Neapolitan oven restoration

[Odin]

Hi,

It is my first post on this great forum.
About two months ago I've decided I want to build pizza oven and spent some time researching my options. Dome shape or barrel vault?
Luckily ( or not) I have been offered for free Neapolitan style commercial pizza oven. The only cost was to move the oven. As this was a big one (110 cm external diameter) I had to hire Hiab truck to move it to my property.
Attached you can see couple of photos of the oven. Outside it is in poor condition. Cast iron layer rusted ( oven kept outside) and insulation below fire brick hearth crumbled. Although dome and hearth fire bricks are in very good condition.
My plan is to remove cast iron shell and remove concrete render just to keep dome and hearth. Cast Iron heavy duty stand requires only hammerite paint touch.
If you are interested in disassembling low dome oven let me know. I will upload more pictures of my work progress.

Peter
Perth (WA)

[SableSprings]

Good to have you on board Peter. I for one will be very interested in seeing your deconstruction/reconstruction process. Are you planning on lifting the dome and hearth onto a new insulation base? What's the object below the oven?...an old mixer or just a support jack (or an old mixer being used as a support jack ??)

Looks like they may have had a crop of wheat harvested from the top pan...

[Odin]

Mike - yes I am planning to move dome and hearth to new base. Current one literally crumbles. When oven was moved to my property it was put on a pallet so I can use stand to create new base and then is my deconstruction is successful I will move hearth and dome to.
Today I have removed one side of steel layer. It was easier than I thought. took about 5 minutes with my angle grinder. Between dome and steel, there was about 2 inch layer of clay. I am planning to clean the clay and maybe use later in my restoration process. As you can see in attached picture there is no other insulation than clay steel and above the dome - something that looks like concrete with small lightweight stones.

[SableSprings]

I wonder if the clay was used to increase the mass of the oven (and consequently it's ability to hold temperature). Do you really need to clean it off? If the interior is in good shape there wouldn't be any real need to take it all apart and rebuild. Putting it on a new insulation base and adding external insulation might be all you'll need to do to make a functional oven (other than making it look nicer outside to keep friends and family happy).

Looks like the lightweight stones may be pumice (or large pieces of perlite) in a cement/lime matrix. As insulation board for the base of these ovens is usually a bit expensive, many of us have opted to use a base layer of perlite/cement (perlcrete) or vermiculite/cement (vermicrete) mix. The ratio is 5:1 (insulator to cement) for a base and 10:1 for a cover insulation. These insulation options take about twice as much thickness as the CaSil board and ceramic fiber batting to provide equivalent insulation value. Some folks have successfully used loose perlite or vermiculite to fill a box built around the dome instead of mixing them with cement to form over the dome. Batting or ceramic blanket and either perlcrete/vermicrete both have their pros and cons, but technologies supply the insulation needed when applied correctly.

When planning your new base, make sure that you can keep water out. The CaSil board will suck up water like a sponge as will both the perlcrete or vermicrete, so you have to think about that. David S (on the other side of OZ) advocates putting drain holes in the supporting base to allow any free liquid to escape. If you are thinking about simply making a steel box similar to the original, make sure you plan the outside metal sheets to overhang the frame so water doesn't collect anywhere...

[Odin]

You are correct - clay is an insulation layer and adds thermal mass to the oven. I have to remove it as while the oven was deteriorated outside and was exposed to weather conditions clay soaked the water, ants made the a nice nest etc. Also de constructing it is the only way to move it as the oven is bloody heavy.My plan is to take it apart first. Scrap concrete with stones ( pumice not perlite). Recover, clean and dry clay to a powder - easy in sunny WA. Transfer dome and hearth to stand with new insulation board. Then insulate, render etc. Sounds easy, but we will see how it goes.

For last few weeks I've been buying second handed oven supplies. I bot for cheap roll of insulation blanket with chicken wire on it, 100l of vermiculite. I also have 2 kiln shelves (70x120) made of lightweight refractory material and I am thinking if I can use it as and insulation for the base.

[Odin]

done some work yesterday. I removed one cast iron side and recovered clay that was under it. I managed to remove the dome cover - pumice concrete mix, Luckily it was not mortared to the dome just isolated with clay.
Now I can see the dome. It is pretty big...

[Odin]

We have weekend and some time to work on the oven.
All stainless steel walls are removed. I have bucket loads of clay that I don't know if I will need. Just in case I have cleaned it and keep aside. Finally I can see the dome shape. I was able to lift it above the brick floor for about 3 cm. I will need 2-3 guys to securely move it to a different pallet.
Now I am planning to work on stand. Have to wire brush it and weld caster wheels before I will start pouring what is below hearth.

