Barrel/Vault Build in AZ

[Tat2Neil]

Hey guys (and gals) I recently got bit by the WFO bug after visiting a friends house and enjoyed some awesome pizza made from a small, medicine ball molded WFO. It was only able to make small personal size pizzas, but it definitely got the job done! And despite me now having BIG plans for a large, insulated, beautifully built in oven to someday grace my back patio, I realized that will take me weeks/months to complete since I have very limited free time, and is going to cost big $ and it’s Arizona in May which means it’s Already triple digits and I won’t want to work outside for another 7 months, but I can’t wait that long to enjoy my own backyard WFO

I need something quick, relatively easy to construct, small-ish in size, easy on the pocket book. Almost went the medicine ball route after seeing so many Pinterest examples, but I decided not too because; A) one article I read mentioned how the ball moved too much when trying to ‘compact’ the cement, and B) since I’m trying to maximize my overall size to interior cooking space ratio, the barrel/vault style oven is the obvious design option.

Yes, I have read many different things on how the dome is a more efficient heat equalizer and cooks pizza better, etc etc. But in the sense of versatility since my wife loves to make bread, and since I highly, highly doubt my ameture taste buds would notice any difference in a vault fired pizza or dome fired pizza, barrel build is a go!

Ok onto the good stuff

I started by drawing up my plans, I need the whole oven to fit on 24x36 platform and I intend to use every inch of it. (I’ll explain why the dimensions later) so by using a simple grid and the magic 62-63% door to ceiling ratio, I had My basic pattern. As well as trying to figure out s fire brick count for the base, but my dimensions were off, oh well, never hurts to have some spares.

[UtahBeehiver]

A platform of 24" x 36" is going to be tough to do. I do not see any allowance for insulation or bolstering on the side walls which "may" be required on a barrel oven. I know that David S has done 21" cast dome ovens but I am not sure one of these would fit on your base footprint. Maybe this small of a barrel oven will not require bolstering but that still leaves the insulation issue. Good luck building this in the AZ heat.

[Tat2Neil]

You are correct I did not plan on doing any insulation on this build. My school of thought is basically imitating the medicine ball oven process, but making my own barrel mold. I know insulation is a very good thing for these ovens, arguably a necessity, which is why if I build a larger all brick oven eventually I will allocate enough room to have an insulation layer. This one unfortunately due to size constrictions has to be extremely basic.

I plan for 3 inch thick walls all the way around, basing this off of the few examples I read about where they had 1.5 inch to 2 inch walls. Which I felt was too thin.

a 16inch interior ceiling, a floor surface of 18x24, and a 10 inch by 14 inch wide entry, and a one inch wider lip for a outer door.

so lots and lots of cutting up old boxes, and hot gluing pieces together (that part was actually a lot of fun) I finally had my simple positive mold.

[Tat2Neil]

I looked up homemade refractory cement recipies and the most common answer is found which was fairly consistent with the few other builds I read through, was mixing perlite with Portland cement with the additions of stainless needles. Although I opted to use fire mortar with my perlite, and mixed at s 4:1 ratio (per website instructions) opposed to the 5:1 ratio suggested in the medicine ball build.

It was a little challenging, and I only took one photo mid-cement laying, but I ended up with about 4inches on top and 3 on the sides (the far side looks thin in this photo because I hadnt quite finished that side.)

[Tat2Neil]

Here it is after everything was laid out. Thankfully I did this project under a very full grapefruit tree that offered me some shade whilst I was killing me back packing this stuff together, also offering a great covering from the sun while it’s been drying out the last 2 days, almost ready to lay on my wire and cover with more fire mortar and smooth it out.

[UtahBeehiver]

Well, looks like you done a lot of work. I am not sure which website you are talking about using a p-crete as core oven material. I am only familiar with the use of dense casting refractory or home brew mix that does "not include" perlite or vermuculite in the base oven structure then a p-crete coating for insulation. Hope the pcrete mix is durable enough to accomplish you cooking goals and all the banging and wood movements and such that goes on with WFO cooking

[Tat2Neil]

This was the site I ended up following for my mixing ratios and suggested use of perlite, particularly recipe #2

https://www.delftclay.co.nz/how-to-m...ent-3-recipes/

and this was my basic guideline for build process, i just changed a couple things along the way.

http://www.instructables.com/id/My-1...ed-Pizza-Oven/

Im aware this isnt the most ideal design, or build process, and it may crack in half after a couple uses, and if so I will be the first to say to not make the same mistake I did. But who knows, maybe it will work.

[UtahBeehiver]

Good luck. I would be curious on follow-up. We, on the forum, are always looking at other ways to skin the cat. We should start a thread for budgetary constrained ovens.

[Tat2Neil]

Good luck. I would be curious on follow-up. We, on the forum, are always looking at other ways to skin the cat. We should start a thread for budgetary constrained ovens.

Thanks. I apologize if my build is misplaced in this forum, feel free to move or delete it.

Love your build album btw, that copper finish work was stunning!

[UtahBeehiver]

No need to apologize, keep us informed on how you project works. There are not many if any builds that used a p or v-crete as the core shell material, at least that I am aware of on this forum, typically dense cast refractory or refractory brick. As mentioned in one the links in your post, the addition on SS needles was suggested for strength since the material gets crumbly near the edges.Even in dense castable refractory, SS needles are used.

[Tat2Neil]

Yessir, and I definitely followed that advice and have almost an 8% ratio of SS needles in my p-crete base.

[Gulf]

My fear is that, along with the crumbling pcrete, the needles will end up in your food.

[Tat2Neil]

My fear is that, along with the crumbling pcrete, the needles will end up in your food.

Even after I skim coat the inside and out with a refractory cement (which recipe I found on this forum) that calls for 1 part Portland, 3 parts sand, 1 part lime and 1 part fire clay?

[Gulf]

There is nothing wrong with the formula. It's just that I am not sure that it will adhere to the pcrete inside the dome and or last very long as a thin skim coat.

[david s]

Sorry, i’ve missed this entire thread until now. Unfortunately a perlcrete or vermicrete mix results in quite a weak structure with a surface that is particularly susceptible to abrasion. As it is very insulating you will have next to no thermal mass for retained heat cooking. Adding stainless needles to a weak mix will increase thermal conductivity a little and marginally provide more thermal mass, but as the mix is so weak(as you’ve already found) they will do little to increase strength of the casting. In addition the grains of perlite or vermiculite hold stacks of water, about twice as much as a standard concrete mix. This needs to be removed slowly otherwise the casting is highly likely to swell and crack, and I suspect this is what has happened in your case. Can’t really offer any further advice other than tear it down and redo with a dense castable mix over which you need a decent layer of insulation. Did you insulate under the floor?