Breaking Ground

Well hopefully at this point you will have taken the time to make all of your choices and decisions as to the size and locations of things. As well as the materials that you wish to use and their locations. Once these things are done and you have your plan in hand along with your trusty tape measure you're ready to break ground.

OK when I say breaking ground what I'm talking about is grabbing a shovel and digging. I know that sounds like work. No really, when you choose your size and location you will have to have some sort of foundation. If you are building in a wet or rainy area then you will need good drainage. A rubble trench would work well in that situation. That means you have to dig a trench about 12 inches deep and slightly wider than your support walls. You then fill in the trench with gravel and begin laying your first coarse of your support walls on the gravel. If you're building in a dryer climate than you only need to dig a shallow trench and lay your first coarse in that. The truth is that even if you were to build your base on flat ground with no trench and make it solid then it would be so heavy it would be very unlikely to ever move but, the foundation makes for a much longer and more stable life.

OK so now on with the show. I started with a shallow trench, about 6 inches deep and laid the first coarse of urbanite. I then mixed up a thick clay mud and sand mix to use as mortar. I then began laying the progressive courses and mortaring them into place with the mud mortar. Now I had to keep in mind that the finished height of the support walls needs to be about 7 inches less than the final height of the floor of the oven. We built the support walls in one work day. We waited for a day to allow the mortar to set and begin to dry. Then we began to fill the internal voids with the dug up soil. We would fill about 10 inches then tamp it down and repeat the process until the voids were filled. After the voids were filled I used the hose and applied some water to harden the tamped earth. This worked extremely well. Then we let it dry and cure for several days.

A word of advice for those with helpers like myself. Be careful when everything is lined up to start with. I say this because some how when all was said and done our base was suddenly very out of round. I still don't know how it happened but, I knew I had to find a way to fix it. Enter the cob. We began learning how to mix and what the right consistency was for the cob. This comes down to simple things. The cob should not be too wet. This is important, cob can't be overworked but, it can be under worked. Under worked cob is coarse and doesn't stick or blend well when placed. To place the cob start with the cob rolled into balls so it's easy to handle and push, rub and smack it into place to get the shape you need on your base.

So we struck out filling in and smoothing out the odd shapes to create a fairly round oven base and counter. Since we didn't want one section showing stone and another showing cob so we covered the entire base with cob. Note of importance here is to know that you can only add one or two layers of cob at a time. If you try to add too much too fast it will fall off. You have to add a layer and let it set before you add a second layer. So it took us about two weeks to cob the outside of the base. This was definitely a learning curve for us so be prepared but, don't get discouraged. Once any cobbing is completed give the base a few days to cure and dry. Also remember to use the clay slip when the layers have dried to wet the under layer and act as a bonding agent between the layers.

Once the base is dried mix up a batch of cob and make sure the balls are more than 3 inches in diameter. Then place the balls all around the perimeter of the round portion of the base. Then use a level when working the cob balls down to 3 inches. Let this dry for at least another day. Now fill the top void with a medium grain sand and use a screed and level to smooth and level the sand. This will prepare your base for the oven floor. These are the same steps that I followed.

I do regret not having any pictures to show of this process as we built the base. I had some wonderful pictures of the process to the finished base of all of my kids working on it. Unfortunately I had not downloaded the pictures before my phone was stolen. I will begin including pictures as soon as I get to the point where I got a replacement phone and began taking pictures of the kids and the oven again.