Here’s a little video showing off a gorgeously designed cob cottage interior by Meka in southern Oregon. Beautiful curves, built-in shelves and furniture, and a wild staircase design are the highlights.
Ok, so my original estimate of 100 total batches of cob to complete the walls may have been off.
Eighty plus batches later, the walls stand at an average height of 3.5′ (not including the foundation), which is probably half the total amount of cob necessary. Some taller spots are now no longer workable without standing on a bench (as seen in the areas next to the south window in the photo above.)
Now begins the time when the actual cob application slows down, due to the extra step of having to stand on and move a bench or scaffolding (which I might just need to make soon…) to work the walls.
We didn’t get nearly the same amount of work done this week thanks the absurd amount of rain, but I guess a little break is an okay thing, too…
I thought I might touch upon the actual cobbing process, since I haven’t really talked about that specific element of building very much. Over the past few weeks, we have developed a very efficient working system, allowing us to quickly stomp, loaf, and apply the cob to the walls.
It begins with a “burrito”, the final cob mix of sand, clay, and straw. (Once cob has reached its ideal mixed state, you can roll it and it keeps its shape, which is something like the shape of a burrito).
Once we are satisfied with the mix, we begin to make “cobs”, or little loafs of the material. It’s almost like kneading dough: grab a bunch of cob, and make a loaf that can easily be picked up without breaking. (Making each loaf should take no more than a few seconds.) We call the really big ones “wonderbreads”.
We then carry these loaves to the wall (which is typically no more than a few feet from where we are mixing), and line them all up. (First we soak down the walls with some water so this newest layer gets worked in to the existing cob more easily.)
Next we take cobbers thumbs and “stitch” the cobs together, making sure the straw gets worked well, and the individual cobs can no longer be distinguished. This newest layer should also get worked into the layer underneath. This is a quick and rough job that goes quickly. The main key is create a cohesive, monolithic wall.
Next, we work the wall with our hands, creating a clean, plumb edge. Viola!
Here are some different angles of the cob house in progress:
This is an extraordinarily rainy spring. We’ve had so much rainfall so frequently, with so many warnings of flash floods and tornadoes the past number of weeks that it’s been hindering not just our gardens, but local farmers from getting their crops in the ground, too. And of course it’s been washing away all the mulch on our roads here, and slowing down building. At least the cisterns are full.
Every day the past few weeks, it seems that there’s been a warning of severe thunderstorms — never just thunderstorms, always severe thunderstorms. Thankfully they don’t always occur as predicted, or I’m sure my cob walls would have washed away by now.
I write this after another night of rain. The cob walls are very wet and soft to the touch in some spots, and the sun is nowhere to be had, but very thankfully (and surprisingly), there is no rain in the forecast the next two days. I am quite tired of worrying about the weather by now, and I really hope this rain dies down sooner rather than later. There is certainly benefit to having a roof up before your cob walls are built (as this very rainy season shows us), but unfortunately, that wasn’t really an option for me. I’m beginning to wish it was, though!
The cob wall is growing day by day, despite tremendous recent rainstorms.
On Monday night, we suffered a huge storm, with 3.5″ of rain pouring down overnight, complete with blazing lightning and ground-shaking thunder. The following morning, a little flash flood passed through, dropping a whole additional inch of rain within a mere 20 minutes. The whole night and throughout the flood, I feared for the well-being of my house in progress, but the cob walls survived. The walls were covered in tarps (and not fantastically, might I add — there were many gaps/tears for water to enter), and the walls did get soaked, although there was nothing more than surface damage when all was said and done. The walls dried the next day, when the sun decided to come out.
Since that storm, I’ve been on an obsessive lookout for rain and trying to do a better job of tarping up the walls.
But anyway, progress has been brisk. Tom (a.k.a., Treetop), a friend from St. Louis came up on Tuesday night, and it’s been nice to have his extra help. Currently, the walls are sitting at a comfortable three feet in height most of the way around, perhaps even higher in some spots. We banged together and installed a window buck for a southeast-facing window at the beginning of the week, and yesterday, I starting cobbing the first shelf.
The make the shelf, I have been using “corbel cobs”, long, narrow, thin cobs packed with extra straw for tensile strength. These are laid on a level wall and then stitched together at the back, and pinched in the front. The first course hangs off the wall by about an inch, and the next corbel cob courses follow suit. A few more courses and the shelf will extend a good 6-7″ off the wall. This I intend to be a book shelf.
I estimate that the walls are about 1/3 of the way complete. The sand reserves are getting low, too — looks like I’ll need another nine ton delivery within a week or two!
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:
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.
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…
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.
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.
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.
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!
On Monday, I hope to get a delivery of sand to begin cobbing the walls. Look out!
About The Year of Mud
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.
