36" Pompeii in Indiana, US

[GreenViews]

Greg, Thank you for your comments and feedback. I've read many comments about lower dome being better for cooking top of pizza specifically, so I guess we shall see Glad to have another builder at same stage with similar design ideas . I also decided to save my older, slightly harder used firebrick for near the top of the dome which I will have better heat transfer characteristics, might also help. After some drawings, I decided to go up about 1/2" from the recommended low dome build from the FB ver2 guide, mostly for IT stick reasons.

If you go back in my thread, you can see drawings I did to think through IT stick placement and the idea of just shortening each course. One problems was the brick face angle difference while indistinguishable at 0 and 90 degrees became a bit pronounced half way up the dome (45 degrees). That would change the physics between the courses in the event of mortar failure. Does it matter? good question. But I suppose an angle correction step could be added to the IT by way of a simple shim or with an angle adjustment on head of IT which might be hard to make in a sturdy fashion.

I figured if I were to just shorten IT, rather than fancy calculations (which I have skills to do) It would be more practical to just create a single plywood template of your exact desired dome arch minus 1/5" off bottom. Then cut it in thirds for later removal, reassemble and place inside your oven to one side of your IT which you could raise at the beginning of each new course on the back side of oven right next to IT to get proper IT adjustment for the new course in regards to cut and face angles. One could even create a number of lines on this wood arch template with lines toward true arch center. So I guess that would be a hybrid between forming and creating IT. As I write this, I'm now considering doing just this with height and angle adjustment each course rather than keeping part of my floor and sub-floor out during build!!! I like this solution better than a dual angle IT which I have also seen, but seems more complex adjustments.

The vent posting: They used auto breather vents. here is one location discussed: https://community.fornobravo.com/for...ii-build/page4

Other Low dome thoughts: I think I'll add at least small amount of pcrete buttressing even without a full soldier course which I decided against so as to not create an even wider (lower focal center) arch. The guy who did a large commercial lower dome oven (don't remember name at moment) has some serious pcrete buttressing with rebar, but that was a massive oven and massive span with full brick in arch. Amazing, but not what we are doing, lol. Interesting idea on the sand form inside. I'm going to try and build without supports and see how it goes. Time will tell if I change my mind, but I also have a bunch of Styrofoam here I could use if need to add later on top of a high platform inside oven.

My floor seems quite hard this morning, very different from yesterday. I'll test better when I get to work in earnest, but It is hard enough I am quite confident in keeping it below the floor/subfloor. Worst case is that around the dome outer 2 inches I could possible remove some and put new with higher ratio of refractory. I even have a little refractory castable I could use. This layer could be either insulating or non-insulating as I have insulation outside of this layer, so I think going with strength is better option for me here since I don't want to always worry about dome collapse or weakening because of my failure on this step. This is only a 3/4" layer, so burning through a little of the safe, but expensive product like the refractory castable for the outside 2" to ensure good dome support isn't going to break the bank for me. Does make me wish I had known my CaSi board would come in such a cracked, less than perfect state. I probably would have used half the width and just planned on a normal pcrete layer in addition but underneath it maybe. Or maybe I'm worrying too much about the CaSi strength. Not sure. I know I couldn't load all the bricks for my build on my little trailer that I use for 3/4 tonne hauling fairly regularly. A lot of weight in the dome!

[P3 Stoaker]

G'day Greenviews and all,
Wow, I just read your post, unfortunately I cannot offer much help with your questions. I certainly agree though that a solid base seems essential as collapsing or crushing would cause catastrophic damage. I have also had it stressed to me here on the forum, not to be afraid to undo work and go backwards to get it right. I know none of us want to hear that but if that is whats required to get it right then so be it !!!
I am doing an oven a little larger, 21' 21/32" radius ( metric at 550 mm) but I'm considering a slightly lower dome centre, around 500 mm (19' 11/16"), or even 480 mm. The reason for this comes from a local oven builder and he claims with the centre that little bit lower performance is significantly better. 2 questions, firstly, I haven't put that idea to the many many years of experience here on the forum and secondly, how to build. This local chap builds for a living so needs to achieve quick results, he cant wait around too long for mortar to set before laying the next course. What he does is lay the first 4 courses and then builds a sand mould inside. This allows the dome to be completed quite quickly as drying isn't a problem. Apparently the inside mortar joints often need a little touching up which is done after the sand is removed.
If performing this build, or any with a somewhat lower dome I do wonder how to use the IT tool?? I think you could just shorten the length each course, and I think the tool will still set the correct angle each course. the length of the tool for the previous course is obviously known, and the final top course. Question will be how to evenly split the shortening of the tool each course.
Do you know where Russell posted the info about the dome vent?
Kind Regards
Greg

[GreenViews]

For others browsing, I came across this thread: https://community.fornobravo.com/for...ent#post423442 which seems to indicate that I'm being way too impatient with this cure time. I'm not sure I want to wait a week or two to start building my dome, but it seems to be getting harder all the time and maybe in 2 days (after the rain tomorrow) it will be hard enough to start the underlayment layer and first course of the dome without me scraping it off and redoing this 3/4" layer.

