Oregon 46" Neapolitan Wood Fired Oven Build

[CharlesPizzaiolo]

The oven is not completely finished, but I have finished the curing fires. So yesterday I cooked the very first pizza! Can't believe I can finally cook in the oven!

Thanks to everyone in the forums for all the advice!

I will post later on as I continue to work on the stucco and other aesthetic parts.

[CharlesPizzaiolo]

Next I installed the insulation. I have 1" thick ceramic fiber blanket (Inswool). From my last post you can see that the concrete cylinder at the top of the dome is about 6" tall. In order to smooth out the transition from the dome to the top of that cylinder, I put extra insulation on the top half of the dome. So I started put putting two layers of insulation on the top half of the dome. I then laid long strips of insulation that reached from the cylinder all the way down to the slab, i did two layers of this. So there are four layers at the top and two layers at the bottom of the dome. I found that by using long strips that reached from top to bottom, friction was able to hold the insulation in place and keep it from slipping.

To support the first layer of stucco, I am using lath for the vertical sides and chicken wire for the rest. I thought that the lath would be necessary for the vertical faces, and that the chicken wire would be fine for the more horizontal parts. The chicken wire is also nice because it is more flexible and is easiler to form to the shape of the dome. I suppose you could cut the lath into lots of thin strips, but think the chiciken wire will be just fine, I'll let you know on Monday if all goes well.

Getting the lath secured was kind of tricky, especially along the bottom edge. I ended up drilling a couple holes in the concrete and bricks of the door and using concrete screws. This worked well. Next oven I build, I'm going to think more about this in advance and maybe I can embed some wires in the dome concrete along to bottom edge or something...

[CharlesPizzaiolo]

My plan is to have the chimney sit at the very top of the dome. So I need a vent that goes from the opening in the door up to the top of the dome. I blocked off the door opening with styrofoam and created a sand mold. I put some wet newspaper on the sand and then applied a 1/2 to 1" thick layer of refractory concrete.

For the top of the dome, I built a form and poured a thin walled cylinder of concrete. A terra cotta chimney will sit on top of that. The vent going from the door opening connects to a hole in this cylinder.

So I've done a few curing fires now, and some smoke does exit through the door, though most seems to go out the chimney. There are two sharp corners that the smoke has to go around to get into the chimney and I think that rounding those out will help a little. I think that I could have made the vent a little larger and that would have helped. But overall I am happy; standing in front of the door while my curing fires were going, I wasnt getting a face full of hot smoke, so I know I'll be able to operate the oven just fine.

[CharlesPizzaiolo]

There's a few things going on in this next post.

In the last post, we didn't install the two dome pieces over the door. For these, I made a template out of styrofoam and then transferred that shape onto the concrete piece. Those pieces were light enough that I could manually set them in place.

Then I mixed up some refractory cement and poured it in the center of the dome, I'm calling this the cap stone. I put some wet sand in first to make a mold to match the shape of the inside of the dome. Then I covered it in some plastic to cure.

Last thing is I poured anchor blocks for my metal dome support band. This metal band goes around the perimeter and supports the dome. The band is anchored to two pieces of metal channel that are one either side of the door. These pieces of channel are embedded in concrete. This concrete is tied into the slab by two pieces of rebar.

[CharlesPizzaiolo]

The big day has arrived. Dome day.

We assembled the crane. Installed a stool to support the dome pieces at the center. Used some shims which we about 1/8" thick to set a mortar gap and to get the height at the center correct. We started by setting all eight pieces in place with shims and getting them all aligned. Then, one piece at a time, we removed every other piece, mortared both sides, then forced it back into place (with a lot of pounding with a rubber mallet).

Next post I'll show the final touches to the dome.

[CharlesPizzaiolo]

OK next step was the door. I build a wood frame to help form the arch. I decided to taper the entire doorway so its narrower at the back and wider at the front. I thought that would be a clever way to allow a door to fight snugly and would look cool, we'll see how well that works.

As you can see I have a LOT of mortar cleanup to do. I probably should have been more careful as I was laying the bricks but I'm a beginner at brick laying, so it is what it is. I don't yet know how best to clean up the faces of the bricks. I have some extra brick so I'll smear some mortar on them and then experiment with methods of cleaning them up.

