2024 Neapolitan oven build

[Toiletman]

Giovanni Rossi

Thanks Giovanni. My first idea was to just fill the gap with rope. I checked out Mongo‘s solution, and it looks interesting. Today I bought some ceramic fibre blanket, 13mm thick which I will cut to fill the gap. I can add rope along the inside of the arch, with firebrick mortar over it, or same without the rope. I will put the 12mm gap in the floor as well.

This was the ceramic fibre blanket. Left over will be used and not wasted.

Instead of using mortar you can consider putting high temperature silicone: it will flex with the expansion differential between chimney and dome, instead of the mortar which will probably crack. I've been trying to find a recommendation for a European brand, but haven't found one yet. You do want to make sure to have sth in between ceramic fires and your food area.

PS: my gap is 1", fitted with a 1" stainless steel square tube. Stainless steel: low thermal conductivity, doesn't rust in the rain/moisture that it will inevitably see. Aluminium conducts heat very well, so I didn't consider it for a heat break material. As my bricks are around 2", the other 1" was nicely fit with a piece of calcium silicate (1" thick). Thinking about it now I should've filled the tube with vermiculite, as it's large enough to allow circulation to exist inside... but alas...I'm not going to drill a hole in it now to try to get it to flow in.

PS: it would have probably been just fine to put loose vermiculite under your heat break tube, if you close it in from the sides with some tape or cardboard until your bricks are in.

[daidensacha]

Giovanni Rossi

Thanks Giovanni. My first idea was to just fill the gap with rope. I checked out Mongo‘s solution, and it looks interesting. Today I bought some ceramic fibre blanket, 13mm thick which I will cut to fill the gap. I can add rope along the inside of the arch, with firebrick mortar over it, or same without the rope. I will put the 12mm gap in the floor as well.

This was the ceramic fibre blanket. Left over will be used and not wasted.

[daidensacha]

You should have a gap at the floor (your floor bricks will conduct heat too). 1/2" is pretty wide, but you can just fill with cardboard or something similarly flammable to keep the space, which will in due course be replaced by ash, which is a reasonable insulator. Or you can leave an air gap, which will again end up filled with ash in due course. I think on my first oven I did cardboard, and on the second did 3-6mm of Nomex felt, which didn't come all the way up to the floor level, so the rest filled with ash.

Thanks, yes I decided on adding the heat break in the floor. 12mm is a lot if I was to leave it to fill with ash, but I wanted to add insulation. My first thought was rope insulation, and I was considering vermiculite/ perlite homebrew, but I bought some ceramic fiber mat today. I was relatively cheap for a 2000 x 600 x 13mm sheet. I can cut it down to leave space inside the arch to fill with firebrick mortar.

I will go with my 12mm gap between the inner and outer arch, filled with ceramic fibre blanket, covered over with firebrick mortar. I will reduce heat conduction between the inner arch and the gallery outer arch. I can use the excess blanket around my flue above the vent.

[Giovanni Rossi]

daidensacha I seem to recall someone wanting to us a lean vermiculite or perlite mix to fill the gap and there was a recommendation to use a refractory concrete mix (heatstop?) instead of portland cement.

Obviously you'll want to isolate from your cooking space any kind of ceramic fiber product if you use one.

I know you're asking about a floor gap, but I assume you'll also be using a heat break at your arch. Take a look at Mongo's build. His break is my favorite. Had I decided to build my oven from scratch, I was going to emulate his technique.

Back to the floor. I'm not sure I've seen it, but Mongo's arch concept could be applied there using a gapped half lap joint with an insulator or just leaving an air space.

[rsandler]

You should have a gap at the floor (your floor bricks will conduct heat too). 1/2" is pretty wide, but you can just fill with cardboard or something similarly flammable to keep the space, which will in due course be replaced by ash, which is a reasonable insulator. Or you can leave an air gap, which will again end up filled with ash in due course. I think on my first oven I did cardboard, and on the second did 3-6mm of Nomex felt, which didn't come all the way up to the floor level, so the rest filled with ash.