[GreenViews]

Help, I may have goofed! To correct the unevenness, large gaps and minor crumbling in my CaSi layer, I decided to add a 4:1 perlite layer on top. About 3/4" only. As suggested, I plan to put bricks on a fireclay/sand layer on top of this. Instead of 5:1 perlite: portland I used 4:1 perlite: Acona medium duty refractory mortar. 12 hours later, there were soft and crumbly spots. I'm pretty sure I mixed up really good, maybe not enough water in spots? I sprinkled more of the refractory mortar on top and wet it with a spray bottle and trowled it in a little. Now it is pretty hard most spots, but on edges there are a few crumbly and soft spots still. The Acona product has a warning about portland, so perhaps it is similar to homebrew? Not sure. Should I have used just portland? How long should it take to set up? Am I being too impatient? With all the warnings I've read about portland chemically breaking down under heat over time, I was nervous about using it in the perlite layer right below the brick. How hard does this 3/4" layer need to be? Too many questions, but I'm nervous about the foundation for my dome which is why I tried to improve on the stability of the CaSi board in the first place.
Any advice? A) scrape it off and use it for insulation around dome later, forgetting about the heat loss through CaSi gaps and don't worry about stability of that B) probably good enough if your finger makes a small impression in it, but 2 blocks stacked don't, go ahead with clay/sand layer C) add more mortar to top or scrape off and mix in with more mortar or portland and re-apply. I'll do my best next work day if I don't hear back from anyone with advice. When I picked up another 350 firebrick today I also picked up some firestop 50 refractory mortar. Anyone know if that is better than the akona product? Thanks in advance and I'll go out and put my saw together now and cut my subfloor bricks and try not to worry about this yet hoping the right answer will come in time. https://photos.app.goo.gl/N539Z6rRNeVXL6Wd9

[GreenViews]

Thank you JR. I will be adding a layer of splits on top of the full layer I have shown and definitely do it with that layer!

[JRPizza]

If you have not cut your bricks yet have you considered a herringbone pattern for the floor? Folks had posted that an angled pattern helps keep the peel and any cooking utensils from easily catching on brick edges.

[GreenViews]

Had just a couple hours to work on this today and the unevenness, large gaps and flaky nature of the CaSi I purchased was really bugging me so I covered only the top so CaSi wouldn't pull moisture off too quickly (not bottom of CaSi which is left with only metal mosquito screen so It could drain) and added a layer of 4:1 Prateperl to refractory mortar. The Prateperl I purchased on Amazon and is a very uniform, fine perlite which allows a smooth texture and the refractory mortar was purchased at Menards. This is not standard material nor standard practice and possibly the wrong thing to do, but I was concerned about structural integrity so made my best judgement for better or worse. The 4:1 mix will have slightly higher strength than 5:1 but lower insulating value, but that's ok because it is the layer between the brick and the insulating layer so hybrid function not a problem I think. Will foil on the top surface of CaSi trap water/steam in that for some reason doesn't drain out the weep holes below? Time will tell I guess.

Tomorrow I hope to buy more bricks, assemble the tile saw I bought and cut some brick if my free time allows.

[UtahBeehiver]

The 50/50 does not have to be a slurry it can be dry mix as well.

[GreenViews]

Thanks, I actually saw your comment this morning about dome venting and added something similar to my Amazon list for purchase when I get closer to insulating dome. Appreciate the feedback. I was considering just something on top of the board to keep the wet mix to be dried out too fast via the CaSi board. I guess I was also for a minute thinking it might protect the board from moisture from top, but I guess not such a great idea then. Can I put either a thin clay/sand moist mix or a pcrete mix right on top of the CaSi safely without too fast drying out? I'm actually at the moment leaning toward a 1" layer of 4:1 perlite: refractory mortar layer on top of the CaSi board since my board came kinda broken up and I purchased a single bag of Pratiperl, which is a much smaller, more even perlite that I might use there to give me a smooth surface and keep the cheap perlite for butressing half soldier course and encasing the edge of the CaSi to keep it from breaking apart by my feet hitting it, etc.

