjustments were made, settling on a mix of four cubic feet of soil to 1 cubic foot of cement for one wedge.

We divided each wedge pour into 1/4 cubic foot of cement to each cubic foot of clay soil, making a total of four pours per wedge. The water mix would be whatever made it workable, but originally was figured to be less than two gallons.

My first test sample, a very small amount comparable to the 4:1 mix with the water equivalent to the original recipe turned out fine in the test, but proved to be way too dry in the first wedge we mixed and poured. So, the amount of water became an evolving test as we mixed and poured the subsequent wedges. Generally, two gallons per mix worked with adjustments made for damp soils or dryer soils. Even though all the soil came from one pile, the moisture content varied.

I made two tests. I painted one of them with concrete stain just to see how we liked that. We didn’t. The natural color was just the look we wanted for the yurt floor.

Materials needed

This is a list of all the materials and tools we can remember using. The amounts of soil, cement and water needed are detailed in the instructions.

Soil

Cement

Water

Vessels for storing sifted soil

Wheelbarrow for mixing

Shovel

Hoe

Small shovel for scooping and cleaning out last bits

Strong bucket

A variety of concrete trowels, i.e. margin, brick, rounded finish, long finish

Tamper

Fence wire

Plastic sheeting

Tape

Wood and hardware for forms

Step 1 Build the Form

The first step was to make forms. My plan was to pour the wedges from the back of the yurt to the front, every other one. The forms were simply screwed to the yurt deck. They could be easily moved for each subsequent pour. Once six were done and cured enough, then we’d just fill in the final six wedges. The middle was left to put in something fun for a center focal point.

The center was six-sided while the yurt was 12-sided. Due to this, the forms would meet at a corner point, and the center of one of the six sides, thus being different lengths and angles. I made each a little short and used wedge shims to bring them tight. This also made it easier to remove when the pour was cured.

This photo shows how the pours progressed and the form material was moved.

You could use this form system to pour a square or rectangular form by deciding how large a pour you wanted to do for each section.

Step 2 Bring in the Dirt

I brought in what I estimated to be more than enough sandy clay soil for the project, about 2-1/2 cubic yards. I dug it up on our property, but dirt can be found where excavation projects are going on. Just about any kind of earth can be used, as long as it contains clay and sand. It should be free of organic material and debris.

I tested my soil by filling a jar half full of sifted earth and adding an equal amount of water. I covered the jar and shook it for a few minutes then allowed it to stand undisturbed for an hour or so. Once settled, the soil will have separated into layers of sand on the bottom, clay in the middle and silt on the top. The ideal mix is when there is about 75% sand and 15-20% clay. I did several tests and got different results each time. In this photo there is about 50% sand and 50% clay and silt.

Step 3 Sift It, Sift It Good

Once we carved some time between other summer/early fall projects, Robin started sifting. She started by just chopping at the dirt with a hoe, but then figured out one of her plastic greenhouse trays would do the job and give us a more consistent product. After the first pour, we determined that each wedge would require almost 4 cubic feet of dirt. I had built a 12x12x12 inch (a cubic foot) box to measure the volumes. Robin got the four batches ready in advance of each pour by just filling the box with sifted dirt and storing in various holding containers.

Step 4 Mix It Up

The soil went into the wheelbarrow first, then the cement was added in furrows I made in the soil. I mixed that up using a hoe, chopping at it about 2 inches at a time from front to back so that the cement was well dispersed throughout the soil. Dry mixing continued until I couldn’t see any “orange” clay or “grey” cement bits.

Then I added two gallons of water and mixed until we had a batch that wasn’t soupy, but not too dry. We found that the wetter the mix, the better.

Step 5 Get Down and Get Dirty

Since the yurt has a few steps up to it and neither of us have terrific knees, Robin filled the bucket with about three shovel scoops and hauled it up to me inside the yurt. I slopped down the glop and handed back the bucket. One wedge, which was four batches of mix, took about two hours including a break after the wire reinforcement was tamped in after the second pour.

Since we’d have four pours for one wedge, I worked from the back to the front. After two pours, I spread it all out evenly, using a brick trowel to move big blops around and a margin trowel to semi-smooth it all.

Step 6 Start Spreading the Mud

Even though we used the same proportions of dirt, cement, and water for each pour, the consistency varied wildly. After the first couple of wedges, we decided we liked the wetter consistency and I started adjusting the amount of water depending on what happened with the mix. The wetter blend, about the consistency of Sloppy Joe mix, was easier to shovel and work with, plus those wedges were not as prone to cracking, which did happen on several early pours.

