2024 Neapolitan oven build

[daidensacha]

Jobs for the week

I had my first day off today since I can‘t remember . I covered the oven with tarps last night as the render over the concrete brickwork was drying much slower than that over the old recycled clay bricks. This morning its stiffened up nicely, as it stayed reasonably a warm 12C overnight.

My main task this week is to insulate the dome with ceramic fibre blanket and the first layer of V-P-Crete. I‘ve listed a bunch of other tasks to do when I have spare time.

1. Cover dome with 100mm of ceramic fibre blanket.
2. Fill chimney and sides of arch with Perlite.
3. Mix and cover dome with 35mm of homebrew V-P-Crete.
4. Oak doors: Need to refit one hinge so the doors fit squarely together when closed. Have a little repair work to do on the render around a few hinges.
5. Tile under granite landing.
6. Add final layer of render over the chimney and arch frontage.
7. FIt gutter and downpipe for terrace roof (sheets hopefully delivered end of next week)
8. Fit light on front of oven above arch when render is dry enough.
9. Fit light switch, and connect wires to light and mains. (not connecting into the mains until I have the roof on)

I‘m excited that I begin to see a light at the end of the construction phase. So happy that I cut my last bricks as my hands showing signs of the work they have done. I applied for a new passport a week ago, and had no fingerprints left, haha. I explained I have been building a pizza oven and that the stones are like sandpaper. What to do….

My todo‘s:

1. Measure and order granite for the work benchtop once the oven is rendered and I can be sure of the exact measurements.
2. Source a nice slice of an oak tree truck for the bar at the back of the work benchtop.
3. Order double walled stainless steel flue for extending the flue up through the roof.
4. Add crown on the chimney once the flue extension is done.

[nlinva]

Yes, I have the same fingerprint issue. My computer, which I can normally wake up from sleep with my finger, no longer recognizes it. :-)

[david s]

Building the oven has introduced me to things I never considered before. Heat movement for example, as explained very clearly by david s early on when explaining the function of the heat break. Heat loss through convection and conduction are to be considered.

A double walled stainless steel flue has 30mm of insulation in it, so my reasoning without going into it scientifically like you, was that 35mm (1.5“) would be sufficient around the flue. The reason I want to fill the remaining void is to prevent/limit the walls heating. Hence I wanted to fill the void to prevent the transfer of heat via convection though the air. I thought that would be more than conduction through dry Perlite filling the empty space.

A question arose reading your chart, where your top end temperature range is 300C. Is that a realistic possibility, that the flue gets that hot? I thought it would be less, given it’s not exposed to the direct fire, only the. exiting smoke.
[/QUOTE]


Regarding the perlite vs air comparison, as well as the perlite eliminating air flow in the space, it also introduces a barrier for radiant heat. On pondering this I remembered an innovation used in window double glazing of windows where the space could be filled with loose insulation (I think it was polystyrene beads which were pumped into the space when required, or pumped out if views were preferred.
Regarding K values, they are the reciprocal of R values. There are many different units used for insulation value, which makes things confusing. Time is also an important factor, sometimes not included.
Thinking about your problem last night when I was firing one of my ovens, one with a double flue (5”/6”), the outer pipe after one hour of firing, I could hold my hand against the outer pipe for about 2 secs. After 2 hrs only 1 sec.
You should get better insulation with yours because the usual set up with a double flue is a one inch space rather than mine of only 1/2”, which was also just air and not filled with any type of insulation.

[daidensacha]

Oven Insulation Started

I guess to much is better than not enough. When I ordered everything for my oven back before spring, I did some calculations and ordered 3 x 7.4m x 610mm x 25mm rolls of ceramic fibre blanket. Then I saw an offer a month ago and ordered 1 x 14m x 610mm x 13mm roll to use in the vent and chimney. I had about half the roll left when I finished insulating around the vent and flue in the chimney, and I filled the chimney from the arch up to over the vent.

So yesterday I got stuck into covering the dome with ceramic fibre blanket. After covering the dome with 4 layers, I had lots left over. So I added another 2 layers on top of the dome. It now has 100mm around the sides, and 150mm on the top, with about 200mm over dome where it meets the chimney. It wasn‘t planned to have so much, and maybe it’s overkill, but better than having it sitting in my garage and not using it. I covered it with a layer of chook wire, with screws into the calcium silicate under the dome to hold the wire.

