40” Pompeii in Rhode Island

[NewEnglandNewb]

I have been lurking on hear for a few years now reading through as many builds as I can. There is a lot of great information!

I have finally got to the point where I have most of my other projects around the house finished up and can start a wood fired oven build. I already built an outdoor kitchen on my back patio. When I designed and started that build I thought that using a portable wood fired oven (I bought an ooni karu) would be a good solution. Turns out my family really loves homemade pizza and a quickly grew frustrated with how small it is and the lack of heat retention. I started looking around for bigger alternatives and stumbled on this forum. I pretty quickly decided I need one of these in my life!

I love my outdoor kitchen and am not willing to tear it up to add a WFO, so I’m building one just behind it. It will be close enough to be able to use the counter for prep, but won’t be under the roof. The WFO is also too close to my property line to build a separate structure over it, so it will be exposed to the elements.

The plan is to build a Pompeii style oven with a 40” ID. It will be built on a round stand that will be clad with stone veneer to match my kitchen. I laid it out with the plan to build a round enclosure around it and a conical roof with slate shingles. I do really like the look of a dome and am considering a change to keep the igloo exposed. I am in an area that has winter with a lot of freeze/thaw cycles so I realize that isn’t ideal. Has anyone in a similar situation used a proper waterproofing solution over their dome (like flexcrete or thoroseal) and regretted not building an enclosure?

Here is my kitchen, the finishes on the WFO will be similar.

[NewEnglandNewb]

I started with digging a 6’ diameter hole that ~15” deep. I filled 8” with compacted gravel and formed up the slab. The slab is a 8” deep X ~16” donut with the wood storage area thickness reduced to 4” thick. I bent up some 1/2” rebar, then got to work mixing concrete.

[NewEnglandNewb]

The next step was the block work for the base. I used 8x8x8 CMUs so that the shape was a close to round as possible. I glued them together using PL500 on bond, then filled all of the cores with concrete and rebar. I also stuccoed the inside gave of the blocks before starting to form out the hearth since it will be much easier to access at this point. The plan is to have an arched entry to both the front and the back so I can have better access to the wood storage area.

[NewEnglandNewb]

Then I started building out the form for the hearth. I definitely didn’t make my life easy making this thing round. After scratching my head for a while I came up with a plan that I think will work. I built a table in the wood storage area and put a coupe of sheets of durock over that. The rest of the form is made from a sheet of plastic used for a wall covering in a bathroom or other wet space (the white plastic in the pictures) with a couple of sheets of hardboard as reinforcement.

I laid out where the oven floor will sit on the hearth and added pins to cast weep holes under the floor as well as around the edge of the dome where the blanket insulation will be. That should provide an exit path for any water trapped between the dome and the enclosure.

[NewEnglandNewb]

I should be able to get the rebar for the hearth cut and wired in place this weekend, but probably won’t get it poured until next weekend. It will be 4” thick with 1/2” rebar ~10” on center.

I’m starting the hunt for calcium silicate board and firebricks. I’m in the south west corner of Rhode Island (I can see CT from the my house), if anyone has suggestions for places to acquire either please let me know! I tired a couple of local places thought might have calcium silicate board with no luck. It looks like there is a distribution international in Sharon MA, so I may need to just drive there or suck up the shipping cost and order online.

The local building supply place does carry firebrick. They are Whitacre Greer brand that from what I can tell are a light duty firebrick. I was hoping to find medium duty. What are people’s thoughts on building an oven with light duty bricks?

[mongota]

https://community.fornobravo.com/for...es-medium-dutyI don't think I've seen anyone use a round base. Good to see a new style of design!

Brick availability is a constant issue, it's been discussed in many previous build threads. I'm sure a moderator will pop in, but I know in the past the recommendation has been if you can get medium, get them. If you can only get low duty, no worries, go with that. Top of my head, but I thought low was in the 1700F-2000F range, and medium up around 2700F. Flatbread cooking is done in the 900F range, while I seldom shoot temperatures anymore, I don't ever recall seeing anything over ~1150F. I can't see a wood-fired pizza oven seeing high enough temps and enough thermal cycles at high temps to cause a break down in a low duty brick. I know I've seen quite a few builds that used low duty bricks and I never saw a complaint afterwards.