[SableSprings]

Any more progress Odin? It looks like building a front arch and chimney vent is going to be pretty straight forward. The actual oven "dome core" looks to be in pretty good shape. Is there a slight outward angle on the entry arch (wider on outside, than inside)?

[Odin]

I have cut flange plates and now I'm waiting for specialist to weld them to my stainless steel table so I can mount caster wheels.
Entry is the same width inside and outside.
Dome looks ok. I was going to pressure clean excess clay from it but changed my mind.
you say front arch and chimney should be easy and that part worries me most. Originally flue diameter is 20 cm and I want to keep it that way. I am still not sure if I want stainless steel or brick entry.
attached 2 pics. which one would perform better?

[Odin]

[SableSprings]

Having an actual chimney to take the smoke "up and away" is a good thing. Until I put some height on my chimney, I had several start-up fires that put too much smoke back into head level...
I see the potential of a lateral breeze pulling smoke out the sides of the checkerboard open entry...and I really like being able to use my fire door to dampen down for an overnight pre-heat. Doesn't look like the checkerboard oven pic really allows for the option of a door.

I'm also a pretty big fan of having more of a landing to work with...so again, the second photo (white render) would be the style I would aim for. It's so nice to have a place to rest a pot and check the contents to see if it needs more oven time or to help spin a sheet pan of biscotti .

I used a terra cotta flue liner and did a brick facade for my chimney...for you, a brick arch entry with a little smoke collection chamber above connecting to a stainless chimney would probably be the simplest. Lots of well documented builds on the forum that do it this way. The brick front entry always looks good (to me) and the stainless chimney looks great on all the forum photos I've seen (and on a Casa G90 I helped install). Several folks on the forum have used refractory mortar to cast a chimney and they also turn out looking very slick & efficient. Sounds like you've still got plenty of time to decide what will work best for this rebuild (and for your comfort level), so keep plowing through build threads.

[Odin]

last day I was working on the oven and now it is completely disassembled. I have separate stand, hearth and dome.
I have welded flange plates and mounted caster wheels so my oven can be moved.
After removing rust and painting trolley I will be starting to install the floor. I am planning to pour 2 slabs (60x120 x 10cm) of vermicrete (5:1) in a wooden mold.

I have couple of questions for more expereienced users
1 do I need any reinforced bar/mesh in my vermicrete slab?
2 do I need to make a wall of frame of plain concrete to trap vermicrete inside?

Thanks

[SableSprings]

Good progress on the oven. You don't need any internal reinforcement in the vermicrete slab. Vermicrete and perlcrete (when cured) both have plenty of compression strength to support an oven resting on top. The problem is that both, though they are hard to compress, are easily crumbled if you hit the edges...I did make a "frame" of concrete to protect the edges of my perlcrete insulation base from accidental construction damage.

1) I suggest you skip adding any internal reinforcement (it only serves to degrade the insulation effectiveness).
2) Either make a frame/form of mortar or concrete around the perimeter of the insulation layer or add a thin coating of mortar around the edges of the vermicrete after you remove the form. Remember that this is only to help protect the vermicrete from damage and does not need to be very thick...

Also don't forget that you don't want your oven walls resting on anything other than the vermicrete.

[Odin]

thanks for prompt reply.
To protect crumbly edges putting tiles would be ok? Is my 10 cm planned thickness of vermicrete enough?

[SableSprings]

Your 10 cm vermicrete floor should be just fine. The rule of thumb is 2:1 ...for perlcrete/vermicrete, use twice as thick a layer as you would with ceramic board. Since 5 cm (~2" ) of ceramic board is commonly used for the floor insulation, your 10 cm of 5:1 vermicrete should work just fine since you're not looking at holding the oven temps for days at a time. The floor insulation layer depth is often a deciding factor, since the difference between 5 cm and 10 cm can make a difference in the build...a significant advantage to using the board insulation which is also a bit pricier .

If you are going to tile the outside, putting cement board around the vermicrete edges might provide a better base for the addition of thinset & tile. This would be the best option (IMHO ) if you were thinking of building your entire enclosure attached to a metal frame with secured cement board (& possibly metal lath) as the tile base.

Again, the vermicrete is crumbly and won't necessarily provide a good base by itself for the tile. If you are doing just a bottom edge of tile, I'd think about putting a strip of metal lath around the outside of the vermicrete, folded over and mortared at the top. Then, the thinset used to attach the tiles will act as the adhesive for the tile and to bind the lath to the vermicrete. I'm attaching some pics of the split brick facade I put on my oven which hopefully will give you some ideas...it was sorta like tile work