Challenges and progress of building pizza oven on a slope

[Yokosuka dweller]

Now that the dome is soon closed off for good, I've started to look into inner/outer arch flue and that part of the build. I really like what JRPizza and Sharkey did which is this 's-shaped' flue design/serpentine and will probably try to see if I can emulate based on those builds. But I am not yet confident on the dimensions of the flue area.

My oven dome is around 32". For that I've read between 32-26" size that a 6" flue will work. Then I've also read that a flue exit into the chimney should be around 50 square inches. So that would mean I need to anticipate a 6" deep/8" wide end point of the serpentine, at least that would get me to 48 square inches, and just about enough. I haven't decided if a double wallet chimney is necessary or I can use single SS chimney. My father in law has single wall SS chimney lying around which I am welcome to use, but I am thinking that single walled carries a risk of cracking the chimney base due to heat expansion?

Another issue I need to figure out is the depth of the flue/entry area. Since my dome will be about 32", would it be enough if I used 4/3 firebrick? I would use 1/3rd as link to the inner arch with fire rope and refractory sealer cutting notches into the brick and placing those on top of the inner arch it like JRPizza did. If I did that, then it would give me 2/3rd bricks as middle area of the flue arch (about the planned 6 inches) to move upwards and turn into serpentine, and then a last 3rd - about 3 inches for the outer arch ring. Does this make sense, and would this be deep enough and strong enough to accommodate the chimney? Especially, would a 3 inch brick arch be strong enough? I can't see from the photos how large the brick pieces others have used were.

I may post this in another subforum as well since I'm not generating much traffic in here.

[JRPizza]

I can't remember if I posted all my dimensions, but the picture below shows how my aft vent arch bricks were effectively 3.5 "wide" with an additional 1" extension to overhang the oven arch, and although not shown my forward arch bricks were 3" wide. I don't know how much thinner you could go and still support the weight of the bricks that will go above the arch.

[Yokosuka dweller]

Thank you JR for sharing the diagram which I can understand. So you were using half brick width in aft arch which I'd do but that would mean 1,5" longer vent area. I'm not sure yet, whether I am going to go for 3" there or increase to 4,5 with the overhang on the inner arch. But I think I will go with the 3" forward arch just to keep the entry area relatively short. That would also be the most economical in terms of using 1/3rd bricks I guess, but the other day I went up into the backyard and managed to find another 10 really old SK32 firebricks which my wife's grandfather had used for something up there, way back when, so my brick budget has just increased and I'm grateful for that. Anyways, we have stormy and rainy (and snowy perhaps) weather here at the moment and the oven is covered and dry, so I won't be rushing ahead with this in any case.

[JRPizza]

Have you decided if you are going to build in a heat break? I think they are a good idea, but many ovens have been built without them. If you don't incorporate one, you can brace your aft vent arch on top of your inner arch and gain some strength, potentially allowing for narrower bricks. I didn't want to do that and wanted to keep the landing short(ish), so used the overhang to give some additional strength and fore/aft stability to that portion of the arch. You have a bit of inner arch projecting from your dome, so you might be able to increase the amount of overhang if you chose to decrease the width of the lower portion of the bricks.

[JRPizza]

The other thing you should do before you proceed is figure out if you are going to use the adapter plate that is meant for the type of pipe you choose (assuming you are using a metal chimney pipe). The dimensions of the plate will help you figure out how to transition from the opening in your vent arch to the pipe. I was able to find dimensions of my adapter prior to buying it so I could do some preliminary sizing. You will be able to determine if you can use a standard adapter or if you need to do something custom such as casting a transition or doing some sheet metal work.

[Yokosuka dweller]

Thank you very much, these are indeed things I also need to take into consideration. I am planning for a heat break on the floor as well as around the inner arch. So your point is right, I need to dedicate enough additional brick to cover the overhang between the arches, like in the primitive sketch here. I think this is pretty much a copy from your build - which makes sense, since I keep returning to the build threads or your build, Utah's and Sharkey's to get info and inspirations for next steps.





As for chimney adapter plate - I haven't decided yet but you're right it would be helpful to decide this before building the vent area. I think optically a mason/brick chimney looks better than a SS pipe. But weight is a factor, as is stability. If for example, I do not mortar the outer arches onto the floor, then building a masonry chimney would make the thing pretty top heavy. We have earth quakes here semi-regularly, maybe the thing would topple over. Similar to the states, I think in Japan a 1000mm double walled pipe is around 200 USD, then one would have to add adapter plate and chimney top/hat to that budget, which would run it up to 4-500 USD. But yea, these are some considerations.

