In 2015 we built a purpose designed cob shed for storing our apiary boxes off the hives over the winter. We have taken to calling this the Honey House since it resides in our bee yard and holds apiary wares. It is just under 90 square feet in area, with an interior height of roughly 8 feet. It has a floating broken concrete foundation, a sealed earthen floor, and a green roof strawberry garden. We learned a lot from building this and had a lot of fun while we were at it. Below is a photoblog of its construction. Please be warned, we are NOT engineers, nor are we experts in cob or construction. We can not guarantee the safety of this structure and while we feel safe using it, we assume no responsibility for structures built based on its design. We hope you feel inspired by what we build but PLEASE do your own research if you are endeavouring to build a cob structure to ensure that you do it safely. We have several great references listed throughout this site.
As always, our foundation started with a gravel filled trench. The size and shape of this structure was designed to fit a rather awkward space between a grove of trees and single, volunteer, young sitka spruce that the family did no want cut down. We also wanted something relatively shallow to reduce the risk of things getting lost forever in the back of a deep shed. This foundation was dug in the middle of winter when the ground was frozen. It was terrible work but allowed us to better gauge our local frost line. As it turns out, our frost line is extremely shallow however, we still dug our trench to be roughly 16 inches deep. The trench was filled with pea gravel that was dug out from under an old rotting duck shelter that we tore up on what is now the new greenhouse construction site. From the photos you can see that everything ended up getting frozen together.
Next came the concrete and rubble foundation, just like the garden wall. Also, just like the garden wall, this was a finicky job. So much in fact that when we came across a bunch of reclaimed cinder blocks from a torn down warehouse, we took them and built part of the foundation with them. What a mathematical dream! We used them upright and filled the holes with clear crush gravel. We resorted to pouring some concrete for this project. Not much, just a strip along the front for the base of the doors. We could have done this without concrete but we were out voted by the family, who still don’t have full confidence in fully earthen building. The rebar stake mid span will be the mount for the vertical support post later. Then we started cobbing. So far, so good.
We knew we wanted to put windows in this shed, partly to let light in, partly because we thought they would look nice, but mostly so we could practice installing glass in to cob. We found two large matching glass panes in an alley. They had been taken out of a an old entertainment cabinet and they were the perfect size, we decided. When we got to a height that felt right, we stopped laying down cob where the windows would eventually go. Cobbing takes foresight and sometimes we are lucky enough to have some.
Cobbing is tiring work! Jonah is taking a well earned break in this photo. He built a lot of this honey house with us. Once we got to a height that would accommodate the glass window panes, the lintels for the windows went in. We found these fantastic GluLam timbers in a dumpster outside a construction site. It’s amazing what people will throw away! We set them in to place and levelled them off. To help minimize the risk of slippage we nailed some offcuts at perpendicular angles to the ends of the timbers, to give the cob something to lock around. You can see these in the second photo, below. Two timbers were used per lintel, side by side, with a small gap between them that the glass could slide in to later. Some cobbing books recommend that lintels be mounted on to wood mounts resting on the cob to prevent the cob from getting compressed. We felt that our cob had locked up sufficiently to easily carry the weight of the lintels so we left the wood supports out.
Then we kept cobbing to get to a height that felt right. Just keep cobbing. The wall started to get a little blobby. We paid dearly for that laziness later when it came time to shave.
Then it was time to install the front wooden supports to enclose the structure. We used one of the GluLam beams as a centre support post and spanned a long 4x6″ timber, that we were lucky to acquire from a friend, across the front such that it rested at its midpoint on the vertical post and at its ends on the cob walls. Getting that beam up was ridiculously difficult! We lacked the foresight to recruit help with it. Below is a photo of the beam half way up with Ryan looking exhausted and haggered next to it. We used the ladder to, sort of ,”walk” it up to height. We used a plumb-bob to align it with the rebar post in the concrete over which we mounted the vertical post by way of a hole drilled in to the bottom of it. Once everything was sitting nicely we cobbed the horizontal beam in to place at its ends and secured it to the vertical post with screws.
Next came the time to true up the walls that had become slumpy with height. We shaved the blobby parts and built up the low parts. There were lots of both. We used “poo plaster” to fill in the low spots. This is basically a sloppy wet cob with lots of horse manure mixed in to make it stick. In the first photo you can see the excess cob coming off. The second shows the poo plaster being built up.
The windows just popped right in to the gap we left between the lintel timbers. Once they were seated nicely we cobbed them in. EZPZ.
On the outside we made some window sills and cobbed those in to place too.
Then the roof trusses went it. We worked the details of these trusses out in, you guessed it, Google Sketchup. (This is not a paid advertisement for Sketchup, I just happen to use it all the time). We used 2x6’s for this and extended the eaves out with 2x4 supports. I wish we had used 2x10’s for the trusses. Maybe then I wouldn’t have so many nightmares about this thing collapsing. We bird’s mouthed them a little to make sure they sat nicely. They are spaced 16″ on centre. I wish we had done 12″. Nightmares. Once they were placed nicely, they were cobbed in. And from here we went on to building the green roof. See the next post for details on how we did this.