[daidensacha]

Heat break filling

Toiletman last post made me aware I need to work out some issues around my heat break. I need to consider and plan now to save limiting my options when I come to integrating it.

I planned for a 12mm/ 1/2“ heat break directly after the inner arch. Illustrated in the image with blue.



What I didn‘t fully nail down yet was if I also include it in the floor, what to use to fill the gap, and how to seal it at the floor level.

I‘m curious what other have used, and recommend.

I have ample vermiculite and perlite for over the oven, so I could make up a brew to fill the space.
I could also get some 13mm ceramic fibre blanket to insert in the space when building the outer arch.
I saw mention of using stainless steel, but i‘m not sure how that is used, and implemented. Is it worth considering?

With regard to sealing the gap, I was thinking that using fireclay mortar to cover the inserted insulation, maybe the last 10mm of the gap.

I would definitely be simpler and save me extra work to cut the break in the floor bricks now while laying the floor.

[daidensacha]

You were going to build your dome directly onto the floor bricks right?

I made the template for marking the flooor brick cuts so they lay within the oven dome and arch. The dome and arch will sit directly on the calcium silicate sheets.

I allowed for 3mm gap between oven floor and dome wall. A 2mm gap between gallery floor and arch wall. I’m still undecided if I will include my heat break in the gallery floor.

Once my floor is cut to shape, I’ll repurpose my ply floor template by cutting it in half, and lay it over my floor during the dome build for protection. It should also allow for more even weight distribution should I need to stand of the floor. It will also catch any mortar spill, keeping the floor nice and clean. Just need to cut it so I can get the pieces out through the arch when the dome is up.

[Toiletman]

You were going to build your dome directly onto the floor bricks right?

After finishing the dome, I replaced some ugly cut bricks in my gallery floor. To do that I had to take em all out, so I also re-leveled them (all my floor tiles have a (dry) clay/sand mix underneath them). In doing that I noticed that there's quite a jump from the stainless steel heat break to the floor tiles. This seemed to be significantly higher in the middle (1mm) as to closer to the dome walls (~0mm).
So it seems that my floor tiles were seriously pushed down by the weight of the dome. So if you put sand underneath: ensure you put some heavy load on all of them (ie. your jumping? ) and/or hammer all of them in place. I did this, but apparently not hard enough. In the end however, all of this is fixable with the grinder .

[daidensacha]

If your slab is level and CaSil board is true, unless your bricks aren't uniform, you should be fine. If needed, sort through the bricks to get the best match. You may just need to knock off any high points with a cup grinding wheel and an angle grinder...just use a low speed and go slow.

True, you'll not want to introduce moisture to your CaSil board. I know david s has green-lighted sand only before but cautions making sure the sand is very fine. I've had to sift sand at times for other projects. I just sneak the sieves out of the kitchen when no one is looking.

Thanks Giovanni, I laughed when I read you sneak the sieves out of the kitchen. Mums the word, I did the same yesterday with a bottle brush to clean out some drill holes in my concrete so I could fill them with epoxy.

I did play around with the bricks today when laying them out, and the surface is mostly very flat, luckily, apart from a few small areas that where it is like 1mm higher. I might use a little fine sand there when I lay them in place after cutting tomorrow. Alternatively I do have a concrete grinding cup for my 125mm grinder. I will be using it tomorrow to get the sides on the bricks rounded to shape once cut, so I can get a feel how it works on the refractory bricks. It will only need minimal taken of the joins in a few places.

I still need to make up a wooden block to fit in place of the center brick where I will mount the indispensable tool. Will do that tomorrow as well, once I have the side cuts done.

[daidensacha]

Set calcium silicate board on mosaic sheets, floor bricks marked for cutting

I had a few days away in Süd Tirol this week, needed a break. Before I went I cut the calcium silicate boards so I could get to setting them on the hearth when I returned. Yesterday I drilled out the drainage holes from under the hearth through the inserted pvc conduits added into the hearth concrete. There was only about 8mm above the conduit to drill out, was really easy.