I've installed a metal bar across the top that is bolted to two pieces of metal channel. The channel holds the sides of the door together so the weight of the arch doesn't push it apart. The channel is cemented into the slab. I also have a temporary version of this at the back of the door; later the dome pieces will support the back of the door.

[CharlesPizzaiolo]

I've gotten WAY behind on posting. I have actually fully assembled the dome. I'm going to try to catch up, posting one step at a time.

So earlier in this thread there was discussion about how to lift the large (about 120 lb) pre-cast dome pieces. My solution was to embed a piece of rebar as a lifting hook. There was concern that the rebar would cause cracking. So I did some experimenting...

I made 3 samples: a control (no rebar), one with rebar, and one with rebar wrapped in about 10 layers of plastic wrap. The idea of the plastic wrap is that it will create a small gap between the concrete and rebar that will allow the rebar to expand. I cured the pieces slowly just as I will the oven. I then took two propane torches (you only see one in the picture because I was holding the camera) and pointed them both at the base of the rebar. I held both torches there for 5 minutes. The rebar got red hot, but just in the area with the flame was touching. The point was to see if the rebar would expand and crack the test piece. For fun, I pointed a torch directly at the control piece, it looks pretty cool when you do that...

Anyways, there was no cracking of any kind either during curing or when heating the rebar. I think that this concrete is very strong and I think that the plastic wrap will work to create a gap and give room for the rebar to expand. The dome is assembled now so time will tell if I am right...

[CharlesPizzaiolo]

Bwhite Looks good! If I were to do it all again I would look into the solutions David and Chach are talking about. I will definitely do something to protect the steel from corrosion before the summer is over.

[Bwhite]

CharlesPizzaiolo Thanks I think it turned out nice. I did a 3.5in slab with angle iron across.

[Chach]

I did the angle iron thing but I put bond beam block on top and put rebar accross it and poured it monolithic with the cells and slab the steel was there just to hold the span now the concrete and rebar will take that over. you can do the same thing with a wood form instead of the angle iron amd let it set for 7 -10 days and then you can remove your form technically 28 days is better amd is the norm for structural items but your not supporting thay much in the span simce the rest of the slab os supported on all the other sides

[david s]

The conventional way of using lintel blocks/bond beams/knockouts which have a channel that can be filled with reo bar and concrete is neater, probably stronger and not subject to corrosion because the steel is not exposed.

[CharlesPizzaiolo]

Bwhite I cant quite remember now, I want to say 3/16 x 2 x 2. Here's a pretty good picture of it. I trimmed the cinderblocks that sit on top of the angle so that the angle sits flush with the cinderblocks. You can see me doing this in the video in post #4 on this thread.

[Bwhite]

CharlesPizzaiolo What width and thickness angle iron did you use? Is the front of it flush with the cinder block or does it stick out?

[david s]

The thermal expansion for the temperatures we fire to is around 1% or about 5 mm/m. You could double that if it were a kiln. So, the steel bracing just needs to be firm, hence the threaded adjustment. When the oven heats it becomes tighter.

[CharlesPizzaiolo]

So I've got a question. I'm building a low dome. Inner diameter is 46" and the inner height is 17". I've been thinking about how the dome is meant to support itself. With a high dome the curvature of the dome is the same from the top to the base, and as far as I understand the weight of the dome gets transferred mostly into compression (and I think some shear) between bricks and the surface the dome sits on. But with a low dome, usually you have vertical walls for the first course and then transition to a curve. The result is that the weight of the upper part of the dome pushes outward on the vertical section. I've found these two photos of ovens with a similar dome (one is a barrel oven but I think the idea is the same). And they both have added metal structure to resist this outward force. There's also a drawing of my dome with some dimensions. I've been going back and forth trying to figure out if I need to do this.

I was going to go ahead and add this support because, why not just overbuild it to be safe. But now I'm thinking about the thermal expansion of the dome. When the dome heats up it's going to expand, and this metal structure would try to resist that. Of course it would not be able to, so something is going to give way.

I'd love to hear some opinions on this. Thanks!