The great thing about cob is its low-tech nature. You don’t need many fancy tools to work with the medium. Cobbers thumbs are useful wooden hand tools for pounding cob into place on walls, and “stitching” the material together. The fat, blunt ends are good for the pounding, and the pointed ends are useful for weaving different layers together.
You can make these with any old scrap wood. I made these from a downed black locust branch, using just a utility knife and a bow saw.
Progress on the cob house has been continuing at a good clip. The second course of the foundation has been laid out. We started to run out of larger pieces of urbanite, and fell back on medium and smaller pieces, which I thought to be less than ideal. Unfortunately, the majority of the urbanite I have collected is very irregularly shaped, so it’s trickier to work with than flat stuff. I think it will be fine, though.
We started to fill in the cracks between urbanite with more clay/sand mortar. Whenever there is rain in the forecast, I throw tarps over the entire foundation to prevent it from getting went. The mortar would probably just wash away if it got thoroughly soaked. But anyway, the purpose of the mortar is to prevent the passage of wind and rodents into the living space. Eventually, the interior face of the foundation will be cobbed over or plastered over to for extra protection.
Yesterday, my first work exchanger arrived. It will be fun to have new help around the work site.
On Friday, I hope to get sand delivered, because I expect cobbing will begin within another week… yeehaw!
The first course of the foundation is now pretty much complete.
Unfortunately, I had nowhere near enough urbanite that I thought I needed, and I made another trip to collect more over the weekend. This second time I played it safe and filled the trailer about twice as much as the first go-round, hopefully insuring that I would have more than plenty.
Yesterday, I ran into a little snag in the assembly of the foundation when I realized I needed a massive slab of urbanite for underneath the door frame. Either that or I could spend some time attempting to level a couple of smaller, very uneven pieces. Forget that, I thought.
I went into Rutledge with four others, thinking we could heft an appropriately massive, flat slab I spotted earlier that day. Apparently not. It was hugely heavy. Instead, Brandon, a (very proactive!) visitor got Zimmermans Excavating (which was just down the road) to bring their backhoe and lift the piece into the pickup truck. We drove back to DR and to my warren, backed up to the spot in the foundation where the piece needed to be, and tipped the slab off the truck bed onto the ground, and then wiggled and walked the piece into its final resting place and then leveled it. That single piece of urbanite was probably three to four times the size of any other piece we had collected.
Later that day, Jeff and I stomped the first batch of earthen mortar (clay sand mortar) at a ratio of three buckets of sand to one clay. This we used to fill in the gaps (think cement mortar) between urbanite, along with gravel and smaller chunks of concrete. Today, we pretty much completed the first course and began stacking pieces for the second, final course.
I suspect this second course will be much trickier…
Two days ago, I went on a trip to collect urbanite (think broken up concrete from sidewalks and roadbeds) in a small town about twenty miles away. Thankfully, four willing folks offered their help in picking up the material. Urbanite is extremely heavy and you don’t want to move it more than you have to.
After an hour of collecting the concrete, we were physically exhausted. Unfortunately, we could not back up the pickup truck with trailer directly next to the huge pile — instead, it was about a twenty yard walk to the trailer, which made it that much more difficult. After unloading the urbanite at my work site, I was quite wiped out.
The next day, Jeff (my work exchanger) and I started assembling the concrete into the shape of the foundation wall, which is to be about 18″ thick. Working with the urbanite is almost like playing Tetris — you need to carefully find the right pieces to match up and fit together. Before starting, I thought I might have enough to finish the whole thing — boy, I was off. I didn’t even have enough to finish a single course:
So, it looks like I will have to make yet another exhausting trip.
Once the first course is laid out, I will make a clay/sand mortar at a ratio of four buckets of sand to one bucket of clay. This will fill the cracks between stones, preventing the entry of rodents, and blocking the passage of wind. Normally, one might use a cement mortar mix, but I am pretty opposed to using concrete in this building (unless it is recycled). (Fun fact: concrete is the second most consumed substance on earth, right behind water.) I hope the clay/sand mix will be sufficient.
If all goes well, I might start cobbing within a couple of weeks.
As I just mentioned, the digging and filling of the rubble trench is now completed.
