2024 Neapolitan oven build

[david s]

The popularity of the hemisphere as a form for brick ovens over the centuries as an all round best performer also relates to its structural integrity as well as its ease of construction. Extreme departure from the hemisphere usually requires either steel bracing or buttressing. Most manufactured cast oven today have much lower domes and higher side walls, because, unlike brick builds with their many mortar courses, they don't suffer from the same structural weakness.
As you've not departed radically from a hemisphere (only 16% lower) I'd expect you won't have problems, so may possibly not need bracing or buttressing.

[daidensacha]

Indispensable tool.

I started this last year, time to finish it in preparation for spring and starting the Neapolitan build.

So I used a castor which was cheap and easy to adapt, with some mild steel rod. One rod inserts into the larger, with a nut spot welded to the tube so I can adjust the length of the arm. Crucial given the curve of the Neapolitan dome. I have to finish welding the bracket on the end, but made it so I can adjust the angel, also needed for this build as I want to set the angle for each course of the bricks so the dome goes to plan.

Its light, sturdy, soon to be finished.

[daidensacha]

rsandler Thanks for your info, I’ll read through it and see if it suits me. I think if I was doing a Tuscan oven which has the same radius for each course, it would probably work for me. With my Neapolitan build, each course has a different radius, and the curve of the dome changes a lot. What I like with the jig I’m working on is that I can set the radius for each course, and on the whole jog pivots from that center point. To the left of the blade for the right cut, to the right of the blade for the left cut, no guess work, super accurate, ……. I hope. I devised a mechanism to lock the bricks in, so they will be secure, as long as I don’t force the cut it theoretically should work well.

Never say never though, will read and assimilate the info in the link. I had a preliminary read, need to nosh it out a bit first.

Update: It’s actually really cool. Definitely like the sideway tilt over the forward tilt. I could calculate my angles quite simply to use it. I’ll update the thread when I have a working jig, and with photos to show which i ended up using.

The dome calculator is new to me too. It is purely for the Tuscan style dome though, going by the calculated dome height when I enter my oven and brick sizes.

[rsandler]

You may also want to have a look at this thread: https://community.fornobravo.com/for...-table?t=16780. You can get the same effect with a jig by just tilting the bricks sideways, rather than tilting forward. Either way works (the dome calculator on the forum has angles for both), but by the top of the dome you end up having to tilt forward quite far to make the require bevel. To each their own, but the side-tilting jig felt safer to me.

[daidensacha]

The chart I created with all needed measurements.

[daidensacha]

I picked up the wet saw yesterday, and gave it a clean and service. Looking forward to using it, will make the cutting so much easier.

A few days ago I searched in the forum for “compound cuts”, just to see what I could find by what others share with their experience of cutting the dome firebrick compound cuts for each course. I was planning on attacking it when I came to it, but found a really cool thread My brick cutting tool.

In it Chris shares the jig he made for making the compound cuts of the dome bricks. It is brilliant, and I’m working on building a jig for the wet saw that will clamp the bricks, holding them at the correct course angle, and cut them according the to correct angle for the course radius. I only needs two measurements, the radius, and the angle of the top of the brick, or alternatively the elevation of the rear of the brick. My plans in sketch up gave me all these measurements. Getting the plan worked out now and started getting materials together to make the jig.

[daidensacha]

david s I never used a set saw, but seen one used and it seems to cut through the firebricks like butter. All my cuts will be through the 64mm height. Funnily, after replying last night I checked “Kleinanzeigen” and a business not for from where I live has 3 they are selling, look almost new, like they bought them for a job and are now selling them.

Comes with 2 x 350mm diamond blades, max cutting depth at 90 degrees: 100mm. I’m going for it, will be handy sitting there when I need it, and I can sell it when I’m finished.

[david s]

Good luck, but remember that as the dome rises the angles to be cut get bigger, so working out the angle for each course becomes really difficult,. It is far easier to just adjust the cuts required as you go.

[daidensacha]

david s I plan to hire a wet saw to do my fire brick cuts, have worked out majority of my cuts, 216 in total, halving bricks, and cutting the arch bricks. It cost me 45 Euro for one day, and should take me 2-3 hours as I’ll make up jigs before hand to make cutting easier.
I need to wait for sprring and the temperature to warm up before I can get to laying my foundation and then hearth, then I can get into the dome. I’m keeping an eye on the German equivalent of Gumtree for used wet saws in the mean time, never know, one might be up for sale at the right price.

