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May 21
Love0

Rates of cobbing

By Cob Building

Lately, I have been trying to estimate how long it will take to build the cob walls of my cottage. I haven’t been doing anything very scientific to make my guess, just figuring a number based on the number of batches stomped for Ironweed kitchen (another cob/straw bale structure here at Dancing Rabbit), which took something like 150 total batches (some of which were undoubtedly doubles, however.)

Anyway, the rough estimate I’ve decided on is about 100 batches stomped by foot (rounding up to play it safe), completed in about a month at an average rate of four batches mixed and applied per day. (One batch is equal to three buckets of sand, and two and a half clay.)

Today, we stomped a whopping nine batches. I had the help of three others throughout the day, so we were able to do a lot of work. We also honed our technique to work more quickly – sometimes, it’s very easy to get caught up in finesse when it’s totally unnecessary. You can work quite quickly when the walls are still low to the ground. As they go up, however, it will undoubtedly slow down, what with installing windows, and shaping shelves and nooks and crannies.

Anyway, it’s been four days, and nineteen total batches of cob have been thrown on the wall. I am very happy about the great progress thus far.

May 20
Love0

Cobbing begins

By Cob Building

Yesterday, I mixed the first batches of cob with the help of my new work exchanger Adam and my friend Sara from New Roots in St. Louis. We made three total batches and applied them to the foundation, getting about 1/3 of the way around the building perimeter. It felt pretty amazing to be stomping those first batches for my very own cob home. It’s been less than a month since we started digging the trench.

Since the wall is so low to the ground right now, you can walk on the foundation and pack the cob by foot. Normally, you would use your hands or a cobbers thumb, but using your feet can be pretty effective, too.

Today, I got a dump truck full of sand delivered, which turned out to be a slightly traumatic experience. The truck got stuck in the road trying to back up into my warren. The roads here are very soft – they are pretty much just mulch on top of earth – not very good for heavy vehicle traffic. The driver was forced to dump the sand partly in the road, a good 25 yards from where I really wanted the material. I spent the morning moving all nine tons of the sand by wheelbarrow to my warren with the great help of very willing friends. I guess it could have been worse. But it was quite painful to see that dump truck tearing up the dirt road and making a bit of a mess.

But anyway, we got another four batches of cob onto the foundation this afternoon, nearly completing a single course around the foundation. I have a feeling the cobbing of the walls will go much faster than I originally anticipated. It feels great.

cobbingday-day02

May 15
Love0

Urbanite foundation (mostly) complete

By Foundation

The foundation is now mostly complete with the addition of a third course on the west side of the building. The past few days have been spent trying to piece together that topmost course with the remaining urbanite, and stuffing additional nooks with a clay/sand mortar. The construction of the foundation has gotten funkier over time since we used all the nice flat pieces at the start, and all that was left for the third course was the irregular stuff.

The mortar mix is kinda tricky to work with because of its high sand content (about 3:1); it’s very gritty and difficult to jam into tight spaces. I’m glad now that there are only a handful of cracks remaining. But it sure does feel great not using any nasty new cement mix!

mortar-claysand

On Monday, I hope to get a delivery of sand to begin cobbing the walls. Look out!

May 14
Love0

Cobbers thumbs

By Hand Tools

cobbersthumbs

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.

May 13
Love0

Continuing work on urbanite foundation

By Foundation

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!

May 06
Love0

First course of foundation complete

By Foundation

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…

May 02
Love0

Building the urbanite foundation

By Foundation

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.

Apr 24
Love0

Cob work site pictures

By Drainage Trench

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.

trench-complete

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.)

buckets

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.)

trench-detail

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.

trench-scotchtape

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.

Apr 22
Love0

Trench digging completed

By Drainage Trench

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!

Apr 15
Love0

Staking a site and digging a trench

By Drainage Trench

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!