I layed out the mosaic tile sheets to cover the required area for the calcium silicate sheets to sit on, and cut the sheets back a bit to within about 50mm from the sides of the calcium silicate sheets. Then I glued the calcium silicate sheets together on top of the tiles with fire resistant refractory glue.

Today I layed out the refractory floor bricks (250 x 250 x 64mm) on the calcium silicate sheets. I had already made a template the size of the inner floor, so I layed it on the bricks and marked the outline with pencil for cutting tomorrow.

So I was climbing over, standing and walking on the front shelf, even jumping on it. Happy to confirm it‘s strong az!

A few photos.

[Giovanni Rossi]

If your slab is level and CaSil board is true, unless your bricks aren't uniform, you should be fine. If needed, sort through the bricks to get the best match. You may just need to knock off any high points with a cup grinding wheel and an angle grinder...just use a low speed and go slow.

True, you'll not want to introduce moisture to your CaSil board. I know david s has green-lighted sand only before but cautions making sure the sand is very fine. I've had to sift sand at times for other projects. I just sneak the sieves out of the kitchen when no one is looking.

[daidensacha]

Levelling hearth floor bricks on calcium silicate board.

I’m about to layout my floor bricks to mark for cutting, and anticipate I’ll need to use something under them to level them.

In Germany I’m having trouble working out the equivalent material for fireclay. Schamottemörtel is available, which I think is probably it. Fire resistant mortar made from powder from the fire bricks. I read that using a 50/50 mix with sand, then troweling it as when laying tiles is suggested.

It maybe a silly question, but I don‘t want to use it wet on the calcium silicate boards, so can I use it dry?

Secondly, I read that some have used only sand without fireclay. Would this be ok?

[daidensacha]

For clarity, I wasn't advocating to change the arc of the dome, it would would just move up or down with the height of the vertical courses.

BTW, really admire your casting and concrete work.

Thanks Giovanni.

I have some skills with my hands, and learnt lots doing renovations in a few houses in my life. That said, transferring that knowledge and applying it to this project does require a considerable degree of problem solving. I’ve enjoyed it so far, and as hard as it has been on the old body, the physical exercise has been beneficial. My long term back pain has virtually disappeared, like a miracle.

Still lots to do, so I’m focussing on what’s coming and enjoying looking in the rear vision mirror at the result so far. Cut the calcium silicate sheets today, and lots planned this next week to prepare for starting on the dome.

[Giovanni Rossi]

For clarity, I wasn't advocating to change the arc of the dome, it would would just move up or down with the height of the vertical courses.

I get your thinking, though I'm not sure the height differential is all that significant. My oven is similar to your plan at 1067mm ID. I just eyeballed it and, at that size, the first courses of the Pompeii style dome are not far from vertical and give plenty of height at the edge to maximize usable floor space. The only time I really use all of that space is when I bake large batches of bread. When I do that, I have to manage the bake more because the radiant heat from the dome bakes the loaves faster on the sides in close proximity. I find if I bake less and leave a buffer from the walls, I get a much more uniform bake. I'll bet the Neapolitan design would mitigate that problem with dome being lower and providing more uniform heat all around the loaves.

After I sent the reply yesterday, I was thinking about the variance in height and how to fix that. We have fire brick splits here that are used to line fireplaces. They would be 230 x 114 x 32 mm.
Using one course of those and 3 courses of standard with thin mortar joints would pretty much match the height of a soldier course.

Good luck no matter which way you go!

BTW, really admire your casting and concrete work.

[daidensacha]

Giovanni Rossi

Interesting, I’ve been planning my Neapolitan oven for some time, and it wont be limited to pizza, will definitely cook bread and meat in it too.

I was planning on the full soldier course. The refractory bricks I’m using are 230 x 114 x 64 mm. I considered at one point laying courses as you describe, but 4 courses would take the side higher than the soldier course, and then call for a much flatter dome which I didn’t want. Alternatively I could have made the initial straight sides lower but I didn’t want that either. So I’m staying with soldiers, but considering David’s idea to make two half height bricks as described.