[david s]

I should have mentioned that a 125 angle grinder with a diamond blade is totally inadequate for the job as well as being quite dangerous. While the blade is 125mm the depth of cut is far less, only around 20 mm at best. This means the brick needs to be cut on both sides then broken and the rough bit in the middle chamfered off. This is ok and can be done, we’ve all done it for a few, but not if you have hundreds.
The other issue is the danger. Dry cutting of bricks creates very dangerous particles that if inhaled can cause very serious lung disease. This is so problematic that engineered stone, widely used for kitchen benchtops, has been banned in Australia. I certainly don’t want to be responsible for recommending such a dangerous practice via this forum.Unfortunately YouTubers don’t share a similar concern.
A wet saw is mandatory to prevent this dust. Soaking a brick in water then using an angle grinder only stops about half of this dust. It is a danger to you, your family and those in your immediate neighbourhood.
The solution is a wet saw that has a water feed which eliminates all dust and it also gives you a deep and accurate cut. Buying or borrowing one is the best solution because you’ll need it for an extended period. You’d be going backwards and forwards constantly if hiring one.
Many builders bite the bullet, buy one then sell it at the completion of their build. You may be lucky enough to pick up one second hand.

[daidensacha]

attached is an experiment I did for drying a vermicrete slab that helps explain what's going on.

Gone is my ignorance as an excuse. While I have it clear now the order of how to lay the vermiculite if I do decide to do it, I’m not sure I will. Last summer here was an anomaly, lots of sun, usually it is overcast with dark clouds, and really humid. It would take forever to dry the vermiculite layer. even with holes in the hearth and without the dome preventing evaporation. Once the dome is on and the vermiculite covered, I’m not sure how it actually would dry. 1) Vermiculite and Perlite hold the water, water wicks upward, and with the exit 150mm holes in the bottom of the hearth, it kind of goes against the natural flow for the water to get out that way.

Thanks for the info David, looks like I’ll be sticking with the original plan and using just the 100mm Ceramic fibre board. I’ll stick wth the 100mm because the price difference between 75mm and 100mm is minimal.

Delve a little deeper into your block suppliers catalogue. You should find half height blocks, they are commonly used in block work.

I’ll visit my local “Baywa” who supply builders and tradies as I have an account with them and they 1) love Australia, and 2) are super friendly and helpful. Last resort is I can knock up a cutting jig to guide my 125mm angle grinder with diamond blade, a few hours of dirty work wearing a mask.

[david s]

One of several builds I have watched on Youtube that I found really helpful is Wood-Fired Pizza Oven step-by-step in Romania. In it he encloses a vermicrete insulation layer in the hearth, and at 5.22 it shows he puts glass mosaic tiles on the vermicrete before adding the ceramic fibre board. The bottom of his hearth under the vermicrete is very thin although reinforced and with supporting wall under it in the centre of the base. This would be contrary to my question in the previous post re: placing the mosaic layer under the vermicrete.

I would build a thicker base, as I want to include rebar that comes out of the hearth and supports a landing in front of the oven.

Yes this build has that all wrong. Because a basin has been created it is asking for water to accumulate there and there are no drain holes. The tiles should have been placed in the bottom of the basin with the insulation on top..

[david s]

david s I understand you said in your opinion its not necessary to have additional vermiculite insulation on the hearth under 100mm ceramic fibre insulation floor.

In my case, here in Germany we have schalungssteine, which are quite a different format to cinder blocks. I‘m using L500xH250xW175mm (Illustration below.) Aiming for my final height of 1150mm for the floor, it requires cutting the fourth course of blocks down to 136mm. I‘m considering the possibility of eliminating the fourth course altogether, which leave me with 86mm to fill, which I could with a layer of vermiculite/perlite insulation. In the plan below, the hearth is 150mm (100mm above the wall, 50mm inside the wall), so I would need to change that to 150mm above the 750mm wall. It would reduce the height of the space below the hearth from 886mm to 750mm, but would save me on blocks for the fourth course, and the cutting of the blocks.

