Monthly Archives

May 2008

Latest cob house pictures

By Cob Building

Ok, I think I was wrong about the 12-16″ of cob on the walls… it actually is a little more than that, it seems! Check it out:

house00

Here’s the lovely 5’x4.5′ south plate glass, with work exchanger Adam proudly displaying the setup. I was nervous about sticking that large a piece of glass on the cob, but the bracing is quite stable.

southglass-viola

This door buck was constructed using reclaimed 2″x6″ lumber from a deck that was demolished.

This here is the exit for the rocket stove flue on the south side of the building, made using some chunks of concrete. It’s about 10″ wide, so the flue should have about 4″ of play. Eventually this gap will be cobbed in once the flue pipe is in.

Electricity! Well, I don’t plan on having a power system, but I figured I should at least add in a switch box and one outlet (plus one exterior outlet) just in case…

First windows in cob wall

By Cob Building

The past several days (or week) have been busy, quite busy, in fact. I feel like I’m just now catching my breath. I missed taking photos for a few days for whatever reason, but I was sure to snap some today of the progress on my cob house, of which there has been much lately. There is an average of about a foot of cob all around the perimeter of the building, and the first window just went in this afternoon. We created a brace for a large glass plate, approximately five feet wide by four and half feet tall. This we stuck in the south wall (for purposes of passive solar.)

Over the weekend, we created a door buck and stuck it on the foundation, bracing it to be stable. Tomorrow, I expect we’ll get a second window frame made and stuck in the wall as well. Things are going fast! Today was incredibly productive with the help of nine visitors, making for a total of about eleven folks working all at once on cob stomping and applying. It was hectic to keep up with everyone, but it went smoothly.

Other happenings include getting an electrical switch box installed in the cob, along with a single interior outlet, and one exterior outlet. Thanks to Ted here for rigging up the wiring and getting it set up so that I could cob it in place. (I don’t have plans to install a power system, but I wanted to at least have something in place so there is that option down the road…)

Pictures coming soon.

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.

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

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!

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.

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!

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…

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.