42" Neapolitan oven in SW Ohio

[buckeye_brian]

Well...after years and years talking about it, I started the pizza oven. It is a part of a grander outside "MAN-KITCHEN" complete with wood BBQ and stone smoker. This all came to fruition because I could not keep water away from my back walk-out basement door. I decided last spring that I was going to build a retaining wall and pour a slab. This would get the water away from the house. Well we poured the slab on grade on May 1st last year. So for the last 1+ year, myself and my son have been laying brick, block and stone and pouring almost 400-bags of Sakrete concrete whenever we had a few extra minutes.

I will post pictures of how we got to where we are now in future posts, but this is a pizza oven forum, so let's start with they oven.

I layed the stand, poured the insulated base and layed the floor late last summer. Then it sat until last week. My son is traveling now and I have been super busy with other "hobbies." My oldest son is turning 31-yrs old in late August. I asked him 2-weeks ago what he wanted for his birthday. He said, "A pizza from the pizza oven." So that got me motivated to get it done.

I already had bought all materials last year and they were collecting dust in the barn, So far I have layed the inner arch; first course of brick (upright since I am doing a Neapolitan style oven). I have poured the buttress concrete around the base. This is probably overkill, but I wanted to lock in the base course and I had the room. I used a 5-1 perlite with a sand mix concrete. Little stronger but with some insulating value. Finally I have layed a couple of courses. I work in construction and just so happen to have a couple truckloads of sand on one of my jobsites, so I brought some home. Now I have a sand dome in place and ready to start laying coursing when I get home tonight.

As soon as I figure out how to upload pictures in correct format and/or save my pictures so they are not so big, I will post them..

I will keep you up to date as we get closer to pizza making time...

[MarkJerling]

Well done on the progress! I too collected materials for years. It's great to finally get started and then, of course, to get it done!

[buckeye_brian]

Well let's see if I can get some of these pictures to load.

[buckeye_brian]

...and a couple more pics.

I got home last night and layed 2 courses. It is actually easier than I thought it was going to be. The only thing that worries me is building this on top of the sand dome, I cannot clean mortar up and I can't make adjustments. The maddening thing is not knowing what it looks like...hopefully I am not screwing it up too much. The most important thing is it holds heat. Looking good only matters the first month during the guest inspections. After that, they will only want what comes out of the oven instead of how the inside looks.

[buckeye_brian]

I got a little more done over the weekend. I closed in the dome; dugout the sand and layed the front entry arch.

Now I am spending a lot of time looking at the vent and how I am going to do it. The Forno Bravo plans call for a 6" round chimney for 32 - 36" ovens and 8" round chimneys for 42" and bigger. I have an 8' x 8" flue liner. That only measures 6 3/4" side to side. It is 8" corner to corner internal. Is this big enough?

I am building a Neapolitan style oven. My ceiling is only 16'' high and my inner arch height is 12". Not a lot of room to capture heat. I am afraid to make the vent / chimney much bigger than the flue liner. I would think that the bigger it is, the more heat is going to rush out. Any advise on this would be greatly appreciated.

I am also knocking around the idea of placing my chimney on the top center of the dome. I was thinking about cutting a 13" x 13" flue liner in half (lengthways) and making a raceway from the vent to the top of the dome. I watched a guy (on this forum) on Youtube do it and he says it works very well. The problem (or concern) I have is the Neapolitan style flatter top. There is still a good curve and I locked my coursing in pretty well, but I am a little afraid to put a big chimney ontop. Seems like a lot of weight to bring done on a flatter surface.

I poured concrete around the bottom to lock in the first course of dome bricks.

Is my concern warranted or should this not be an issue?

