Intro: Brick Oven
For this Instructable, I have decided to go through a project that I completed a couple of years ago. I designed and built a brick oven in my back yard through a lot of hard work and several visits to the chiropractor. Most of the brick oven was hand built and this was due to two main reasons. First, my backyard has two levels which prohibit the use of any excavation equipment. The second reason is that I am not made of money. More time than money means that a lot of the things I want need to be handmade or modified. I also like to build stuff so it is not all bad.
If you are wondering where I got my plans to build the brick oven go to fornobravo.com. They have great kits for residential and commercial brick ovens. They also have free plans for you to build your own oven and a great community of brick oven enthusiasts that are more then willing to help you with issues.
After spending about 3 months on the site and deciding what I wanted to build and designing the oven, I faced the hardest part of the build, convincing the wife. This involved showing her that my brick laying skills did not totally suck by building a small brick wall between my upper and lower yard. As you can see, it worked. Your results may very...
Step 1: Building Permits and Foundation
First thing you need when doing a project like this is a building permit. This is important! Without a building permit, the city can ask you nicely to dismantle your oven and start over. In my case, when getting the building permit, the city had never issued a permit for a brick oven. They had just issued a permit for an outdoor fireplace. Close enough of a match that I the same requirements when building my oven, yay.
Here are pictures of my foundation. I am built an oven that has a base measuring 5 feet by 6 feet. Because I live in a fairly northern area, Northern Illinois, I needed a hefty foundation. I hand dug a foundation that is 1 foot deep into the top soil and an additional 3 feet into the clay. Each of the trenches is a foot wide. Additionally, there is an 8 inch deep, rebar reinforced slab that will hold the oven. Lots of work and at least one visit to the chiropractor.
Step 2: Pouring the Slab
After pouring the slab and getting an inspection (building permit remember?), it was time to pour the slab. Based on my calculations, I had to hand mix almost 3 cubic yards of cement. Nope, time to call a cement truck. Three cubic yards, while a lot to me, is a really small order to a cement company. Then there was the issue of my two layer yard. I decided to build a ramp to dump the cement into the foundation. This actually worked really well. It took 23 trips with a wheelbarrow to move the cement from the street to the back yard. Oh yeah one more thing about cement trucks, they charge you for every five minutes over 20 minutes for delivery. This added an extra $20-40 dollars for delivery and gave me a work out but it was better then mixing by hand.
Once you have poured your foundation, smooth off the top and let it sit for a week. This will allow time for the cement to cure and you to recover. You can then remove the forms and move to the next step.
Step 3: Supporting Walls/base
For this step, I build the base of the oven. This involved approximately 90 cinderblocks arranged in a "U" shape. The center section will stored the firewood and keep it dry. The number of courses needed will be determined by your finished height. In my case, I had to bring up the level to my deck and then add about 30 inches. A good set of plans will make these decisions much easier. Anyway, I dry stacked the cinder blocks. Made sure that they were at the height I wanted and then used "Quikwall" by Quikcrete instead of mortar. This is cement with fiberglass fibers used to tied all the the cinder blocks into a cohesive whole. I also figured that with the brick oven on top it was unlikely to move even without the mortar.
Step 4: Oven Slab
Once the base has been completed, it is time to move on to the slab that will support the actual brick oven. I started with some 2 by 12 boards cut so that I could make a form around the top of the base. This form would allow me to pour an 8 inch, rebar reinforced, slab that would support the rest of the oven. I also used cement board as the base of the slab. Cement board is used to back tile installations where there is the likelihood that water will be involved.
Here are the layers for the slab.
- 2x4's used to support the 3/4 inch plywood.
- 3/4 inch plywood to support the cement board. The plywood needs to fit inside the walls of the base.
- Cement board, these boards need to go all the way to the outside of the walls. Otherwise, you will be filling the walls of the base with concrete before filling the slab. Use duct tap to seal the gap between cement board.
- Rebar is placed every 8 inches. Mine is supported, temporarily, by some extra bricks.
- The form is placed around the outside of the walls. One tip, drive nails all the way through the form about 8 inches from the top. This will support the form and be fairly easy to remove once the slab has set.
Once your form is setup, find your brother-in-law (thanks Vic), and mix the 27 bags of concrete that will be used for the slab. Pour your slab and you are done for the day.
You might have noticed the missing rectangle in the top of the slab, this is for the "insulating concrete" that will be under the brick oven floor. "Insulating concrete" is a mixture of vermiculite and cement, 2 parts vermiculite to 1 part cement. We want this insulating layer so that we don't waste time heating the whole slab when using the oven.
Step 5: Brick Oven Floor
Now we get to the part where we actually start building the oven. For the building of the oven floor we use fire bricks laid on a thin layer of sand. As you can see, I have laid the brick in a herringbone pattern. Where the brick extend beyond the edge of the brick dome, I used a tile saw to trim them to shape. The bricks are not mortared to the slab so that, if need be, I can pull up and replace any brick that becomes damaged over the years.