Here’s a shot of the completed trench, pre-gravel. This photo was taken facing north. Take note of the drainage trench in the northwest corner. All of the topsoil is piled along the fence line on the east side.
Instead of simply piling all of the clay that was dug up from the trench in a big pile, I amassed as many five gallon buckets as I could to shovel the clay directly into them. In addition to buying a bunch (secondhand), I borrowed over 40 from other Dancing Rabbit members, making for a total of over 80 buckets full of clay. When it’s time to start cobbing, the clay will have to be slaked (soaked in water). So, putting the clay directly into these buckets has at least eliminated one step. (This won’t be enough clay for the whole building, though, so I’ll have to cart some from elsewhere in the village.)
The trench is about 18″ deep all around, and 18″ wide. No one has ever dug a trench this shallow before, so it’s a bit of an experiment to see if it’s truly necessary to go any deeper in this particular region. (Hopefully not. Generally, the ground does not freeze very deep here, I think.)
With the help of many hands, moving the gravel into the trench was no problem. We started with about an inch or two at the bottom, then laid down a 4″ perforated drain tile. On top of that tile, we piled more gravel up to about 2″ short of the top of the trench, tamping it at least twice during the process.
Oftentimes, I describe the shape of my cob house design to resemble a scotch tape dispenser. Here’s a view looking south to demonstrate that.
Next comes finding some urbanite, and building the foundation. I have at least one or two leads, but no guarantees on any actual material yet. Several of my inquiries into piles of urbanite have proved unfruitful thus far. Keeping my fingers crossed.
The past few days, I have been working long hours to dig the foundation trench for my eventual cob house. Today, it is complete, and ready to be filled with gravel. I am pretty psyched about that. The digging took four days with the help of Jeff, who will be work exchanging with me for a few weeks. The trench is approximately 18″ deep, and 18″ wide. It wasn’t nearly as difficult as I thought it would be. (That’s partly because I only dug 18″, not the 24″ or 32″ I was originally planning.)
As soon as I have a free minute, I will have to post some photos. Tomorrow, I will have the help of the first group of Dancing Rabbit visitors to fill in the trench with gravel. Very happy about that. Human power!
Over the weekend, I staked out my building site. I started by staking out the very center of the house, and then I positioned additional stakes to form the east-west and north-south axes. The house is oriented to take maximum advantage of solar gain. Using string, I was able to determine the slope of the site, which thankfully is not too-too dramatic. Then I drove a bunch of stakes in the ground at various other measured points as guides to create an outline of the shape of the house. I have pretty much committed the shape of the cob building to the ground at this point.
Last week was very rainy, but thankfully the past few days have been warm and dry. Since I am digging the foundation trench by hand, it is important to have very optimal soil conditions to dig. I started digging a drainage trench today (not part of the actual foundation trench, but a separate trench on the high side of the site to intercept rainwater), but the soil is still quite damp and difficult to move. The soil here has an incredibly high clay content which holds moisture for a long time. (All that clay is great for building, though!)
Unfortunately, it is supposed to rain again in another couple of days, so I won’t be able to get too far with the digging before I have to stop again. Tomorrow, I am having a huge dump truck full of gravel delivered to my site. Eventually, once the trench is completely dug (all two and a half feet of it), I will lay in 4″ drainpipe (or drain tile), fill it in with tamped gravel, and then begin work on my urbanite foundation.
It’s safe to say I’ve officially begun!
I need to start looking into getting some willing work exchangers this summer for help with constructing my cob cottage. Hopefully, with the assistance of a few work exchangers throughout this season, progress on the house will go much more quickly. Plus, it’s always more fun to work with other folks. Anyway, I’ve written up a rough draft for my “call for work exchangers” that will go on the Dancing Rabbit website sometime soon. Here it is:
– – – – –
Interested in learning about natural building? Looking to get some actual hands-on experience building a cob cottage? Want to experience community life in an off-the-grid, sustainable ecovillage?
I am looking to host work exchangers during summer 2008 during the months of May, June, July, and August to help with the construction of a small cob dwelling. The house is a spiral-shaped structure composed entirely of cob (a mix of sand, clay, and straw), complete with a reclaimed urbanite foundation and a living reciprocal roof. Cobbing is largely a hand-built process, with walls that are sculpted into shape by hand.