[UtahBeehiver]

Too small of a vent will make the oven more prone to smoking. Sometimes a higher vent can offset the smaller diameter but there is no fast rule of how tall is enough. A square flue is not as efficient as a round flue so not using a 10" round vent (recommended for a 42" oven) and the flue being square makes the efficiency even worse. Cross sectional are of a 10" ID round vent is 75.8 sq in. the clay flue is 45.6 sq in (and not as efficient as a 6" round vent). Smoking out the front of the ovens is caused by too small of a vent.

Squirrel or beaver tail is the configuration for having the vent stack at the center of the dome. There have been a couple builders using SS as well as clay flues (must be insulated).

Second, clay flue liners need to be insulated or the thermal shock from the inside to the outside will make the flue crack. David S posted a video showing this issue.

[buckeye_brian]

My vent opening is only 4 1/2" x 10" +/- now. Would it be better to set a 13" x 13" flue liner on top of this in lieu of the 8" x 8" flue liner? Should I build it out of firebrick and just not use the flue liners at all?

[david s]

https://community.fornobravo.com/for...238#post448238

[fhausback]

I originally was planning on the squirrel tail design, but had concerns about the dome supporting all that weight. After finishing the dome, i have zero concerns about that thing holding weight.

[buckeye_brian]

I started building up the base for the flue last night. My question is this: If an 8" x 8" flue liner is too small for a 42" oven; is a 13" x 13" flue liner too BIG? Is there such a thing as too big of a flue?

I mocked it up last night. My actual measurement of the vent is 5 3/4" x 11". Unfortunately I do not have the arch bricks back cut to be bigger at the bottom of the arch. I am hoping if I have issues down the road, I can cut them back from underneath with a 4" grinder and diamond blade.

I will take pictures tonight and post of what I have got going on.

[david s]

Flue liners are used in fireplaces to provide some protection of the bricks surrounding it from spalling. If you use a stainless flue pipe it makes the flue liner redundant. Your 5.75” X 11” vent results in an area of 63 sq” A 10” ss flue pipe is 78.5sq” A larger gather for the smoke before it enters the pipe works better, but a slight restriction there won’t matter too much. It will act like a Venturi with smoke accelerating at the slight restriction. The most important factor ifor decent draw s an adequate pipe diameter. A10” pipe will do the trick, skip the flue liner and maybe attack the vent area with the diamond blade, but see how it draws first.

[buckeye_brian]

Thank you for the advise! I have a lot to learn when it comes to this build. I got the flue base done and mocked up the final front entry arch. I need to get online and look to see where I can get a SS flue pipe.

I am assuming these are expensive. I am building a Neapolitan style oven. My ceiling is approx 16" high / 42" oven diameter. My oven is stand alone; probably 30' from my house, so nothing making me take the chimney up super high. Will a 4' section of pipe be tall enough to get a good draw?

[david s]

Yes, that should be plenty. The pipes I use for my ovens are 900mm long and I only use one, although with one crimped end extra sections can easily be added.

[buckeye_brian]

As you can see by the picture, I am still toying with the idea of using the 13" x 13" flue liner. Simply because I have it and I have 4-days of beautiful days (weekend as well) to work on this thing uninterrupted and I do not want to wait for a ss pipe to be shipped. My thought is to wrap the flue liner in 1" or 2" of ceramic insulation blanket and then lay brick around it for the actual chimney.

Will this remedy the chance of the flue liner cracking / breaking? These things have been used for 200-years. This is their purpose. Are they really something I should stay away from at all costs?

Anyway...I digress. I have 2-more days of laying base brick before I need to commit one way or another. I might just go to my mason supplier and buy 30-more fire brick and just lay it up with that and forgo the ss pipe and clay flue liner all together. They are on my way home from work. That would definitely work...correct?

See pictures of the progress on front entry arch. I brought out Vito & Tony to see how they will fit on the platforms on the left & right.

[david s]

Yes that will work well, although 2” of blanket is way overkill, 1” is plenty. The large volume of the big 13x13” flue liner will work well to gather the smoke. It may be sufficient on its own rather than having a pipe on top of it as well. It looks plenty high enough to me.