Above the hearth, it would then be 86mm Vermiculite/perlite insulation, 100mm Ceramic fibre insulation, 64mm firebrick floor, total of 250mm. My floor will be inside the dome first course with the come first course on the ceramic fibre board. (Image below right)

Question: Would also do away with the need to put mosaic tiles? I‘m a bit unclear about the order and structure with this. I see the advantage of putting drainage holes in the hearth, which is straight forward and planned. If I do the vermiculite/perlite layer, is there a way to lay the mosaics under it, perhaps covered with a layer of plastic with holes and then the vermicrete? Or not necessary then at all?

Question: Vermicrete/Perlite mix. For this layer of insulation under the ceramic fibre, what ratio would you recommend so that it is strong enough to support the ceramic fibre and then oven? I considered laying an extra layer of concrete around the vermicrete on top of the hearth to enclose it on the sides. I could do this, or leave it, depending on whether it would be better for support of the vermicrete layer.

Delve a little deeper into your block suppliers catalogue. You should find half height blocks, they are commonly used in block work.

Regarding the layer of vermicrete under a 100mm calcium silicate board I don't believe you'll achieve much because 100mm is already way more than most oven builders would use. The thicker the insulation is the more it suffers from the law of diminishing returns. Additionally the large amount of free water a vermicrete layer contains needs to be removed prior to building over it because moist insulation of any kind does not work very well. We've had reports of oven performance getting better months after completion because that underfloor moisture is difficult to remove. A 100mm cal sit is already dry so this problem is largely removed. However should water get in a space under the insulation created by a layer of tiles with wide spaces and some holes in the supporting slab, do a fine job of allowing moisture to escape. If you have your heart set on doing a vermicrete slab it should be a 5:1 ratio for sufficient strength. The vermicrete over the dome does not support a lot of weight so a !0:1 there is better. (see attached table for strength to insulation relationship). Some weed matting placed over the tiles is enough to prevent the vermicrete from blocking the pathway between the tiles, but enough to let the moisture pass. Also attached is an experiment I did for drying a vermicrete slab that helps explain what's going on.

Vermicrete insulating slab copy.doc.zip

[daidensacha]

One of several builds I have watched on Youtube that I found really helpful is Wood-Fired Pizza Oven step-by-step in Romania. In it he encloses a vermicrete insulation layer in the hearth, and at 5.22 it shows he puts glass mosaic tiles on the vermicrete before adding the ceramic fibre board. The bottom of his hearth under the vermicrete is very thin although reinforced and with supporting wall under it in the centre of the base. This would be contrary to my question in the previous post re: placing the mosaic layer under the vermicrete.

I would build a thicker base, as I want to include rebar that comes out of the hearth and supports a landing in front of the oven.

[daidensacha]

david s I understand you said in your opinion its not necessary to have additional vermiculite insulation on the hearth under 100mm ceramic fibre insulation floor.

In my case, here in Germany we have schalungssteine, which are quite a different format to cinder blocks. I‘m using L500xH250xW175mm (Illustration below.) Aiming for my final height of 1150mm for the floor, it requires cutting the fourth course of blocks down to 136mm. I‘m considering the possibility of eliminating the fourth course altogether, which leave me with 86mm to fill, which I could with a layer of vermiculite/perlite insulation. In the plan below, the hearth is 150mm (100mm above the wall, 50mm inside the wall), so I would need to change that to 150mm above the 750mm wall. It would reduce the height of the space below the hearth from 886mm to 750mm, but would save me on blocks for the fourth course, and the cutting of the blocks.

Above the hearth, it would then be 86mm Vermiculite/perlite insulation, 100mm Ceramic fibre insulation, 64mm firebrick floor, total of 250mm. My floor will be inside the dome first course with the come first course on the ceramic fibre board. (Image below right)

Question: Would also do away with the need to put mosaic tiles? I‘m a bit unclear about the order and structure with this. I see the advantage of putting drainage holes in the hearth, which is straight forward and planned. If I do the vermiculite/perlite layer, is there a way to lay the mosaics under it, perhaps covered with a layer of plastic with holes and then the vermicrete? Or not necessary then at all?

Question: Vermicrete/Perlite mix. For this layer of insulation under the ceramic fibre, what ratio would you recommend so that it is strong enough to support the ceramic fibre and then oven? I considered laying an extra layer of concrete around the vermicrete on top of the hearth to enclose it on the sides. I could do this, or leave it, depending on whether it would be better for support of the vermicrete layer.