In the afternoon I refitted one of the hinges for the doors, and they now fit flush with the door jam under also fitting. I need to patch some of the render around the hinges, and the door jam, but I‘ll do that when adding the final layer of render on the chimney.

Today I started on the first layer of homebrew v-p-crete.

Recipe: (parts

1. 5 parts Vermiculite
2. 5 parts Perlite
3. 1 part cement
4. 1 generous handful of clay powder per 1 liter of cement
5. Water to mix by hand into the right consistency.

I‘m no expert and my experience with this recipe is limited. The clay powder seems to make it easier to work with, besides making the mix a nice brown color. Theres a knack to adding it, and I got that pretty quick. Scoop up enough to fill both hands, then plonk it in place against the dome with one hand holding it against the dome, and the other patting it down flat on top. Adding horizontal layers one at a time until it curves over and on top of the dome. Then I poured a bucket load on top, spread it out, and patted it down to around 35mm thick. Possibly a little more in places. When finished, I scraped back the high points, and filled the low points to get s somewhat even shape over the dome. I put a vent in the top as well. A hydraulic vent (as described in the Forno Bravo forum) screwed into water pipe. It sits on the ceramic fibre blanket, and will give me peace of mind knowing if there is for whatever reason a buildup of pressure in between the dome and outer render then it has a release.

Now the wait for it to dry so I can do the next layer.


.

[david s]

With so much insulation blanket the insulation value of your p/v crete doesn’t matter much, so it’s primary function is just to restore an even shape and surface for a final render/stucco. Once it has set and dried a bit (usually around 24 hrs you can carve back any high spots and fill any low spots with the same mix. After covering the whole thing, simply tapping the surface with a trowel produces a very good surface to provide a suitable substrate for the render coat (after drying and drying fires).

[daidensacha]

With so much insulation blanket the insulation value of your p/v crete doesn’t matter much, so it’s primary function is just to restore an even shape and surface for a final render/stucco. Once it has set and dried a bit (usually around 24 hrs you can carve back any high spots and fill any low spots with the same mix. After covering the whole thing, simply tapping the surface with a trowel produces a very good surface to provide a suitable substrate for the render coat (after drying and drying fires).

That’s good to know. My next coat will primarily be to make the sides flush with the stand, and to form a good shape with nice curves. Looking forward to it.

Looking like I’ll have about 400 litres of Perlite and vermiculite for the garden. It’ll be really good for my vege garden.

Also looking forward to the drying fires, but I’ll sort my terrace roof and flue first.

[daidensacha]

V-P-Crete one day on, drying nicely.

I was shocked this morning when I went out and inspected the v-p-crete that I put on the dome yesterday. The outer layer dried overnight with no sign of water, although there is for sure water under the outer surface. To the touch it felt a little soft and crumbly, so I let it be. Tonight when I packed up and covered it again, it had set much harder. To the touch it feels solid, like one hard mass. I‘m really impressed.

I already scraped it back to an acceptable shape yesterday, so letting it be now, but will follow david s tips when I do the final layer. I thought you (david) made a typo when you said “tapping the surface“, but I clicked a few moments ago and got what you mean. I tried troweling it yesterday but it wasn‘t stable enough with the blanket under it. I did put my hands on it with a little pressure to compact it as much as I could. With the final layer I‘ll use my trowel to lightly tap it to create a surface that I can add the mortar on.

Added tiles, door lock and handle.

I did a little tiling under the landing this morning. Hand made Italian tiles. Will add the grout in a day or two.

With my doors now in place, I fitted an inside lock on one door, and an old style door handle.

[daidensacha]

While waiting for v-p-crete to dry, refer to todo list and finish off odd jobs.

Today was 19C, sunny with blue sky and perfect weather to help the drying of the v-p-crete layer. If I wait a full week, then next Monday or Tuesday will be my next layer.

So I referred to my todo list, odd jobs and details to be finished.

