New 42" Pompeii oven build in N. Texas

[chamilton]

Hey everyone!

I've been a long-time lurker and reader of all of the amazing builds on here, as I've been planning my own WFO build. Weather permitting, I will be starting on the foundation slab this weekend!

My wife and I own a Delicatessen / Specialty Market, where we currently serve breakfast and lunch. I've built an outdoor courtyard where we will serve dinners on a reservation-only basis on weekends. It's not a large space, with seating for about 40-45 people. We will offer other options besides pizzas, although they will certainly be the star of the show. I'm going to be building a 42" igloo style, and have most of my plans worked out (in my head at least!), but would love to run all of it through the collective wisdom of all of you who have built / are currently building!

Here's what I have planned so far:

For the foundation, 5.5" of structural concrete and rebar, over 3" gravel. The foundation will be 69" x 116" (the extra depth will give me a 3' landing in front of the oven to stand on).
For the base, I'm building the standard cinder block structure, with concrete filling every other hole. Open to the front for wood storage, with angle iron to support the course above the opening.

Here's where things start to differ from the standard builds I've read on here. My long-term plans for the oven are still up in the air. We may move the location of the courtyard in the future, so I'm wanting to build it such a way that I could lift the hearth slab and oven with a forklift in order to move it if I needed to. In order to make sure it is stable enough to move, here's what I'm thinking: For the top course of cinder blocks, I would use the shorter solid ones (after filling every other hole below that), and use construction adhesive to attach the top course. Then, lay thick steel flat plates across the top of the base (with notches ground out of the top cinder blocks so they lay flush. When I build the form for my hearth slab, I would attach cement board or plywood to the underside of the steel plates while pouring the concrete, so that I could remove them afterwards, and the steel plates would be left flush with the bottom of the concrete. My thinking for this is that if I lifted it later with a forklift, the plates would provide additional strength and support during the move.

For the hearth slab, I'm planning to pour 3.5" of structural concrete with rebar, and 4 drain holes under the oven floor. The hearth slab will be 69" x 80", if I've done my calculations right. I'm figuring the interior of the oven at 42", plus 9" for brick (4.5"x2), plus 6" for insulation blanket (3"x2), plus another roughly 8" of exterior material (4"x2). I'm planning to stucco the exterior. That leaves me with about 2" on each side of the oven. The 80" depth of the hearth slab is based on an 8" vent landing and a 12" oven landing. After the dome is built, I'll do a second pour for the oven landing to bring it up level with the oven floor.

For floor insulation, I'm planning to use the 2" FB insulation board from Forno Bravo, laid on top of ceramic tile sheets for drainage. I've seen several builds using foam glass as additional insulation underneath the FB insulation board. Is this necessary / beneficial? Would 2 layers of FB insulation board be better (giving me 4" of insulation)? I'll then use dry sand/fireclay as necessary to level the floor for the firebricks.

Okay, that's probably way too much information for a first post, but I needed to dump some of this out of my brain!

My questions for now:
1. Any thoughts on using the solid cinder blocks for the top course to give a solid layer to rest my hearth slab on?
2. Any thoughts on using the steel flat plates under the hearth slab?
3. Any thoughts about the feasibility of moving the hearth and oven with a forklift down the road?
4. Any recommendations for the floor insulation (1 layer of FB board vs 2 layers vs a bottom layer of foam glass)?
5. Any other concerns or warnings for me about what I have described?

I am so beyond excited to be finally starting on this project! I will have lots of additional questions as I continue along, and I want to say thank you in advance to anyone who can lend their expertise / experience.

Cheers!

Chris

[Kvanbael]

Interesting challenge. Solid block plan sounds solid. You lost me on the steel plates though. I would also consider some plastic sheets between walls and heart, to facilitate then coming loose. No way the heart will budge given its final weight. ) And you can insert loose metal or wooden beams between fork and heart, when time has come to lift.

Check if your pavement is suitable for a heavy loaded forklift. You might end needing a crane.

[Pizzarotic]

My questions for now:
1. Any thoughts on using the solid cinder blocks for the top course to give a solid layer to rest my hearth slab on?
2. Any thoughts on using the steel flat plates under the hearth slab?
3. Any thoughts about the feasibility of moving the hearth and oven with a forklift down the road?
4. Any recommendations for the floor insulation (1 layer of FB board vs 2 layers vs a bottom layer of foam glass)?
5. Any other concerns or warnings for me about what I have described?