[UtahBeehiver]

Wrapping the CaSi board with aluminum foil to keep water out can also keep water in, water has what I call "sneak-o-sity" so by layering the board will also keep the water that finds it's way in trapped. You need to consider a vent at the apex of the dome so when water converts to steam, it has an egress point rather than building interior dome pressure. I just recently posted what Gulf and I used for venting the dome (actually Gulf's innovation)

[GreenViews]

I've seen people cover their CaSi board with aluminum foil to keep moisture off from the next layers. I have some FSK paper left over from a project https://jrproductsinc.com/product/fsk-paper/ but I decided to just use aluminum foil here since I don't know what chemicals might have been used for the fire retardant properties and this layer might get pretty hot. I think I'll cover the outside of my dome insulation with it where the temps will be cooler as a outside in vapor barrier there to keep any leaks from getting into the insulation, but with a slit at the top I suppose to allow any steam to escape the oven.

[GreenViews]

Just found answer to how to level the bricks from UtahBeaver posted to another build:

"06-05-2020, 11:31 AM
1. FYI, you do no mortar the floor bricks down, they need to free float for expansion and contraction. Same with joint between floor and first half soldier. You can do a 50/50 sand clay slurry if you need to level bricks but not a setting mortar. 2" 5 to 1 por v crete equal to about 1" CaSi

2. Up to you on the bevel,use you IT to see what the angle is and decide it you want to bevel the top of the soldier, my guess the angle on a 1/2 soldier will be slight Half soldier is better than a full soldier, less outward pressure from the dome."

Still considering what to do about the sub-floor bricks. With the height difference I'm not sure I want to add 3/16" of sand/clay mix extra between the layers and if the point is for the bricks to float, then they may eventually settle a bit if my height differences are too great, or so I reason. Also, possible heat transfer difference with older bricks and different type of brick. Even though I have a split layer to add above this, I fear it may still affect hot or cold spots. If I don't hear back from someone before I start on this, I'll just save the old firebricks to use near the top of the dome. A higher heat transfer brick there may give me good results anyway and most have clean enough edges for inside face. So I probably just talked myself into doing that. maybe I'll shave down the main high spot on the CaSi board. I considered adding a fairly thin layer of 5:1 perlite to even out and make up for poor seams in CaSi, but not sure I need to and then I'd have to wait a day. I do have lots of bricks to cut and saw to set up. Will consider as I start work in earnest today. I plan to mix up some 5:1 for around the CaSi to keep it contained and from cracking anyway. Will get a feel for how easy it is to work with at that time.

[GreenViews]

Some questions at this point:
a) my CaSi board cut out was messy and imperfect. Should I worry about the 1/16" gaps at places between the board? Also, at least one place is slightly higher because of a width variance in the board, which also arrived with some cracks in it, but I'm not thinking of worrying about those.
b) Turns out the used firebrick I saved for the oven floor only covers 2/3 of it. I hadn't calculated. These are possibly a medium duty firebrick where the new ones I can get locally are a light duty. They are also slightly (about 3/32") different width. Should I worry about the different heat retention properties if I mix the different types in the subfloor layer? (I plan for a layer of splits for cooking surface on top of this layer). Also, what should I do about the thickness difference? fireclay/sand layer to even out is what I remember seeing in forum. 50/50?
c) I could put the old brick in the center and the new brick around the edges in case there is a heat transfer variance noticeable from this thermal layer. Sound good?
d) I also have some old clay bricks, both red and yellow, some of the red ones are better quality for high temp it seems (high pitched clink when knocked together). Should I try and use these? The problem is all the dimentons are a bit smaller than the old fire brick even though the height matches that of the new firebrick, but I could save money putting them under my dome base? I'm going to avoid using them unless someone suggests I should because I can afford to buy new firebrick. I still hope to use the old firebrick in the floor.
I'll do my best tomorrow if I don't get feedback, but very happy for any advice. Wish me luck

[GreenViews]

Some work done on oven today. Slower than I hoped. Weep holes, metal screen, CaSi board, started on subfloor thermal layer, then created a temp shelter for the project.

[GreenViews]

I strongly recommend the forward placement. You will want not only want to reach your door, but reach into the oven. My front arch is 8 inches from the front edge of my stand. I love the position. I can reach in and dump a load of charcoal from my 'mini chimney starter' into the center of the oven, then hand place kindling without bending at all.
Here's the front of my 42 inch oven with a 72" peel reaching all the way to the back of the oven. Should give you some perspective.

Thanks Mongo! Sounds like perfect advice to me. I did some more recalculating this morning regarding my build and placement based on your advice!