1. I grouted the tiles, dark grey to match the granite and super happy with how it is looking.
2. Cleaned out around the render around the hinges in preparation for patching it up.
3. Filled the chimney space around the flue with perlite.
4. Swept off the loose v-p-crete pieces on the dome, leaving a nice hard shell that has set really well.
5. Prepared my gutter hooks for installation tomorrow, weather permitting. Could be a little rain in the afternoon.

[david s]

Looking very nice. Slow and steady wins the race. Wonderful attention to all details.

[david s]

This is a useful tool. A simple cheap garden moisture meter can indicate when the p/vcrete layer is dry.

[daidensacha]

This is a useful tool. A simple cheap garden moisture meter can indicate when the p/vcrete layer is dry.

I have one in my garage, somewhere. I’ll have a look for it, out of curiosity to check what reading it gives.

That said, yesterday was the first day I fully uncovered the oven for a few weeks. There was a lot of condensation inside the tarps. Although the chimney render is dry and hard, I can see brick shapes in it from moisture exiting, so I know the best thing to do is be patient and let it dry out.

When I knock on the v-p-Crete it’s sounds hollow like a hard shell. I know the ceramic fibre blanket would have also absorbed moisture.

I’ll wait till Tuesday (1week since adding) and check the moisture content then.

[daidensacha]

Second and final layer of v-p-crete

The weather today was perfect, given it‘s coming into winter. 17C max, blue sky and sunshine the whole day. WIth some afternoon rain forecast for tomorrow, and a cold change in about a weeks time, I was out at 8.30am mixing v-p-crete to put the final layer. I did find my ph/moisture probe and tested the v-p-crete 3-4 days ago, and it was dry, or so the probe said. But I decided to wait a week before proceeding to be sure.

I‘m trying to find a balance with completing what I can while the weather is still allowing it, and pondering delaying work until next year if the weather doesn‘t allow me to finish.

With the final layer of v-p-crete insulation completed, I‘ll leave it for a week to dry before re-assessing my next steps.

I‘ve been researching double walled stainless steel flue, and what parts I need to extend the flue from the chimney through the new roof when its on. I‘ll order it tomorrow or rather next day. I need to consult with a chimney sweep, as its required by law in Germany that all flues that go through a roof are cleaned and maintained by a registered chimney sweep.

I want to start my drying fires soon, now the final layer of v-p-crete is on. The weather is getting colder next week, with max: 9-10C, min: 2-6C. I wont be able to rely on sunshine or warm days, although keeping fingers crossed some might still come.

I do have a question regarding the drying fires. Is it better to do them before adding the final render? With the weather, I need to know this to plan on whether to delay or wait for a day warm enough for it to set.

[daidensacha]

Before and after insulation images.

I thought it’s interesting to see the before and after images to get a perspective of how much insulation is on the oven.

[david s]

Moisture driven out by fire and trapped in the insulation layers (blanket and p/vcrete) has a much better chance of finding its way into the atmosphere if it’s not held back by a hard rendered shell on the outside. Coupled with the assistance of sun and wind to dry the outer surface at the same time, so yes, the drying fires are best done before final render coats.
This then creates a problem of applying the outer render to a dry surface. My remedy for this is to cover the whole oven with clingwrap after completing the outer render so moisture is then retained in that layer for a week. Considerable strength improvement is achieved if it’s damp cured for a week.

[daidensacha]

Moisture driven out by fire and trapped in the insulation layers (blanket and p/vcrete) has a much better chance of finding its way into the atmosphere if it’s not held back by a hard rendered shell on the outside. Coupled with the assistance of sun and wind to dry the outer surface at the same time, so yes, the drying fires are best done before final render coats.
This then creates a problem of applying the outer render to a dry surface. My remedy for this is to cover the whole oven with clingwrap after completing the outer render so moisture is then retained in that layer for a week. Considerable strength improvement is achieved if it’s damp cured for a week.

I‘m just so impressed by how hard and how quickly the v-p-crete sets. I cover it at night to prevent it getting added moisture from dew, and go out to uncover it first thing so it can dry out throughout the day. This morning I was pleasantly surprised to find the surface of the v-p-crete dry, and by days end it became really hard. When mixing it, it is hard to imaging how solid it becomes. Looking forward to the next stage of drying fires.