If your look will be similar to the "stone dome" I have on my oven, my oven has been exposed to CT winters for quite a few years. Zero issues. The stucco render on my dome was coated with Thoroseal, it's vapor permeable. My stone veneer went over that. Any coating you put on your dome, I highly recommend it be vapor permeable. You always want to offer a path for super-heated vapor to escape. That might come off as a bit dramatic, but it's just good building practice.

Insulation? Good luck! Like I messaged earlier, I travelled a bit to find affordable and proper insulation. Hardest part of my build, as well as the most expensive, was the insulation, but I went with 4" of blanket over and 4" or board under.

Your ourdoor kitchen looks terrific. The oven will complement it well. Looking forward to your progress!

Firebrick link may be attached to my post. Not sure if it will work...

Best, Mongo

https://community.fornobravo.com/for...es-medium-duty

EDIT for spelling.

[david s]

IMO low duty fire bricks are fine for the dome, but medium duty is a better choice for the floor. High duty bricks are really hard to cut and will cost you lots in diamond blades.

[rsandler]

There's another recent build that did their base half-round (This one)--I guess it's the new trend! Looks neat, though I can only imagine the challenges in building the forms etc.

As others have noted, there's no great answers on insulation. It's expensive and hard to obtain. Another vendor similar to Distribution International is SPI which seems to have locations in New Haven and Worcester; not sure if either of those are better than DI in Sharon. One thing to inquire with the vendors is whether they have the insulation in stock or whether they'd do a freight charge to bring it in stock. DI in California needed a freight charge if I wanted it promptly, but was willing to waive it if I could wait for them to fill up a truck with other orders. But, conditional on paying the (exhorbitant) freight charge, they delivered to my house (more than an hour from their warehouse) for free. You'll have to figure out your own trade-offs of time vs. money vs. bother.

[NewEnglandNewb]

I got the hearth poured yesterday. I formed out arches over the front and back entrances to the wood storage and poured those monolithically with the hearth. 25 bags of concrete later and we got it done.

There was a 20% chance of rain when I woke up so I figured I would go for it. It started down pouring right when we finished mixing. We pulled out a tent and carried on.

My 15 year old daughter loves finishing concrete. She got the job of vibrating with a sawsall with no blade (including from underneath) and then got to work with a float.

It is now covered with plastic and a tarp to let it cure for at least a week. Up next is underfloor insulation, then time to start playing with bricks. My underfloor insulation plan is porcelain tile, 2” of perlite/vermiculite concrete, then 2” of calcium silicate board.

[david s]

I see you’ve planned for creating weep holes in the poured slab, good move.
Also if your plans are to cast a vermicrete slab over tiles, you’ll need to hold it up with some weed mat or insect screen so it won’t block the channels between the tiles.

[NewEnglandNewb]

Thanks david s. Yes, there are holes cast into the hearth under the floor insulation as well as outside of the floor/dome OD where the ceramic fiber insulation will be in case that gets wet to give the water an exit path. My plan is weed mat over the tile to keep the vermicrete out of the channels for the water exit path. I was thinking about extending pins up into maybe the first 1” or so of the vermicrete to give the water a better exit path out of the insulation. Bad idea? Overkill?

[UtahBeehiver]

Coming along nicely, 5 to 1 p/vcrete under the CaSi gives you enough strength. See attached.

[david s]

Yes, good idea. You should be able to easily drill up from the bottom about an inch into the vermicrete, then glue some insect screen over the holes from the bottom to prevent wasps blocking the holes up.

[NewEnglandNewb]

The plan for the p/v Crete is half vermiculite half perlite all mixed with a ratio of 5:1 with Portland cement. I think it was a post from david s that I saw which recommended combining the two.

I finished up a small extension of the patio to connect the WFO. Pretty happy with how that came out. I’m going to try and clean up around that area now to see if I can get some grass to grow before the whole area turns to weeds this summer.

[RandyJ]

I will be excited to see how this turns out. It is always fun to try a new and different design. I would definitely recommend not doing a igloo unless you are planning a substantial roof over head. Otherwise you are doomed to have water problems. I have seen a few have their vent come apart from freeze thaw cycles. Just my 2 cents.

Randy