Once the base was done it was time to start building the first oven. At this point I had to decide what to make the oven floor out of. I looked at all of the options and found out there was more than I thought. The oldest ovens had cob, stone and clay brick floors. Some of the more modern ovens had primarily fire brick, formed clay or metal floors. So I had to decide what you use for the floor. I knew the solid fired clay was out since I didn’t have a kiln and was way to expensive. The metal floor was out because I didn’t have that much and I wasn’t sure how long it would last or how well it would hold the heat. So that left me with fire brick, brick and cob. I seriously thought about using cob but, all of the information that I could find said that it took a lot of maintenance and repair.
So I decided on brick but, I wasn’t sure what kind to use. Again I started researching and I was really surprised at what I found. The vast majority of people, companies, researchers and experts recommend using fire brick. What they don’t tell you is how much energy goes into making the fire bricks. The fire bricks require specific mineral mixes to make and those minerals all require mining. Then they have to be pressed by machine into shape and finally fired at extremely high temperatures. This process uses an incredible amount of energy and releases a large quantity of CO2 per brick. The clay brick by comparison is a mix of clay and sand put in a form to set, then removed to air dry and finally fired. The firing temperature for the clay brick is much lower than the fire brick.
Well I liked the option of the lower CO2 emissions from the red brick but, everyone I found says use the fire brick because the red brick isn’t as good and won’t last. Then I looked up clay brick ovens and I was amazed. I found restaurant ovens that have been in constant use in some cases for over 100 years here in the US. I found all kinds of information on brick ovens in Europe that have been in constant use for over 300 years. I also found a ton of sites detailing ovens between 50 to 80 years old.
So after looking at all this I couldn’t fathom why so many people were trying to sell everyone on fire brick. Even many of the green building sites recommend them. I figured if the clay brick lasts even 50 years then it would be well worth it. So at this point I had decided about 80% that I would use the clay brick.
My next step was to find the bricks. Since cost is a factor in this project I wanted to try and find some reclaimed bricks to use, preferably free or really cheap. My efforts were a bust. Several times I thought I had found free bricks but, they were always gone before I could get them. After a series of disappointments I gave up and went to the local Home Depot. OK I know I wanted to do this without spending much if any money but, it had been several weeks since the base was completed and I really wanted to move this project along. So I looked around and found the bricks. I found the three types of bricks I could use were the new clay brick, the used clay brick and the fire brick. Well the fire brick was $2.15 a brick so forget it it was too expensive. What I couldn’t understand was why the used clay brick was $0.52 per brick and the new clay brick was $0.43 per brick. So I opted for the new clay bricks.
OK I need to take a step back and let you know how I figured out the number of bricks that was needed. I know your eyes just rolled back into your head while saying not math! Alas yes math is required but, it really isn’t hard at all. In my case the internal oven was planned on being 48 inches in diameter. That would be a 24 inches radius. Yes I know another fancy term but, the radius is just the measurement from the center of the circle to the outside or half of the diameter. We figure out the number of bricks needed by figuring out the area of the brick and the area of the circle.
