2024 Neapolitan oven build

[rsandler]

At least from the outside, that looks like very neat work on those last courses, especially with having to dispense with the IT. Nicely done!

I would just make a 2-brick keystone; on my first oven I actually made a 3-brick sandwich. Up to you of course, and if you enjoy the work enough to make half-height bricks to bevel, certainly go for it. Even you will rarely see, much less stare at, the top of the dome, and certainly no one else will. So, do whatever satisfies you at the moment.

[daidensacha]

Keystone, or one more row of bricks.

I mentioned this previously because I foresaw this dilemma coming.

My fire cement finally arrived on Wednesday. I immediately did one more row of bricks, and I had to cut a lot individually as my calculation for the cuts with mr Chipsters jig were a little off, and I wanted the fitting to be as close to perfect as possible. Bear in mind, being a Neapolitan build, I adjust and reset the IT for each course to account for the changing height of the dome and angle of the bricks. It was very straight forward initially, but the last rows became more tricky to keep the small gaps I have been making.

Wednesday night at 2am, my mind was working on how to improve my setup for cutting more precisely. Yesterday in the morning, I took measurements of the hole diameter, and brick angle for the last row. Then I knocked up a 3D model in Sketchup to calculate how many bricks, with the size and angles required. It was much more precise, and of all 18 wedges, I needed to cut 3 individually to fit in the row.

The last 2 rows because so cramped for space to work, I removed the IT and put them in by hand, using props cut from a sheet of ply to hold the bricks in place until I got them all in.

Now I’m left with a hole 115mm on the inside of the dome, and 145mm on the outside of the dome.

Option 1. Cement 2 floor bricks together to make one thick enough to match the thickness of the dome, and cut one large keystone to fit the 115-145mm hole.
Option 2. Cut a few bricks to reduce the width from 64mm to 30 mm, and cut wedges for one more row which would leave a hole 50mm on the inside, and 64mm on the outside. It would be a much smaller keystone, but require a bit more work.

My last 2 rows added by hand without the IT as it became easier due to the lack of space to move the IT.



This was the 3D plan I knocked up for my last row of bricks, as seen above.



This would be my last row of cuts if I decide to add one more row. I would only need 2 bricks cut in half, and 5 wedges from each half. Might just cut them for the exercise. I had considered cementing them together, with the keystone in the center, before test fitting and adding to the dome.

[UtahBeehiver]

Looking good al all fronts

[daidensacha]

Stainless steel reinforcement completed.

I’ve been going stir crazy waiting since 8th to get more fire cement. My supplier, “schamotte-shop.de“ is not being transparent at all, will not answer the phone, only reply slowly to emails and will not give any commitment to when I will receive it. They have been totally unhelpful. I ordered the same product from an alternative supplier who said they could deliver within 3 days. That supplier turned out to be also owned by them, and they sent me 25kg of the wrong product. I now ordered another bag from the second supplier who apologised for sending the wrong product. That should arrive today. I have my fingers crossed that it is correct this time. 2 weeks of good weather have flown by and I have not been able to finish the dome. Very frustrating not being able to work, watching the last good weather for the year disappear.

Here are a few little things I was able to do on the oven. I also finished the terrace paving, started on the terrace gutters, and put a soak well in the front garden to catch the rain water from the roof. Not the jobs I wanted to do, but good to have them done at least.

Stainless Steel Reinforcement
I got my galvanised reinforcing braces back from the engineering shop, so I got into that. The 45° angle on the braces was not perfect for securing my bolts. I bent the stainless threaded rod to fix this, and it works well. Two stainless anchor bolts secure it to the hearth slab, with stainless threaded rod securing each brace across the top of the arch.



Arch Vent Mount
One other little job I managed to get done was to cast a vent mount on top of the arch with a 50/50 mix of fire concrete and vermiculite. It’s strong, level, and my vent cast will fit perfectly on top.

[daidensacha]

Yes, I had to do something similar to the IT

That looks very much like mine now too. I hit it with the 125mm cutting blade to reduce it to 20mm wide today. It should do the trick for the last course.

[UtahBeehiver]

Yes, I had to do something similar to the IT

[daidensacha]

One more course leaves an awkward size hole for the keystone.

New batch of fire cement very different to the first lot I used.
I ordered a 25kg bag of fire cement as I ran out on Tuesday, and the supplier let me down. They didn‘t deliver so I ordered what looks like the same product from an alternative supplier and the bag was delivered yesterday. From the photos, and information provided I expected it to be identical, but it is very different to work with. Very easy and fluid, yet not runny, and grey instead of reddish black. The work time is much longer, and it reacts very differently when in contact with the Schamottsteine. It does not become instantly hard and unworkable when in contact with the Schamottstein like the precious bags. It is more like what I was expecting to start with.

That said, the weather this week has been overcast, cold and wet, with max temp today 13C, min 7C. I did the second last course yesterday, and cleaned it up this morning as the cement is still not set. As the horizontal gap was a bit bigger on this row I inserted slithers of Schamotte in the cement, and much easier with this batch of fire cement.

Anticipated size of Keystone hole to fill: ID 115mm, OD 145mm, is this to big?
As I come closer to the keystone, I‘m presented with an awkward size hole to fill. I have one more course which will leave me with an inner diameter hole of 115mm. On the outside this will be around 145mm diameter. I do have 2 extra 250x250mm floor Shamottestein, which I could use as I would be able to cut them big enough to fill the hole in one piece. I would need to cement one on top of the other as Giovanni Rossi did to make his keystone. I don’t see and alternative, other than to do one more course, which would require me to cut the width down from 64 to 40-50mm to allow a very small hole to insert a small keystone.

