2024 Neapolitan oven build

[daidensacha]

What mortar to build up bricks around outer arch vent and chimney?

I have a question about the construction of my chimney, mainly what type of mortar to use for the bricks surrounding the insulated vent and flue.

I have a pallet of historical hand made clay bricks that I am planning to use to build up the form around the chimney. I cast my own vent out of fire resistant concrete, which will sit on top of the arch vent. Schamott adaptor plate with 2 x 300mm long flue sections will sit on that.

I plant to wrap the cast vent, with schamotte flue with fire blanket, then to brick up around it leaving space between the fire blanket and bricks. I could either leave that space, or fill it with loose vermiculite. I explain this because I don’t see the surrounding bricks being exposed to high temperatures, and think I can use normal cement mortar to build up the bricks.

I do need to build up a flat section on the arch for the cast to sit on. I had planned on using firebricks, but am now wondering if it could be worth considering homebrew vermicrete (5/1 mix)? Vermicrete would reduce heat conduction up into the brickwork above the vent area.

Image of my planned chimney, along with the cast vent with schamott adaptor and 1 x flue that will sit above the oven arch vent.

[UtahBeehiver]

Not disappointed, very impressive timber works.

[daidensacha]

The big C variant seems to making the rounds, several friend and family have gotten it. Glad you are on the mend. Your brick work is really nice quality and top notch, expecting to see something similar with you timber works.

Thank you for your kind words.

I cut all the timber at the workshop of a family connection, as it was all so big. Longest lengths were 9.8 meters, with main front beam 200x100mm around 100kg. The rafters @ 200x80x5400mm were much lighter, but still a two man lift on the ground. It was much easier to cut all the joints and pre drill holes, fit locking plates prior to moving here and building it up. 2 days cutting and fitting, 1 day painting with transparent white oil, and half a day to put it up with help from family. 5 of us to lift and move it all into place. Brother in law brought his tractor with the forks on the back to lift the main beam up so we could settle it on the posts. That was the hardest part, but it went well.

Some pictures of the cutting and fitting.



The timber in place above the oven ready now for the sheeting.

The paving is 9 x 5 meters, with the roof 9.8 x 5.4 meters having 400mm overhang. It’s 3.5 meters high where it attaches to the wall, and 3.1 meters high at the front of the terrace. I did the plans myself in sketchup, using nice solid laminated pine timbers. Posts are 160x160x3000mm. Am using insulated sandwich sheets for the roof.



The balconies on the side of the house will be extended 2 meters, with a staircase allowing us easily to walk down to the rear terrace, pizza oven and garden. I’m running out of time to do that now this summer, so it will happen in the beginning of next spring. Now focussing on finishing the oven and rear terrace.

[UtahBeehiver]

The big C variant seems to making the rounds, several friend and family have gotten it. Glad you are on the mend. Your brick work is really nice quality and top notch, expecting to see something similar with you timber works.

[daidensacha]

Outer Arch progress

Timber was delivered on the 14th, so that week became prioritised for building and putting up the timber framework for the terrace that will be over the oven. Roof sheets will be delivered mid Sept, so wanted to finish that and get back to the oven to do as much as possible before the roof sheets come. Ideally would like the chimney done so I am ready to cut the hole in the roof to install the double walled flue. That took me from 14-17 August.

Then back to the oven, and I decided to complete the front arch before starting on the dome bricks above the soldiers. Like the inner arch, I found the inner arch pretty straight forward and surprisingly easy to lay the bricks. I can only hope I find the dome bricks are as easy to lay.

I put a piece of 10mm ply in-between the rear and front arch to maintain a consistent gap in which I can insert the ceramic fibre covered with homebrew 5/1 vermicrete. It worked perfectly. I’m also happy the vent is exactly the size I planned on in sketchup, so my homemade vent cast will fit perfectly on top.

I knocked up an adjustable jig for the wet cutting saw so I can cut the top and bottom angles on the dome bricks. My first four courses above the soldiers are crucial to setting the curve of the Neapolitan dome. I tested my homemade jig for cutting the left and right sides of the dome course bricks, and it works perfectly. Photos to come.

I am planning on fitting the steel angle braces that will secure the stainless steel straps around the soldier course. I will update more info on this soon.

I tested positive for COVID this week, and it knocked me for six. Been layed up since Wednesday unable to do anything on the oven, but back on the computer today planning. Hope to be back on the dome tomorrow, will see how my energy levels go.

[daidensacha]

Inner arch

I removed the form from the inner arch this morning between showers. Amazing how the mortar drying process differs in cooler weather. 20C yesterday when I did the arch in the morning, and in mortar was still wet at night time. This morning set like rock.

I watched to remove the form to clean up the inner face of the arch, and point up any voids in between the bricks. Glad I didn‘t leave it as it was a bugger to chip away off the bricks. It cleaned up well. Quite happy with the result.

[daidensacha]

Soldier course and inner arch

I laid out the soldier course full bricks to see how they fit, and how many were needed. 40 bricks in total. I was actually surprised how they sit on the insulation layer, very sturdy and not as slippery as I had feared. It was my major concern with the weight of the dome sitting on top that they would slip and blow out.

I decided on using the full bricks for the soldier course, confident that with the bond of the cement joining them, and the stainless steel strap that will go around them to reinforce the lower course will be sufficient. Additionally, with layers of insulation outside the dome (ceramic fiber blanket, and 20cm of vermiculite/perlite homebrew) I‘m pretty confident it will hold.