Other than gaining valuable natural building experience, you will have the opportunity to experience community life here at Dancing Rabbit — partake in community events and activities, eat seasonal and organic meals (largely vegetarian or vegan whole foods) in a food co-op with Dancing Rabbit members, and enjoy a beautiful summer in rural Missouri. As a temporary resident of the community, you will also be expected to partake in community responsibilities, such as weekly cook shifts and cleaning.
Prospective work exchangers should have some previous construction, natural building, or carpentry experience, although it is not mandatory. If you are responsible, have a strong work ethic, and are capable of regularly doing very physical work, you will be fit for this role. As a work exchanger, your cost of living here at Dancing Rabbit will be covered in exchange for 35-40 hours of labor per week. Non-building labor responsibilities will include cook shifts as part of a food co-op, and occasional cleaning shifts.
Host Offers
o Food: Full food stipend. You will be part of a vegetarian/vegan food co-op during your stay.
o Accommodations: Tenting space provided and shared facilities available for use (Common House with kitchen, showers, humanure system)
o Fees: Payment of all residency fees
o Transportation: No coverage provided
o Education and skills: Hands-on experience building a cob cottage, community lifestyle experience
You Provide
o Weekly hours for host: 35-40 hours per week
o Money/Fees/Food costs: None
o Other: strong work ethic, skill, responsibility, attention to detail, desire to learn, enthusiasm, and a good spirit. As a temporary resident of the community, you will partake in community responsibilities such as cooking and cleaning.
Contact Brian for more information!
Today, I’ve officially acquired my warren (read: space, plot of land). It was formerly leased by another member here who only gardened a couple of beds on the entire space, so the land is in very good shape. There are several garden beds at the north and south ends, and a single apple tree towards the back, as well.
The plot is longer than it is wide, with a maximum width of about fifty feet at the center, tapering to something like twenty feet up front. There is a very slight slope towards the north in the rear. I think that the entire space is something like 2,500 square feet. (Fun fact: this is roughly equivalent to the average size of the American house.)
I am very excited to finally have my own land, but of course it’s been very rainy and wet lately, preventing me from doing just about anything of purpose on the land. Rain is in the forecast for the next few days, so it might be a while before I can even start moving some of my lumber to the warren. We’ll see.
Can’t wait to start digging.
The days have been packed recently. A few days ago, I began cutting down pin oak trees for the living roof of my cob house. On Tuesday morning, Dan lent me a hand and we took down three trees in an hour and a half, despite the ground being quite muddy.
This morning, I went out alone and cut down a tricky tree more centrally located in a dense patch of pin oaks. It was very tough to bring down, since it was hung up in the tops of the trees. I walked back to the village, and thankfully Liat offered some help, and together we shook and pulled and dragged the tree down. This afternoon, I cut a smaller tree and easily toppled it. That leaves me with five total trees thus far. Hopefully I will be able to get at least two rafter poles from each. I need between twelve and sixteen of them.
The patch of land that I have been doing the cutting is very dense with pin oaks. Some are growing mere inches from one another. Pin oaks are tall and straight, making them appropriate for the reciprocal roof I want to build. The toughest part of the job is not so much the cutting, but the toppling of the trees, since they are so tangled with their neighbor trees. All of the cutting has been done with a bow saw, a hatchet, and a smaller saw for branches. It has been gratifying work.
Unfortunately, I don’t yet have a plot of land for my house. I have been in talks with another member here who is interested in letting go of his warren, since he has determined that it’s not worth the cost to him for the small amount of gardening he does on it. So there is that possibility. Because it’s not definite, I have not bothered with transporting the trees back to the village. (A damp ground doesn’t really help with that, either, though, which is probably the real reason I haven’t carted them back.)
We shall see.
Hi there, I’m Ziggy. In 2008, I launched The Year of Mud while building my first natural home. This blog is a collection of personal stories and experiences building with clay, straw, and wood over the past 15+ years. A few of the things that get me fired up are natural plasters, timber framing, & Japanese architecture. Since 2012, we’ve been hosting Natural Building Workshops so you can learn essential skills to build your own natural home.