One word of note, only use fire bricks when building the actual oven part of the brick oven. Other bricks are not made to handle the 850-900 degree heat and all of your hard work will not last for long.
Once you have placed the floor of the oven, it is time to move on to the walls.
Step 6: Oven Walls - First Layer
For the first layer of bricks, I choose to stand the bricks on end. You can choose to cut the bricks in half and then build up the layer, it is your choice. On the floor of the oven, I used a pencil and drew the placement of the bricks. I then dry fit the bricks. If you are wondering, the inside diameter of the oven is 36 inches. Once I was happy with the placement of all of the bricks, I mortared the bricks in place using firebrick mortar. The joints are around 1/4 inch, with the bricks almost touching on the inside of the oven.
Step 7: Oven Walls - Dome
Once I started the second layer, the tile saw paid for itself. Each of the layers consists of half bricks that are angled inward at a slight angle. I initially used wedges to hold the angle of each brick but soon found that this was not necessary. When placing a brick, try not to line up seams between bricks. This will create a line of instability that will be prone to fracture. Think of the bricks as being similar legos, when you build a wall, you want to stagger the joints so that your wall is strong.
The opening of the oven is important in both size and shape. There is no opening in the top of the oven so the air used to fuel the fire and the exhaust from the fire use the same opening. The correct proportion for this opening is that the door needs to be 2/3rds the height of the dome height. So, if your oven height is 12 inches the door height should be 8 inches. Once the oven door size is determined, your can build your door. To get the arch for the door, I used a form that I built. Just outside the oven door, I have a chimney that will move the smoke from the fire up and away.
So for each of the layers of the oven, I cut the bricks in half, staggered the joints, and slowly moved toward the top of the oven. For the last couple of layers, I used a leftover board, some bricks and sand to create a form. This allowed me to place the last couple of layers without the bricks falling into the oven. I am sure that there are people that can do this portion without using the form, I am not that person. If I were to do it again, I would remove the form sooner and clean the sand from the top of the oven. No one sees it but I know that it is there.
Step 8: Oven Chimney
Here are some more shots of the chimney. Using fire brick and mortar for the lining. Not much else interesting to say.
Step 9: Insulating the Oven
As you can see from the pictures, I have finished the dome of the oven and now need to insulate it. I had two options: insulating concrete or a rock wool blanket. One was cheap and the other was not, can you guess which one I chose? So I mixed cement and vermiculite as mentioned earlier in this Instructable and applied a 4 inch layer to the sides and a 6 inch layer to the top.
Side note: cement is used to create concrete (cement and aggregate). I used concrete for the foundation and oven slab. I used cement to make the insulating concrete.
The insulating concrete is kind of a pain to work with as it does not stick that well to itself. Once completed though, it is fairly sturdy. On top of the insulating concrete I applied a layer of Quikwall to water proof the oven.
Step 10: Finishing the Oven
The facade for the oven was created using bricks that I pulled up from an old patio the previous owner of my house had built. These bricks do not have to be fire rated so just about anything will do. The better your brick laying skills, the better it will look. I wish I was better. Since the oven is complete, you can now start the curing fires. There is a progression of fires needed to cure the oven while not damaging it. I would suggest no more then one fire per day. Fornobravo.com has a full schedule that you can follow when curing your oven. My schedule was the following:
- Small fire with just a little bit of kindling. No medium or large logs. Let the oven cool before progressing to the next fire.
- Another small fire with one or two small pieces of wood.
- Medium size fire with 3-4 medium pieces of wood.
- Large fire as shown in the picture.
- Use as desired.
For my oven, I use a combination of birch and oak. Birch burns hot and fast. Oak sustains a fire while providing a fair amount of heat. It takes about 2.5 hours for the oven to heat pizza temperature, once I start the fire. I can tell that the oven is ready because all of the soot from the initial part of the fire has burned off the inside of the oven. Once the oven is at temp, I push the all of the coals to the edge of the oven. I then wait 10-15 minutes for the floor of the oven to cool slightly and start cooking pizzas. If I am cooking lots of pizzas, I add an additional log or two on top of the coals for some additional heat. If you are wondering, it takes about 1.5-2 minutes for a pizza to cook.
Step 11: Finishing the Oven - Again
So the oven was completed and we used it a lot for the first year. One thing that I noticed was that I kept getting cracks in the outside shell of the oven. This was not good as it let water into the oven. Water takes a lot of wood and time to heat up and burn off. After dealing with this for over a year, I decided to modify the oven. I build some walls and a roof using steel studs with concrete board sheathing the walls and plywood for the roof. I spent some time finishing it so that the new matched the old. I now have a water tight oven that is a joy to use.
Please let me know if you have any questions.
Time to build: 100-200 hours
Weight: about 20,000 pounds
Chiropractor visits: 5-10
Use: during the summer about twice per month
Coldest use: December, in the snow
Largest number of pizzas: 20, cub scout party
What can you cook: anything that you can do in an oven. If you don't need the oven at 900 degrees, heat it up and let it cool before starting to cook.