[Yokosuka dweller]

8th course finished. Still working with the indispensable tool. But it's taking time to place the bricks now, partly because the mortar needs to set around each brick for a few minutes before I dare to remove the tool, and also - I decided to tailor-cut each brick to reduce or eliminate mortar gaps. This means I can only mix small batches of mortar. But since this is a hobby and not a job I'm enjoying it even it's a bit slow.

I think I may have only 1 or max two courses left before plugging this thing. Have to start thinking about what shape of plug makes sense, and how I would place it.

[Yokosuka dweller]

9th course now set. I could either mortar two bricks together and cut a larger plug now or tailor another course of small bricks with a smaller plug. I removed the IT, which has been essential really, and while the 9th course was difficult and bricks succumbed to gravity 3 times, I finally managed. It's not entirely symmetric, due to my cuts and my desire to use as many leftover bricks as possible to minimize waste. I also notice two flaws in this 9th course - namely that I have two instances where seams overlap. I couldn't see from the inside when placing them, so that's why it happened. But I gather that this is so close to the top of the dome that any crack cannot go vey far until it meets a juncture. So should be no issue.

Next I will do as others have done and recommended which is to scribe the outline of this remaining hole onto a piece of cardboard, and then divide into sections for bricks, as well as a round plug in the middle.

My idea is to cut those pieces from sleepers/horizontal brick pieces. That way I will have an inner plug that's too thin but which maybe easier to fiddle and fit into the confined space. Then, once that has set, my idea is to take as many remaining larger brick wedges / leftovers and place them on the top and then pour a very liquid homebrew mix over it and allow to set. But first need to see the scribed outline and see how difficult it will be to grind the last weird shapes.

[Yokosuka dweller]

Weather was nice this weekend so managed to cut and lay the last course and grind a plug. I didn't have a jack-lift and didnt want to buy a yogaball or a load of sand to fill into the oven so I devised another system, which I think can be my contribution to this community. I used a long nut and created a support system wherein the last course would be held up sitting on a circular piece of wood below, but which was held up with a lift system from the top. I then created two circular pieces of wood to ensure the last course would accommodate the funnel-shaped plug. It worked surprisingly well actually.

[Yokosuka dweller]

And some more pics here - including from the finished dome with the wooden floor brick removed. Feels real good to be through this stage of the build. But when I look into the oven I remember each crooked brick.

[terratree]

Great idea !!

This would allow a fairly quick course, I imagine ?

Nice work.

[JRPizza]

Congrats on closing out your dome! Novel use of a "gear puller" design

[Yokosuka dweller]

Hi Terratree and JR,

Thanks, yes it did work pretty easily to lay the last course and center stone fits very flush. One issue I have is that the last course is about 3mms too deep into the dome. It means if you're using this technique to assist the last course(s), you need to cut the bottom circular support plate at the exact diameter to ensure the smooth height/depth transition between the courses. I guess my support plate was a little bit too big and didn't push up the last course enough. But whatever, it works and looks kinda cool I think.

Now I am stuck thinking what to do about chimney. I wanted to go with a SS chimney, but here in Japan no stove/chimney stores carry anchor plates. Mason work is rare here due to earthquakes, so I guess there is little demand for anchor plates. Alternatively could do a brick chimney but I was planning to copy JRPIZZA's approach and if doing a brick chimney it would need much more buttressing. So, still in planning phase on next steps.

[modified9v]

Yes, congrats on getting that dome closed. Sure feels good doesn’t it? Really like your ingenuity. I will be following along as you build the flue arch. Nice job!

[Yokosuka dweller]

Had the day off today, nobody home so could make some progress. Great. Cut the bricks for the flue and entry and just kept going and put them in their place. My TDC brick at the very front arch is one of the old heavy duty fire bricks I've found in the back yard. Some of them are nearly pearl white and give an almost musical sound when you hit them. They're beautiful.

One mistake I made was to line up the mortar joint between the bricks that become the 'serpentine'. Well, they're in now, and I'll just move on. See if maybe I can interlock the next bricks somehow..