Step 7 Add Wire Reinforcement

I had no idea if soil cement cracks the way concrete can, but I figured reinforcement would help by containing the separation if it did occur, holding all snug together. I made a jig to simplify cutting the reinforcement wire, cut 2×4 grid fence wire in three pieces (this made the best use of the material), positioned it carefully, then tamped it into place. It was tamped to get any high ends down and to embed it into the first layer.

I made my tamper from a short approximately 8 inch piece of cedar tree trunk, a hole drilled in it to accommodate a broom handle.

Step 8 Get Back to the Dirt at Hand

While I tamped, Robin loaded the next cubic foot of dirt into the mixing wheelbarrow and measured out the cement. If she had the energy, she also started sifting dirt for the next wedge. We scheduled two wedges a week, weather permitting. We got behind when wildfires in Oregon caused our air quality to become unsafe for breathing, but after a couple of weeks we were able to return to the task. We got rained out a few times as well.

Step 9 Screed It!

Once we poured the fourth batch into a wedge, it was time to screed. I screeded using a 1×3, just as I would for traditional concrete. The “sawing” motion while advancing the screen board forward used in working concrete didn’t work very well. When screeding the soil cement, I found that it didn’t pull along like a concrete mix does. It tended to suck the “mud” from behind, pulling it away from the forms and scraping the surface off behind. The “mud” also built up in front, making it difficult to move it forward. I worked out a method using a margin trowel to remove the material from in front without taking too much.

Step 10 Finish It!

When I got it fairly close, I used a finishing trowels to begin smoothing it out. When working it you can get the surface to pull along to lower areas. Occasionally, air bubbles would develop, and I just punctured them and filled with a little excess mud. When I had it acceptably flat, I used a concrete finish towel to get it smooth. It can be worked to a very smooth surface, but I didn’t attempt to do that.

For the areas between the formed wedges, I taped plastic sheeting to the wedges on either side to keep the mud from adhering to the finished wedges and to keep them clean.

Step 11 Do Something With the Leftovers!

Four cubic feet was just a little more than we needed, so we used metal flashing and clamps to make forms for stepping stones. We added leaves to give them a fun look. I have no idea how they will hold up in the rain and freeze, but I guess we’ll find out!

Sections are still curing, but we might have a pinwheel effect going on here!

In conclusion, a crew of two old fahts did take a few weeks to accomplish soil cementing a 200 square foot area, but it’s a unique and durable floor. Plus it adds mass to the building to help maintain a comfortable temperature inside. I’m working on my middle piece now and will post an update when it’s done!

If you’re interested in how I built the rest of the yurt, we published a book. Here are the links:

Building a Wood-Framed Panelized Yurt, in color

Building a Wood-Framed Panelized Yurt, black & white

Text and photos on this blog are copyright ©2020 by Marvin Denmark and Robin Koontz. As much as we love to share, please ask permission before re-posting. Thank you!

Scaling Up the Size of the Yurt

I want to talk about scaling up the size of the yurt. We had considered adding this in the book but decided against it. So I will take you through the process now. The size or diameter of the yurt in the book was 16 feet. Considering the next reasonable size up one might think of a 20-foot diameter. Let’s follow the steps to creating it. The parts that get affected are the foundation, floor panels, wall panels (though not height), beam length, roof panels, and possibly the skylight (size). If you follow this process you can create a yurt of any size (within reason, as loads on the beams become a factor). We begin with the floor plan, which in turn informs us of what the foundation will be.

With a diameter of 20 feet we are looking for the circumference. That is found with the formula C = d X pi (circumference = diameter X 3.1416). C = 62.83185. With this information we can find the number and width of the wall panels. First, for the number of walls, we divide the circumference by 4. Four feet is the “ideal” working dimension for our walls. When we divide we get 15.7. An uneven number or decimal number doesn’t work well for wall layout. We want an even number of walls, so we round up to 16. Now we divide the circumference by 16 to get walls of approximately 3.927 feet or 3 ft – 11 1/8 in. That’s a good workable number.

chordlengthLet’s step back a second. When we divide the circumference of a circle by assigning a number of sides to it not only do we get our floor panel angles at the peak and the base (more on that shortly) but we also get a dimension that makes for an approximate length for the base of the triangle, which will be our wall length. But this dimension is not the true base of the triangle. To get that you would have to use the chord length formula. There are variations on that formula depending on the conditions known. For us it is the simple one: 2 r sin (angle)/2. We have a radius of 10 feet and an angle of 22.5 degrees. 2 (10) sin 11.25 degrees = 3.9018′, or 3 feet – 10-13/16 inches. This is our most correct length for the base of our triangle and the width of our walls.

