Building my Oven with a mix of plans

[Bmwdiver]

I didn’t want to intrude on Brianventura's thread so I moved my build to this one:

First a little back ground:
Many years ago i lived in Sicily (just outside Catania in Ficarazzi, Aci Castello) When I was there i fell in love with the Italian style pizza and fresh bread (goes without saying). I even rented a place from a man that made a living building brick ovens for the local businesses. He gave me a few pointers and guidance but never all of it but what he did instill has stuck with me throughout the years. Now 12 years later I finally have the opportunity (and space) to build my own.

for over a year now I have been researching (mainly this site) and trying to piece together what i remember from Salvo and Juicy (yes juicy is a common Italian name for a girl, this was Salvo's wife), the plans and guidance from Forno Bravo and what I learned from the Masons at the mason supply house up the street.

That leads me to where I am at today. I was hoping to get the dome built today, but since it seems like the rain is off and on I figured I would consult forum for input and guidance since it seems I may be headed down a bad road that others have gone before.

I will directly quote a few concerns that LBUROU and DMUN made that have me somewhat concerned. I think I may have the addressed but better safe than sorry and now is the opportune time to incorporate a change should there be a need. So if you have tried something similar and think I should change please let me know, Thanks

First of all Thanks you to Brian(Ventura) he provided the post that initially got me actively participating in the forum.

Originally Posted by Lburou

Great looking floor Brian (Bmwdiver)

You may have some difficulty down the road with a tall soldier course as pictured. The outward force of the dome tends to push the top of the soldier bricks outward and cause cracks, even dome failure....Unless you install a strap of some kind around the soldiers[/COLOR][/COLOR]. I went with a half brick soldier course. Also, the bricks are a bit more stable if the thin side is placed toward the center of the oven.
This is a good time to follow the proven design in the pompeii plans (forgive me for the negativity here, just trying to save you some grief ). Trust me, unless the guys down where they sell firebricks have made one of these ovens, they will likely give poor advice on building this race horse of an oven.
This forum contains report after report about 'expert' masons who either build or otherwise contribute to a failed oven. If you want the reliability and performance of the pompeii oven, follow the plans as closely as you can.

Originally Posted by dmun

Splits for the floor? That's not nearly thick enough. Is that vermiculite concrete underneath it? That's good if it is, but that means the entire weight of the oven is supported by that half inch concrete board. I've personally proved that a 2 1/2 inch brick dome is not a good idea.

We're all in favor of creativity, but not at the expense of structural stability. I'd second Lee's suggestion to re-read the plans and consider carefully before discarding their proven guidance.

1. One thing I remember Salvo stating over and over again was that "for the oven to live up to the fullest potential you had to maximize the brick face area inside the oven and eliminate any exposed mortar."
This is why i chose the broad face of the brick facing in. i did plan on installing a band of wire mesh around the soldier course after I had the set and the brick wedges installed. Then adding a supporting structure of regular brick outside the insulating layer up as high as the soldier course

A. I guess I should explain my wedges: Salvo built his oven's using no mortar between the fire bricks using and inflatable balloon and wedges cut from the same fire brick that were held in place with the insulating layer. This is what I had planned to do, even for the first course. Basically set up the first course (soldier) adjust until all the angles were the same, cut wedges to fit, install the band and secure to the front opening bricks. Then follow suit with the remaining courses. I watched him do it several time and he always made sure that the face inside the oven was always the larges surface the just added wedges under the brick between each course and pushed them in until the angle was set then locked the course in with a keystone.

2. Bad advice from "Expert Masons" I agree and was reluctant, but instead of asking how they build their ovens, I gathered information on mixes of insulating concrete and what each ingredient brought to the table: Basically i only relied on their collective knowledge of the concrete itself and not their building skills

A. Portland/vermiculite (Perlite)/lime/sand

Portland cement = bonding agent
Vermiculite (Perlite) = insulation/fire proofing
Lime = strength
Sand = adhesion
(At least i hope i got it right)

Most of the recipes i found balance the insulation and strength. One thing i learned was if you adjust to maximize one particular zone then the others and reduced (drastically). Needless to say i wanted to maximize the insulation properties and to compensate for the reduced strength and adhesion I planned to not rely on the hearth to provide structure to support weight or rely on the hearth to adhere to itself (basically hold itself together). that is why I added the center support wall in the middle (picture) and added stele straps under the cement board (not shown), then plan on adding a traditional brick and mortar structure to the surrounding area above the blocks and carry them into the hearth to completely encase the hearth so that it does not fall apart. (i tried it on a small test piece with excellent results). This allowed me to maximize the insulation attribute of the hearth to allow me to utilize the split brick for the floor.

My idea (Dream) is to
1. Completely assemble the dome with fire brick wedges and no mortar, then add the fire clay mortar to the outside.
2. Add insulating layer
3. build traditional structure from the block stand up to the top of the soldier course (providing strength) the attach wire mesh and stucco to the exposed top dome.
4. Stucco and brick the facade of the stand


NOTE: sometimes I let my engineering brain override common sense just to see if it works. I do not recommend this to anyone since 1) I have no previous experience 2) this has not proven to work yet and 3) following the plans is proven to work time and time again

[Lburou]

You deserve praise for being open to suggestions, and a willingness to reconsider your plans, it shows a mature personality

I didn't even imagine that the hearth pictured under your oven floor (in brianventura's thread) was what we call vermicrete or perlcrete Kudos to dmun for realizing that before it was too late for you!