Wow, 69" x 80" hearth is massive and almost a ton of concrete alone. You may want to check your math. 42" oven, 9" brick, 6" insulation, 2" render is 59". What is the other 8" of external material?

Anyway Q1&2. I think you are over complicating things.
Just block up the base as per normal and core fill. Lay a sheet of fibre cement on top and form up your hearth slab and pour. You don't need steel under the slab. The steel goes in the slab and will be way strong enough.

Q3. Should be fine

Q4. Minimum 2" of ceramic fibre board is recommended. 4" might be overkill. The foamglass makes a good moisture barrier between the slab and the ceramic fibre board but not critical.

[Pizzarotic]

For the hearth slab, I'm planning to pour 3.5" of structural concrete with rebar, and 4 drain holes under the oven floor. The hearth slab will be 69" x 80", if I've done my calculations right. I'm figuring the interior of the oven at 42", plus 9" for brick (4.5"x2), plus 6" for insulation blanket (3"x2), plus another roughly 8" of exterior material (4"x2). I'm planning to stucco the exterior. That leaves me with about 2" on each side of the oven. The 80" depth of the hearth slab is based on an 8" vent landing and a 12" oven landing. After the dome is built, I'll do a second pour for the oven landing to bring it up level with the oven floor.

You Texans alway go big! Gotta love Texans!

[chamilton]

Hey guys, thanks for the responses!

I've made a couple of modifications to my original plans, and have finally gotten started. I poured the foundation on Monday. 70" x 116". In case anyone is wondering, that took 56 bags of 80lb concrete, and 25 bags of gravel underneath it. Needless to say, I was moving pretty slow on Tuesday!

I searched around for someone to deliver the concrete, but couldn't find anyone around here that would handle that small of an amount. I rented a mixer from Home Depot, and it ended up taking about 2 hours for my wife and I to mix and pour all of it.

Pizzarotic, you're right - I was overcomplicating the base and hearth. I'm going to just use cement board under the hearth, and drop the steel plates idea. Lots of rebar in the hearth.

As for the size of the hearth, I was counting 42" for the oven, 9" brick, 6" insulation, 8" exterior finish, and 4" render. However, I've realized that the exterior stucco finish won't need 4". So if I drop that down to 2" thick stucco (x2), that should drop the hearth width to 65".

Related to the floor insulation, I've seen that most of Forno Bravo's commercial ovens have 4"of insulation. That's what got me started thinking about it. I'm planning to bake bread in it as well, so I'd like to insulate it as much as possible within reason. I'm still having an internal debate about that.

Next step is the cinder blocks. I ran rebar up through the foundation slab, and am planning to mortar the first course of blocks to the foundation. When I go to fill the holes with concrete, so I need to do anything to help the new concrete adhere to the existing foundation concrete, or is the rebar enough? I can't imagine the base could ever move once all is this weight is on it.

Kvanbael, thanks for bringing me back to earth on my thoughts about moving it. If I do move it, we will only be going across the property, so worst case we would tear up some grass and create some big ruts to fill in.

And yes, Pizzarotic, we always go big! If I'm going to kill myself building a WFO, it's going to be a beast!

I'll post pics of the area where I'm building it, and my progress as I go along.

Thanks again for the responses!

Chris

[SableSprings]

Welcome Chris (& your lady)! Sounds like a good start. Some things to think about;
1) Make sure to support the cement board in the center span area before you pour your top slab...don't forget to put in some knock out shims (the weight of the concrete will lock that support down & make removal extremely difficult without the shims).
2) Path to the kitchen & prep/holding area. Counter space near the oven (both before & after cooking items) is going to be very important. Loading the peel with the pizza, working the item(s) in & out of the oven, putting the done pizza(s) on a board/table for cutting & plating...all "eats up" counter space!
3) Running the oven for any length of time is going to use a lot of wood. I'd strongly advise you use create a wood stack area off to the side for easier access during cooking. Having to bend down & constantly go in after wood under a working oven will not make you happy! Also, having your main wood supply nearby is going to be important as will a plan for ash removal.

Looking forward to your progress & some pics!

[chamilton]

Hey Mike!

Thanks for the response! Great suggestion on the shims ... I wouldn't have thought of that, and would have ended up having to cut them out!

I've been thinking about integrating a prep table off the side of the cinder block base. I saw one where they had added metal braces between cinder blocks to attach the prep table to. I'm going to try to draw something up for that this weekend. My goal is to set the cinder blocks on Monday.

I hadn't thought about the wood stack. It makes sense that bending over constantly would get old! I'll have to give some thought as to where and how to store it. Any suggestions about whether I should build a full enclosure for the main wood supply, or just a cover for it?

