Neapolitan oven restoration

[SableSprings]

I have measured my dome again and it has 120 cm external diameter with 5 cm walls. Table is 110 x 110 cm. After your advice I will lay the cement board on the table. It will be wider by 15cm on each side. That will give me 140 x 140cm floor to work on -120cm for dome 10 cm (5 on each side) of insulation and 10 for render.
I don’t want to lay another concrete layer as subfloor as that will make oven way too heavy to move. I am already struggling how many people will be required to move my table on wheels.

Just like you said I want to put cement board, on top of that pour cement-vermiculite mix, then clay (recovered from oven), hearth slabs and mortared dome.
I am not giving up yetJ

I think that's a very workable plan. I agree on avoiding a concrete subfloor...I just wanted to make sure you had several options available. I don't know if you saw the thread where an oven was lifted as one piece together with its base (by crane to a flatbed truck) and was moved about 5 miles...it turned out to weigh 13,500 lbs (over 6,100 KG) with the cement foundation and block stand...wow! I suspect that your rebuilt oven (even though much lighter than that) won't get moved very far or very often

[Odin]

I have measured my dome again and it has 120 cm external diameter with 5 cm walls. Table is 110 x 110 cm. After your advice I will lay the cement board on the table. It will be wider by 15cm on each side. That will give me 140 x 140cm floor to work on -120cm for dome 10 cm (5 on each side) of insulation and 10 for render.
I don’t want to lay another concrete layer as subfloor as that will make oven way too heavy to move. I am already struggling how many people will be required to move my table on wheels.

Just like you said I want to put cement board, on top of that pour cement-vermiculite mix, then clay (recovered from oven), hearth slabs and mortared dome.
I am not giving up yetJ

[SableSprings]

Peter, are you planning on putting your cooking floor sections directly down on the vermicrete (of course with a thin clay/sand layer for leveling) and then setting the oven on top of them? If you do it that way, the weight distribution on the vermicrete is very different than if the dome itself rests directly on the insulation. If you plan on setting the oven on top of the cooking floor then I would see no problem with pouring the vermicrete directly into the concrete board based form (that is sitting on the steel cart). Again that elephant foot weight distribution thing... Also doing it that way takes care of the issue of the dome dimensions being larger than the metal cart top...the cooking floor is distributing weight more evenly for you.

[SableSprings]

Yes, the sketch looks like what I was thinking. (My only concern is that you make the vermicrete pad large enough so the oven does not come down directly on the edges of the pad...remember, compression strength only. I'd want to have at least 1-2 cm of pad outside the oven footprint.) I would simply set form side boards directly on the cement board while on the stand and then pour the vermicrete right in. You've got several nice support pieces across the stand mid-section now so why do this in two steps (pour & move) when you can just set the cement board on top of the frame, set your form sides in place and pour the vermicrete directly into its new home.

I don't know what "slightly bigger" means here, but I would think if the oven is only a couple cm wider on each side than the stand it shouldn't be a problem.If it's a concern to you, there's a couple of options I can suggest. 1) The best option (but heaviest) would be to put down the cement board and pour a pad of 8-10 cm thick reinforced concrete larger than the oven footprint and then form up again and pour on the 10 cm vermicrete layer. 2) You could put in some angle iron either bolted to the frame along the sides under the cement board or cut and embedded in the vermicrete pour to give it extra strength on the sides without pouring a reinforced cement pad base on the stand.

In either case, I'd use the thicker variety of cement board that's available...here it's 1/2" so you'd probably be looking at 12-14 mm. Normally we have two thickness sizes of Hardibacker available here, 1/4" (6-7 mm) and the 1/2" (12-14 mm) so I'm assuming it's similar for you. The thicker board does not flex while the thinner board does.

Remember that the weight of the oven is going to be distributed on the base...kinda that elephant foot concept. Also remember that you are going to be adding insulation and some type of enclosure over the dome, so allow for the extra layers. I feel like I keep throwing wrenches into this project, but you're doing great. Better to think about your options now and make a decision that YOU feel comfortable with.

[Odin]

Thanks!
That all looks clear. To confirm I’ve created a sketch.
Vermicrete should be poured on cement board or laid on it after curing in my mold? What is desired cements board thickness?
I have another obstacle on my way – I have measured my dome and it is slightly bigger than my table.
Will my vermiculite and cement board underneath stand the weight?

[SableSprings]

Hey Peter, it occurred to me that if you are going to use a cement board type product underneath your vermicrete layer as a permanent (non-removable form base), simply cut the board 1-2 cm larger on the sides you intend to put tile or protection. That little extension would help you put the vertical form boards in place and after the vermicrete pour sets and the form sides are removed, you'd have a nice little shelf on which your tiles would get the base support they need to stay put without stressing the thinset/vermicrete bond layer.

I think I'd still put the folded metal lath in place on the sides between the vermicrete and tile as extra strength and adhesion for the thinset. I hope that this makes sense to you...I can see it in my head, but...

As a side note, David S recommends putting a few holes in the base material holding the vermicrete. In this case, 4-5 drill holes in the cement board. He does this on his ovens to allow any moisture that accumulates (or that gets trapped) to escape more easily.

[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

[Odin]

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

[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]

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]

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]

[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?

[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]

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.