I‘m open to feedback, or suggestions if anyone has some experience with such an issue.

Adjusting width of IT brick holding plate as the bricks reduce in width.
One other small issue I didn‘t anticipate was the 50mm wide holding plate on my IT. It was too wide from this last couple or rows of bricks, so I was positioning my bricks to the side so it didn‘t impede the positioning of the brick, This messed with my angles though, and I only realised when finishing this last course that I need to cut the width down to 20mm so I can position the bricks on center, and this should do away with the problems I had these last courses of the angles. It’s ok, as I individually cut one side of each brick as I test fitted it to see what adjustment I needed to make. But I could have avoided this altogether had I realised earlier that I needed to reduce the width of the IT brick holding plate. Hopefully documenting this helps someone else if they encounter the same issue.

[daidensacha]

MarkJerling, UtahBeehiver

Thank you for your kind words, it means a lot given your status as experienced builders.

It’s been on my bucket list for 10 years now, since I first obtained the Forno Bravo plans those years ago. This last year I dove into Sketchup drawing and refining details, working out how I would do it. There is no experience like actually doing it though, and I gained a deep respect for all those who have done it. It’s hard work, working through problems and issues. I’m so glad I spent the last year working out details, and planning. Honestly, it would have been a disaster had I not. So far, it’s falling into place, and I’m trying to balance enjoying the process with the desire to finish it now. The two kind of work against each other, and I’m now leaning more to enjoying the process and it will be finished when its finished.

[Giovanni Rossi]

As others have stated, great masonry!

nlinva referenced my keystone is made of 2 standard firebrick. I just buttered them with a thin layer of mortar and clamped them overnight. A round keystone would have been fine, but I decided to try making a 12 sided one. I'm not sure which shape would have been easier because I had only an angle grinder to work with.

One point to share was that I trimmed and dry fitted the stone a number of times and settled on it resting about 1/4" below the last course. I could have trimmed it a bit more. I was surprised how much room the mortar took up and had to push it out and remove mortar 2 or 3 times. You can see that the joint it pretty tight. It took a bit more persuasion by my wife from above with a rubber mallet than I would have liked to get it in place. But, it sure "locked" everything together.

[UtahBeehiver]

Plus one of Mark's comment. For not being a pro mason, one would never know, a labor of love.

[MarkJerling]

Coming along beautifully. That's a work of art! Well done.

[daidensacha]

Dome taking shape, 3 courses to go.

Despite the threat of rain, and the occasional sprinkle, I managed to get another row of bricks done. I reduced the size to 1/3 brick, and they fitted much better than I think 1/2 bricks would have. I got to say that I’m really happy David advocated for using a wet cutting saw over a grinder with masonry blade. I still had occasion to use the 125mm grinder at times, but not a lot. When I did it was super dusty and dirty. Using the wet cutting saw with mr Chipsters jig saves a lot of time and mess.

I’m now used to walking around the outside of the dome to lay bricks, and gotten used to playing the bricks with near vertical horizontal joints. With a slightly more fluid mix it with the brick positioned with the IT, I’m able to fully fill the joint with cement as it easily flows in. I need to let it sit a minute for the cement to set a bit, then remove the IT while holding the brick and at the same time positioning a cut prop under it to hold it up while it sets so it doesn’t move or fall.

It’s time consuming given it’s not my profession. This last course yesterday took me 5 hours to set up mr Chipsters jig for the cuts, cut the bricks, to lay them, and then to clean up.

Overall, with help of my dome shape template that I cross check with for each course, the Neapolitan shape is going to plan.

[david s]

Ok. It is a technique which gives greater stability and control, used for bracing kilns where the expansion issues are around double what we experience with our ovens, but the same principles apply. For kilns the rods and nuts are usually exposed which allows access for adjustments before, during and after firings.

[daidensacha]

Using two threaded rods gives the brackets far more stability as shown (one pushing the other pulling). With your brick gallery you may not have enough room to do this though.

I’m not to worried about it, as the tension of the reinforcing straps will be pulling he upright brackets outwards, while the threaded rod across the top will secure them from moving outwardly. The other thing is, on the threaded rod, I plan to put double nuts on the inside and outside of the angle to lock the angles at 90 degrees.

The Brackets are 50x50x5mm steel angle, professionally welded in a precision engineering factory, which will make them really rigid and resistant to twisting once they are anchored with 10mm stainless concrete anchors.

[daidensacha]

There are definitely examples of people mortaring bricks together to serve as keystone.

A vertical mortar joint can be seen, for example, in Giovanni Rossi's build (post 54 here).

Other people have also done horizontal mortar joints, which is what I'm about to try doing. Two of my bricks stacked flat on top of each other are only about 1/4" taller than the width of the brick, so the keystone will stick out above the rest of the dome by about that amount, which I'm fine with. It does give you the full flat area of a brick to serve as the keystone, which I like. If I decide that 1/4" bothers me, I may just grind a bit off the top with my angle grinder before dropping it in.

Right now I'm thinking about how best to mark and measure the shape of the opening so I can transfer it to the bricks. It is not so hard to transfer the bottom shape to the bottom of the keystone, but the challenge is to mark off the top so that not only is the orientation the same, but also the centerpoints line up. Are there tried-and-true tricks for this?

Thanks, I guess I’ll look at it when I’m there and make a decision then. Really depends on how big the keystone will need to be as to what I will choose to do.

With some of my more tricky cuts where I felt it was really important to have it fitting well, I made templates from cardboard. Easy to cut with scissors, and easy to start fresh if I cut too much off. Worked well for me.