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The next step is to find the angles involved in making the various panels. We now have 16 sides around this yurt. In recalling our math classes we know there are 360 degrees in a circle. Dividing 360 by 16 will give us 22 1/2 degrees for the peak angle. The sum of the interior angles of a triangle is 180 degrees so that leaves us 157.5 degrees for the base angles. Since the sides are equal, than the angles are equal at 78.75 degrees. Remember, the peak angle for our yurt in the book had 12 sides and thus (360 divided by 12) 30 degrees with base angles of 75 degrees each. Some people may not like dealing with partial angles, seeking more simplicity in their work. So let’s look at this yurt with more sides, but same diameter, say 18. That would give us angles at the peak of 20 degrees and at the base 80 degrees. Using the chord formula above the wall length will be around 3.49 feet long. That will waste about 6 inches of siding plywood for each wall but is still a workable width.

With the information above we can layout the foundation, and we could finalize the math to build the floor panels. We can build the walls also. If we follow the process in the book you will see that not much changes except for the length of floor joists and later the roof framing members. Walls will stay the same height so just a width adjustment is necessary. I should say at this point that you could make the walls taller to any height chosen, which will only effect a later calculation for the placement for the skylight ring and it’s tower height. So feel free to experiment!

Following this information and combining it with what is in the book you should be able to design your own yurt of practically any size. Just remember the larger you go the more need for paying attention to the loads placed on various members.

Next time I will talk about the beams, tower and skylight, and roof panels for a larger yurt.

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Here are the links to purchase the book:

Building a Wood-Framed Panelized Yurt, in color

Building a Wood-Framed Panelized Yurt, black & white

Building a Wood-Framed Panelized Yurt: the movie

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Robin put together a movie called “How to Build a Yurt in About Five Minutes.” You can view it by clicking here!

If you’re intrigued yet need more information, you can also buy the book in either color or black and white. It’s 176 pages of step-by-step instructions with lots of photos and drawings, and also includes a materials list for a 16-foot yurt:

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Here’s the link to the color version of the book.

Here’s the link to the black and white version of the book.

Building a Wood-Framed Panelized Yurt: the book

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We have a book! Actually, we have two books. Links to purchase them are below. Color printing costs were high on a 176 page book, so we also published a black and white version. The price is about 40% less than the color version, and the photos are clear enough to illustrate the task at hand.

B&WBOOK

Here are the links:

Building a Wood-Framed Panelized Yurt, in color

Building a Wood-Framed Panelized Yurt, black & white

yurtbooks

Building a Wood-Framed Panelized Yurt, Pt. VII: The Book Proof!

Proof

We received the first proof of our book today! A random page opening revealed some of the details for the wall panel jig. There are 170+ pages of everything you’ll need to know to build and assemble a wood-framed panelized yurt.

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There are a couple of drawings to finalize, and a few photos with explanations to add regarding final details, along with some additions and corrections to do. Then we’ll release the book to the world via Amazon.com.

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Meanwhile, here are the Three Yaketeers, with Jeep the supervisor. “Another job, well done.” — Mr. Natural

 

 

Building a Wood-Framed Panelized Yurt, Pt. VI: Floor Plan, Roof Plan and Materials List

Here is the floor plan for this yurt. People who require more details will benefit by purchasing the book, which will be released in September 2018.

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Here is the roof plan for this yurt.

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And here is the almost complete materials list with prices based on costs in Lane County, Oregon. All of this will be included in the book, along with an illustrated cut-list.

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And last but not least, Robin has been working on the front and back cover for the book. Here’s a peek at how it looks now. We’re hoping to finish the yurt in the next two weeks, and will have an updated photo for the front cover. Thanks for looking, and stay tuned!

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Illustrations copyright ©2018 by Marvin A. Denmark; cover design and photographs copyright ©2018 by Robin Koontz. Please do not share without written permission, thank you!

Building a Wood-Framed Panelized Yurt, Pt. V: The Roof Panels

The yurt roof panels were installed by two baby boomers and three Millennials. It was the perfect crew: everyone figured out what to do after the first panel and we were done in two hours.

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First, I explained the process and went over safety concerns.