The concrete recipe you followed is a formula for insulating concrete. It is NOT a structural concrete. It is weak as water when you consider the 1500+ pounds of oven you want to place on it (your excellent stand design notwithstanding).

My advice to one gathering information and making plans for building a pompeii oven is here. (A newbie’s survey of the Forno Bravo treasures hiding in the archives) You will see several resources linked there to read and get a handle on the basic components and process of oven construction.

Right now, I'm sure you need to hold off on your dome until you get a sturdy hearth in place. How you get from where you are now to that place is a matter for reflection and discussion.

New thread= Smart move
Redesigning your hearth= Smart move

Don't feel bad, we all have regrets. Fortunately, dmun came to your rescue in time to avoid a BIG one this time.

[Bmwdiver]

I had a break in the rain so I decided to lay out the band and outer brick to show "very roughly" my plan for when the rain stops.

I have added the outer brick structure to the height it will be then also added in the banding that will be tighty wrapped around the solider course after the wedges are in. afte the dome is finished and a layer of fire clay mortar is applied i will add the insulatng layer then fill the void between the oven and outer wall with a perite mixture that is more geared towrds structural. I think this will be enough to thake the load applied by the dome so that the oven does not collapse in on itself.

Any thoughts



Brian

[Bmwdiver]

The hearth was not the structura element. I added 1/4 inch steele bars under the 1/2 cement board spaced every 4 inches and recessed into the block to hold up the oven. The hearth was purely meant to be the insulating element. the concrete board extends out past the hearth and the encasing concrete will provide the side structue.

I was cncerned about the hearth and the elements (rain) until i get the rest of the structural components in place thats why it is covered in plastic.


Thanks for the advice. Icontinue to post progress reports and pictures.

[david s]

Originally Posted by Bmwdiver

The hearth was not the structura element. I added 1/4 inch steele bars under the 1/2 cement board spaced every 4 inches and recessed into the bloc
.

Steel and heat is a great recipe for rust, particularly if the steel is surrounded by air (oxygen) It is the major reason for failure of kilns unless the steel can be replaced easily or use stainless steel. it is doubtful if you could replace your under floor steel bars once you've built over them.

[david s]

1/4" sounds way too thin IMO.

[Bmwdiver]

All this talk about Structural load made me wonder if maybe I forgot a load path.
Ill briefly explain the major paths and how I was planning on dealing with them

Vertical load: Weight and Gravity

Cinder Blocks, 1/4" Steele bars, 1/2" cement board, 3.5" perlite insulating mix

Horizontal load: weight of oven pushing down on the hearth and the hearth wanting to push itself out

Conventional brick and mortar, 3" 6000 PSI concrete

Axial load (on soldier course): weight of dome pushing out on the top portion of the Soldier row

Traditional brick and mortar, 1.5" 6000 psi concrete, 2" insulating perlite concrete mix, 3/16 Steele wire cage surrounding first course, 1/4" fire clay mortar,

These are the main load I was considering, there are transverse and other loads within the dome but they didn't transmit much down and into the hearth.


Am I forgetting any major ones to consider.

[Bmwdiver]

Thanks David, I coated the Steele bars to prevent the rust.

I would agree that 1/4" is pretty thin and I would not have used it if the nominal span was 12" or so. But since the span where the load will be the greatest is a max of 5" I considered the risk low.
The largest span I have is the opening for the storage and it is dead center and only 16".

[dmun]

I'm confused here. Your soldier course is going to be held up with a length of coat-hanger gage steel wire? What's the wire supported by? Is it anchored to anything?
And your quarter inch pieces holding up the whole oven? How are they moored into the base? When you're considering the forces of your oven, you should consider two things: Steel has a considerably greater coefficient of expansion than masonry in heat, and similarly, an oven subject to heat-up and cool-down cycles is an object in motion. It's not a static pile of masonry.

[Bmwdiver]

Originally Posted by dmun

I'm confused here. Your soldier course is going to be held up with a length of coat-hanger gage steel wire? What's the wire supported by? Is it anchored to anything?
And your quarter inch pieces holding up the whole oven? How are they moored into the base? When you're considering the forces of your oven, you should consider two things: Steel has a considerably greater coefficient of expansion than masonry in heat, and similarly, an oven subject to heat-up and cool-down cycles is an object in motion. It's not a static pile of masonry.

The soldier course is held up by the shims and mortar applied to the back of the bricks, which will be done after the dome is complete. The Steele wire is to keep the course from tipping outward while the dome is being constructed, it is wrapped around the entrance bricks which are recessed into the floor. The wire will then be moved to the outside of the clay mortar and inside the insulating layer to provide additional support.

The 1/4" Steele bars are recessed into the block stand and captured on each end so that it can move freely but not come out. A 1/4" concrete board is on top of the bars and block stand. The perlite is on top of that.