I cut a 12mm heat break in the floor between the outside of the inner arch and the vent gallery. I cut a 12 mm ply profile to keep the gap correct until I fill it with 13mm ceramic fibre blanket topped off with 5/1 vermicrete.

To the brick laying. It was 30 degrees, and I soaked the bricks for a good 40 minutes until they stopped bubbling before taking them out of the water for the surface to dry off a bit before laying. Man, it was not easy, and definitely have a new found respect for those who build their own oven. It took me a good 5 hours, laying, relaying, relaying, relaying until I was happy with the positioning of the bricks, and that the mortar bond was good with the bricks.

I read a lot about how the bricks suck the water out of the mortar, as at 30 degrees it was instant when I put the bricks together. Even with wet bricks. I suspect my buttering was not perfect, and I just kept repeating until I got it done.

Saturday I cut the inner arch bricks with the wet cutting saw, to my specs from my design in sketchup. Fitting them then on my template to make sure they fit with sufficient gap for mortar.

We had 2 days of non stop rain, and my bricks sat out in it. I figured it wouldn‘t hurt, and might in fact help when I come to lay them. This morning, overcast with no rain, cooler weather, so got out early to do the arch. Making use of cooler weather and no rain. I made small batches of mortar, and my buttering was much better. Positioning the bricks precisely and moving them into place within seconds before the water disappeared worked much better than when I laid the soldiers. It was very quick, done in a few hours.

I know some might ask or suggest that I use full bricks for the sides of the arch. Actually the inner bricks directly under the arch are 114mm wide, but also 140mm long so I could cut the inside face to the shape of the inner dome. Had I used a brick width wise, I would have needed to cut a small piece to fit inside, and I didn‘t want to do it that way.

[david s]

Thank you, that’s really helpful info for my application. I was curious how you used stainless steel. Could also use stainless U-profile with ceramic fibre board under it. Then the ceramic fibre board could also fit inside the U-profile. That sounds like a good solution to me.

The stainless might look pretty, but it is a poor solution as an insulator. The thicker the wall thickness of the tube, the more heat it will conduct and transfer across the gap. While stainless is less conductive than mild steel, it is still many times more conductive than firebrick. So if you want to replace firebrick with a material that insulates then a highly conductive material is not particularly effective. As the gap’s primary function is to act as an expansion joint. Filling it with a square tube will not provide any flexibility. Perhaps a thin (0.5mm) u shaped tube might have sufficient flex to accomodate the expansion. Filling it with blanket would be better than just air.

My solution is to fill the gap with blanket to within 5mm from the top and fill that last bit with 5:1 vermicrete which is somewhat flexible and seals away any ceramic fibres. In my design it’s too hot for high temperature silicone to work there. Other fireproof caulks I’ve tried just go hard and fall out.

[Toiletman]

Marking the floor bricks the right way.

Yesterday I used a ply template I made to mark the cuts for the floor bricks. Then this morning I removed the center floor brick, did some calculations to work out the height I wanted the indispensable tool to be mounted. I cut a 20mm piece of water resistent ply to replace the center fire brick and mounted the indispensable tool. After I place it in the middle of the oven floor, I checked the cut lines with the IT, and discovered they didn‘t line up exactly. Oops.

I erased the incorrect lines, and remarked the correct floor diameter with the IT. Then I cut the bricks using the wet cutting saw. At the end of the day I cleaned the saw, and I was surprised at the firebrick sludge that had settled in the bottom of the saw water reserve. Can I use this sludge perhaps under the floor bricks to level them?

On the marking: good job on the check twice before cutting... I also made a measuring oops today and also cut it... luckily I made the cut too large, instead of too small

For the sludge: I think this is what could then be sold/used as fireclay if I understand the comments here correctly (after sieving very finely, and drying). I wouldn't use it wet on calciumsilicate due to its dislike for water (the calciumsilicate becomes 'pulpy'). If you have some kind of waterproof layer or the waterproof insulation material you might consider using it wet.
After the layer became too large I took it out with a bucket, I'm up to two buckets by now, but they take ages to dry... not sure if I'll do anything with it or in the end it will just go to the construction trash section of the recycling center.

[daidensacha]

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.

Thank you, that’s really helpful info for my application. I was curious how you used stainless steel. Could also use stainless U-profile with ceramic fibre board under it. Then the ceramic fibre board could also fit inside the U-profile. That sounds like a good solution to me.

[daidensacha]

Marking the floor bricks the right way.

Yesterday I used a ply template I made to mark the cuts for the floor bricks. Then this morning I removed the center floor brick, did some calculations to work out the height I wanted the indispensable tool to be mounted. I cut a 20mm piece of water resistent ply to replace the center fire brick and mounted the indispensable tool. After I place it in the middle of the oven floor, I checked the cut lines with the IT, and discovered they didn‘t line up exactly. Oops.

I erased the incorrect lines, and remarked the correct floor diameter with the IT. Then I cut the bricks using the wet cutting saw. At the end of the day I cleaned the saw, and I was surprised at the firebrick sludge that had settled in the bottom of the saw water reserve. Can I use this sludge perhaps under the floor bricks to level them? I would just need to sieve out the pieces of firebrick so I can have the fine sludge, but it seems to settle and takes work to break it up.

h

[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.