Ash removal ... short of dumping it into a metal bucket to cool before disposing of it, do you have any other suggestions? I have a dumpster on site that I guess I can dispose of them in. What else do people usually do with their ashes?

These are great things I need to be thinking about. If you think of any other potential "gotchas" as I'm going along, I would appreciate your input.

Thanks!

Chris

[Pizzarotic]

As for the size of the hearth, I was counting 42" for the oven, 9" brick, 6" insulation, 8" exterior finish, and 4" render.

I still don't understand what the 8" exterior finish is?

However, I've realized that the exterior stucco finish won't need 4". So if I drop that down to 2" thick stucco (x2), that should drop the hearth width to 65".

1/2" Stucco is the norm and more than adequate.

[Pizzarotic]

What else do people usually do with their ashes?

It's great for the garden

[SableSprings]

Quote: "Ash removal ... short of dumping it into a metal bucket to cool before disposing of it, do you have any other suggestions? I have a dumpster on site that I guess I can dispose of them in. What else do people usually do with their ashes?"

Chris, I built an ash slot into my hearth & have a metal container (with lid) just below the slot. That allows me to pull the ashes into the container as necessary and lets me dump them in the compost pile much later (after they've completely extinguished/cooled, guests have gone, & at my convenience ). Many garbage services will collect ashes (bagged & cooled...lots of plastic garbage bins out there with melted holes from live ash/coals ).

Obviously, you're going to need a fairly large main wood storage area both easily accessible to your daily "working" stack AND in a place where wood delivery/dump is practical. I would have that main wood storage area somewhat shielded visually (tough areas to keep neat & clean) from my customers, so a 3 sided, roofed shed is my suggestion.

If you look at my build thread you can see my ash collection system and the carts I had made for supplies and wood. Note on my wood cart that I load it from the back door so I don't have to track (and clean up) the wood debris through my guest area. Gulf built a wood cart that slides underneath the oven from the front instead of the stand sides like I did.

Hope that helps.

[david s]

I compost the ashes. Their alkalinity balances the acidityof dried leaves.

[chamilton]

So, I finally have some progress!

I poured the foundation last Monday. Of course, everything took longer getting ready to pour, so it was 9:30 at night when I finished, and getting a little chilly. Please don't judge me on my troweling job on the foundation! It was still too wet to do much more than strike it off with a screed. Any attempts at troweling it were just making it worse, so I gave up and let it be. I'll take some diamond sanding pads to the areas that are visible later on.

Yesterday I started setting the cinder blocks. I mortared the bottom course, and dry-stacked the rest. For as rough as my foundation troweling was, everything leveled up really nicely. I've decided to use 4"x8"x16" solid blocks on the top course, in part because I was getting worried about the height of the oven floor, and in part because of my crazy and probably impractical plan to be able to move the hearth and oven later if necessary.

I ground out the grooves for the angle iron to sit flush, and am going to use construction adhesive to attach the top course of solid blocks. But first, I'm filling every other hole with concrete this afternoon.

I think I've decided to put a thin block wall running down the center of my base to provide extra support. Taking from Mike's idea with carts, I'm thinking I'll build two carts to fit on either side of the divider wall. I'm planning to build a covered wood storage area behind the WFO, and a path from it to the front of the oven to roll the carts on.

Here are my first pictures. Like I said, please don't zoom in and judge my foundation troweling job! The second picture, taken from behind the oven, shows our existing courtyard. It too is still a work in progress. I'm going to expand it, and add more tables. And we have lots of plants and greenery planned to go throughout it.

With any luck, I'll be pouring the hearth slab this weekend. I still need to finalize the exact size needed between now and then.

[Stlavsa]

Any progress on this? I am at the point where I am ready to pour my hearth and I am deciding if I want to add any extra support in the middle like you did my dimensions are 54 wide by 64 long for the 36" casa. I am concerned that at these dimensions, the oven will fit squarely inside the block, and the hearth alone will handle all the support (rather than the oven sides extending over the block walls for support.) Part of my hiccup is, that I am installing the gas burner, so If I throw in a support column it will kind of "be in the way". Still like the idea of a half block support column in middle, probably better safe than sorry.

[fhausback]

You can readily span 64" with your slab. You'll just need to make it thicker, and add more reinforcement. I wouldn't trust my buidling skill to make a 4" thick suspended slab span 80", so mine is 6" thick minimum, and i overdid it on the rebar. (rebar was much cheaper when i built my slab 2yrs ago).