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I built a little cart to make this part easier. Robin installed handles which also helped make the panels, more awkward than heavy, easier to maneuver.

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Whoosh goes the panel to the scaffold.

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I nailed up each placed panel while the crew brought up more and secured with spikes.

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The entire crew getting the last panel up!

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And the roof panels are up! Next I’ll insulate between them, add more ice and snow shield, and install the skylight dome.

We are writing a book about the entire process from start to finish so we can share how to build this yurt with anyone who is interested! Stay tuned as we progress, and be sure to watch for news on the book.

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Thanks for stopping by! Photos taken by Marvin Denmark and Robin Koontz.

Building a Wood-Framed Panelized Yurt, Pt. IV: The Rafters

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Once the cable is tightened around the tops of the walls and the ring tower is centered, it’s time for rafters. The ends are now cut for the fascia, and the other ends are invert-cut to fit against the corners of the ring assembly.

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I placed each rafter in a corner, then put Robin on the tower and handed up the first rafter beam.

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She held the beam while I climbed the ladder across from her. Nothing is heavy, but definitely not a job for one person.

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The metal ring and the wood ring behind it were pre-drilled, so a bolt was placed and Robin hammered it in. This secures the rafter beam to the ring. The cable through holes in the rafter ends will tie it all together.

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Looking like a yurt now! Next is the cable, then the roof panels.

We are writing a book about the entire process from start to finish so we can share how to build this yurt with anyone who is interested! Stay tuned as we progress, and be sure to watch for news on the book.

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Thanks for stopping by! Photos taken by Marvin Denmark and Robin Koontz.

Building and Assembling a Wood-framed Panelized Yurt: the Basics

I also write DIYs for Instructables.com and just posted one about the yurt. You can find it here: Building a Wood-Framed Panelized Yurt. I entered it in their Tiny Homes Contest so if you like it, please vote, thanks! Voting ends October 1, 2018. I need a new camera. 🙂

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Meanwhile, I’ve been posting more on the YurtYaks Facebook page than I have here, so if you’re curious about the rafter installation and the roof panel assembly, head over there! I’m busy finishing up the book, so will be back soon!

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Thanks for stopping by! Photos copyright ©2018 by Robin Koontz.

Building a Wood-Framed Panelized Yurt, Pt. III: The Ring Tower

After a long, wet winter, we finally got a few sunny days to assemble the ring to the tower and then lift it up! To note, this is a ring for a 6′ dome and we’ll be talking about a 3′ dome in the book. It’s a lot easier to build and manage. This 6′ ring weighed about 200 pounds. As you can see, there’s a 12g metal ring inside (for added strength) that adds to the weight. FinishedRing6-ft

The ring will be temporarily held in place by a tower. Once the rafters are bolted into place, the tower goes away. When I assembled yurts in the past, the tower wood would be salvaged and used for interior wall framing.

Tower-on-Side

Once the components were ready and it was dry enough to drive to the yurt, it was time for installation. The tower was built so I could just take out a couple of screws and then finish assembly on-site. The ring required a neighbor with a strong back to muscle it into its new home.

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You can see the tower parts on the right side of the yurt. I assembled the tower on the inside, given that it would not fit through the door otherwise.

The next step was to attach the tower to the ring…

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and strap it in readiness for hoisting. To keep the bottom from sliding out I attached a cable that laced through the outside legs and bolted to two walls on either side.

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After shoving it against the far wall, I jacked it up about 2-1/2′ to make the angle of the strap going over the doorway and to the truck a little less severe. I installed a cut pipe on the doorway so the strap would slide easily. You can see the cable attached to the wall in this photo.

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And there she is! You can see the movie on our Facebook page or by heading over to this link on YouTube.

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I put small lengths of conduit underneath the tower so that I could shove it into place after determining the center.

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The last step was to turn it so it is lined up to the 12 rafter corners on the walls. Check out the homemade plumb bobs (plummets).

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We’re ready for the rafters! Stay tuned while we once again wait for it to stop raining.

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We are writing a detailed book about the entire process from start to finish so we can share how to build this yurt with anyone who is interested! Be sure to check back as we progress, and be on the watch for news on the book. You can also find us on Facebook.

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Building a Wood-Framed Panelized Yurt
by Marvin Denmark and Robin Koontz
ISBN-13: 978-0692957370
ISBN-10: 0692957375

Thanks for stopping by! Photos by Robin Koontz and Marvin Denmark.