Building a Bread Oven
Start Date: August 20th, 2014. Getting a Start on the bake Oven. Footings in place and ready to set blocks.
August 22 – Man, is it hot! 97 today. 97 tomorrow. 97 Sunday BUT a cooling trend on Monday with a predicted high of 96. Here you see the first two courses of block in place. Soon we’ll backfill and start laying up the above-ground courses.
A decorative course will add some visual interest and bring the oven hearth height up to optimum working height, which, interestingly, is at the height of the baker’s heart. Get it?
Heart – hearth. Weird.
Now is the time to get excited. The form for the oven support slab is in place. It came out pretty level, even with our primitive methods. It remains to be braced.
We placed the concrete Oct. 7. This is the support slab for the oven. Notice the footings for the shelter posts.
Wade prepares a recycled fence post to become a support for the outdoor kitchen shelter.
Shelter frame in place.
The first truss goes up.
Forms and supports are off the support slab, and the metal is going on the roof. The black cubes are Foamglas, rigid high-temperature insulation.
The hearth slab form is in place with the Foamglas installed. The piece standing up shows the thickness – 4″, R~ 13.75. The brick dome and concrete cladding will go on top of the slab when it is poured.
The hearth slab was placed, and a row of hearth bricks dry fitted.
Working on the firebrick hearth. The mortar is a weak mix of 3 parts fine silica sand and 1 part potters clay.
Hearth bricks all in place – Nov. 23, 2014. Next comes the arch wall of soldier bricks, then the spring course, then we’ll pour the buttress which will hold it all in place.
Cutting bricks. It is now too cold to lay them, but the weather folks are promising a string of days and nights above freezing soon. The angle cuts are on bricks that will be the spring course. They sit atop the walls and begin the arch.
The spring course laid with the flue opening located. Notice I had to knock out a couple of bricks to get the flue in place. The bottom of the arch will be at the top of the flue opening. I first intended to use a 10-inch flue, but that would take up most of the rear wall. This is an 8-inch flue. The spring course enables the gaps on the outside of the arch to be much smaller than if the arch was started from the horizontal top of the wall.
The buttress forms in place. The space between the forms and the soldier course – about 4″ – will be filled with reinforced concrete. This will prevent the arch from forcing the walls outward and provide additional thermal mass.
We got a batch of concrete with no fines in it. It is strong enough to buttress the brick wall, but its thermal properties leave something to be desired. The Quikrete guy is working with us on a fix.
So, instead of working on the deck, we will be busting out and replacing concrete. I tried a test bust out today and the brickwork will not stand up to the removal process. On the other hand, there appears to be no bond between the bricks and the concrete so the bricks can be reused without much work. I think not only was this batch light on fines but also on Portland.
PS – I had a bag left over and did a test batch very wet. It was fine – a little weak but fine. The problem was I mixed too dry. So now I have to bust out the bad concrete (the bricks come with it) and redo everything but the hearth. I’m going to take this opportunity to modify the mortar recipe. The first stuff was too weak.
The brickwork redone and the new concrete in place, this is the inside of the arch support form.
The arch brickwork begun.
Close-up of the other side. (Hopefully, they meet in the middle.) The news paper keeps the mortar from penetrating into the holes in the masonite and bonding the form to the arch. In order for this system to work, once the arch has set up, the shims holding up the form will be removed (notice the yellow strings in the pic above), the form will drop down 1/2 inch and slide out the front of the oven.
Yay! The bond works out. I’m only able to work a day at a time because it often freezes at night. Hard on the mortar.
March 13 (Friday), 2015 – We had a warm spell, so I was able to finish the arch. Here you see it with the form removed and ready for cleanup.
Getting some warmish nights, so time to finish up the brickwork on the oven. By the way, the peach blossoms “seem” to have survived the frosts. We’ll have to see if they set any fruit.
The oven arch and the form for the concrete oven front. This is to tie it all together and provide thermal mass.
Framing for the oven enclosure. The framing is steel – not combustible. The enclosure will be filled with loose perlite, an expanded mineral insulation.
Most of the oven enclosure in place. The sides are cement board.
The oven is finished. I could add 5 more bags of perlite to the enclosure but I will wait on that to see if there is a commercial use for the oven. The perlite is very dusty.
I had this ready to use by harvest time and was able to process three batches of tomato sauce on the little wood stove in the back. It got just hot enough to simmer a full pot of sauce.
The small counter on the left is about to get a set of wheels that will let me move it where I need it.
The rest of the kitchen includes some prep space for the baker.
2022 Update – The flue exit piece had to be replaced and so the cementboard “container” that surrounds the oven had to be opened. Perlite is almost a liquid. It was difficult to contain/capture/handle. It’s a fine powder that irritates the lungs. Next time I will use ceramic blanket.