42" Pompeii Corner Slab dimension HELP!

[Denamontini]

Thanks again for taking the time to respond. I certainly didn’t mean anything insulting by “old” and “new” My grandmother’s oven in the Calabria region of Italy is still standing— she immigrated to the USA in 1921. I really wanted and envisioned some of the old school techniques, but I also have limited knowledge of the technical stuff. What do you think about weep holes and tiny mosaic glass tile sheets under a vermiculite base? (I don’t even know if that is possible... can you make a vermiculite base in a cast and carry it onto the cement/tile? Or is it way too heavy?) Its difficult to problem solve without the stuff in my hand and no experimentation. That’s why everyone’s opinions are so valuable to me. No decision has been made yet— but I have learned so much from everyone’s build. All in all, my goal is to make good pizza!

[SableSprings]

As David noted, the primary problem with the vermicrete insulation base is that it takes quite a while to completely dry out. When I first suggested using the mosaic sheets (small-tiles), I was thinking of an easy way to create an air gap (between the concrete slab and insulation) and to provide multiple pathways for water/moisture to escape out the weep holes. I think we're all on board with David's weep holes in the slab below the oven location. I'm thinking if you created the weep holes (note below), built your forms for the vermicrete or perlcrete pad, set mosaic sheets (upside down-so the connecting mesh is up), and then laid either garden or ground fabric on top of it you'd be ready to pour the insulation slab. Since the insulating concrete is reasonably light, the fabric and mesh should hold their position and keep the wet mix out...retaining open paths for water to drain out of the vermicrete into your weep holes. It would certainly be nice to create that air gap/drain system below a poured insulation base. ...and no, you don't want to be trying to move an insulation slab of wet/damp vermicrete or perlcrete

Still, you'd be looking at waiting several days for the base to cure and start drying before beginning your actual oven build...again to David's point. Then after the build, you'd probably need a slightly extended oven (firing) cure time to completely dry out the vermicrete/perlcrete base. I'm pretty sure this would work, but it shows why the ceramic board might be preferred here. I mean, you create weep holes, lay down the tile sheets (align with weep holes), set your ceramic board on top, and you are ready to start building the oven.

Note: The best way I've seen here to create the weep holes is to set 3/4" plastic pipe sections into the top slab form, so they protrude below the form and are just below the top of the projected cement surface. That way, you pour and smooth the concrete, then when the concrete is well set, take a piece of rebar and punch up each pipe section. That clears the path and hopefully creates a small "crater" around the pipe mouth...to help collect/direct any water down. Or, you just make note of where your rebar is before you pour the top slab and then drill through the green concrete. In either case, you will want to silicone seal some wire mesh over the bottom pipe/hole openings to keep the bugs from claiming a new home...

Hope that helps...but remember, these ovens will do far more than pizza. (p.s. I didn't take any insult from the old/new comment...I thought it was pretty funny and just had to have a little fun poke back. )

[Denamontini]

What is the science/math on the landing dimensions? I just sketched 22 x 15 landing area on a 42” diameter for no real reason. What is the logic here? Brick dimensions? Size of the opening? Just trying to think ahead before we pour the slab. Thanks in advance!
What? I cant upload a pic from my iPhone?!?

[RandyJ]

I am surprised if you cant upload from your phone . I did my whole build that way. You need to reduce the file size to unde 1 mb i believe. It will be easier to give opinions once we can see what you are trying to do .

[Denamontini]

Don't laugh at my simple drawing! Haha! Ok, you can laugh!

We decided that our cement base needs to be 72 x 72 square with the front chopped off at 48 inches. That would make our ground slab 80 x 80 with the front chopped off at 56 inches. In making sure the oven would fit properly on the slab, I made this crude drawing... which got me thinking about the dimensions of the landing. You cant't see it in the drawing, but I drew the landing 22" wide and 15" deep. Am I close? What is the thought process? Thanks in advance!

[SableSprings]

For that size oven, you will need to have an 8" diameter (ID) chimney. The landing and smoke gathering "funnel" into the chimney are determined by your build type, chimney system, access to the entire interior of the oven, and personal preference (do you want to have more space to rest a peel, pot, or pan coming out or going into the oven). In addition, many of us simply go by the materials available to us. My landing was totally determined by the desire to not have to cut any more bricks (I'd returned the masonry saw ) and the desire to use bull-nose bricks along the front of the oven landing. Creating the arches needed to support the upper smoke chamber vault and provide an interface to a SS chimney is going to be a big factor in how big your final landing area ends up.

Just to provide you some comparison numbers for my 39" ID oven...my landing has an ash dump cast/built into it, but it's 21" from the front edge of the bull nose bricks to the door seal/stop, 23" wide at the front with a 19" oven entry width (2" on each side for the door seal/close lip). Take a look at my build post (link in my signature line) and you can see how these work for my oven in The Dragonfly Den.

[Sampatch]

I built my 42” on roughly same size footprint base, 70x70”. My suggestion is to mock up the layout on the base testing WFO center point to base and fit between WFO reveal and your smoke vestibule / chimney design. make sure area you are allowing On WFO platform Is large enough to build all design elements. I wanted to be certain my smoke vestibule worked well with 8” insulated chimney so I made it as deep and wide as possible. Oven drafts fine, however I wish I would have built base at least 4 to 6 inches larger to better fit planned insulation layers inside the dog house frame. Laying out smoke vestble and oven center on the base is a good early step, test your assumptions.

[Denamontini]

We had an unusually warm day and we are expecting 4 warm days so we did the slab today. 80x80

[RandyJ]

Congratulations looks nice.

[Chach]

So it begins. No turning back now lol

[Denamontini]

Thanks! I will need lots of help and advice once we get going so at a certain point I will change over to a “build” post. I hope you guys will stick with me. I’m really feeling the vermiculite base and so I wanted all ideas on weep holes, upside down mosaic tiles, mesh and whatever else you have dreamed up. I am especially curious about things that people didn’t do on their builds, but thought of afterwards.
Thanks in advance! My neighbors think I’m crazy!