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cvdukes 11-13-2007 08:56 PM

Ferro Cement Pizza Oven
Hi ya'll, I'm Craig and i've been lurking on the forum the past month or so. Wish I had read a few of the posts months ago before i commited a few things to concrete.

My oven complex is about three weeks out from completion...of course its been three weeks out for the past four, so something ain't right with the calender. Actually its just the little nagging details that take all the time.

I'm sort off the books here in my constuction. The oven complex is a monster retaining wall cut into the side of my pond's dam...risky, but I needed the space. there are actually 3 cooking ovens/ surfaces. On the left side is basically my oyster cooking oven... a fire box holding up a metal plate that will be covered with half cut 55 gallon drums. Still have to attach the hinges and now I'm thinking about coating the drums with a vermiculite concrete...more about that later. Base of the oyster pit is brickwork, but I have to admit that I'm no mason. "Function over form" best describes my methods.
Smoke from the oyster pit normally will be routed up a chminey made of 14 inch flue tiles covered with steel and concrete backer board. The flue tiles are oversized but were free for the hauling from a former coworker's husbands junkpile. Also, all the metal in this project (a lot!) came from another former co-worker in trade for a pickup load of turkey litter. All the concrete backer will be covered with fiberglass reinforced concrete (bonsal surwal)... looks enough like stucco plus adds strength.
I've also constucted a damper arangement that will allow the smoke to shunt into oven #2, the pig smoker oven. Pig oven is all brick with a couple of metal removable shelves. I figure it'll hold 200 pounds of porker. There is a firebox opening at the bottom of the pig oven that I can transfer hot coals from firebox 1 if I want to do hot smoking, otherwise, just shunting smoke will be for cold smoking. Also made some provisions to hang fish or jerky in the top of the pig oven when its in the cold smoking mode.
The pig smoker oven supports my pizza / bread oven. This is made from ferro cement, which is simply concrete mortar mix packed into an armature frame made of hogwire and chickenwire. Ferro cement is cheap but does take a lot of handwork. I know from reading this forum now that I didn't make the pizza oven the optimum shape and its probably too small.... consider it a cross between a dome and a barrel. Inside width is about 24 inches, depth is 28 and max height is 18 inches. It'll work, but one pizza at a time and the fire will have to stay at the back.

I ended up lining the inside of the dome with cone 6 earthware pottery clay because I didn't like the roughness of the ferrocement...(figuring the heat would fire it in place)...Big cracks developed in the clay as it air-dried becasue of how it adhered unevenly to the ferrocement. After a couple of sessions re-claying the cracks, I gave and coat the inside with the bonsal. Then, because I didn't want fiberglass particles flaking off into the food, I messed around and came up with a formulation of portland cement, fireclay and powdered kaolin clay (Just happened to have 1/2 bag of kaolin laying around from use with shrimp has ~35% alumina content so very heat resistive and retentive). Floor of the oven was made of a 2.25 inch thick smooth pour of the portland/fireclay/kaolin mix with a little bit of sand mixed in. The Floor is supported by a ferrocement slab (1/2 inch thick) resting on a couple inches of 5:1 vermiculite/portland mix.
Fired the pizza oven up two weeks ago for first time. Worry was that the mulitple layers would delaminate. Progressively hot fires in suceeding days. My infared thermeter maxes out at 968 degrees. Sunday I maxed it out in about two hours of fire. No delamination and just one minor crack. Temps were ~600 two hours after the fire died. 30 hours later, inside temp was still 95 degrees... thats without a door and with night temperateure dipping down to 36, so it seems like there is decent mass.
Building the outside enclosure now... more concrete board and lots of vemiculite. (Forgot to mention that I found a vermiculite mine about 90 minutes away that sold me 42 4-cubic foot bags at $5.60 each... more than the oven needs, but I got other uses for the rest when I put a new liner in the pool)....
Figure my cost for the pizza oven part of the project is less than $95. Haven't advanced to cooking yet as its a major construction zone out there, but I'll send some pictures when I get it cleaned up.

DrakeRemoray 11-13-2007 09:59 PM

Re: Ferro Cement Pizza Oven
We need pictures man!

I like the signature line...paradise is where you make it...that fits well with my philosophy.

pjk 11-14-2007 03:09 AM

Re: Ferro Cement Pizza Oven
Yep, I want photos too, it sounds great.

I'm only starting to learn myself from this site a little after I'd planned and purchased a heap of stuff, but sometimes you can't beat learning on the run. Like you, I figure it will all work somehow at the end of the day.

Well done.


cvdukes 11-14-2007 03:38 PM

Re: Ferro Cement Pizza Oven
1 Attachment(s)
Attached (i thinK) is a picture from last weekend. As I said, its a huge mess out there, but you might the gist of what I described. Most of my early construction photos are on my cell phone and I haven't figured out how to get those to computer.
I got a little work in this afternoon (80 degrees!) and was going to take a better picture but the wife took the real camera with her on a trip.
Still need to do some brickwork on the left end (oyster pit) and over the top of the pizza oven doorway. Been covering the roof of the pizza dome with tin (over lots of vermiculite). Plan to top it all off a 1 1/2 inch layer of vermiculite- concrete (vermicrete?)...figure it will dry to a rustic brown that kinda fits in with the rest of theme out there.

cvdukes 11-16-2007 05:56 PM

Re: Ferro Cement Pizza Oven
2 Attachment(s)
Figured out how to downlaod the pictures from the cell phone so attaching a couple of shots of the oven from earlier in construction.

First one shows the ferro cement dome from the back side (from the top of the dam). I figure the finished dome weighs about 250 pounds. It took three of us to get up on the base, and even then we ended up putting metal rails down from the top of the dam and sliding it down from above.

The second shot shows the basic ovens arrangements and the metal framing under the concrete backer board. The pizza oven vents out thru the smaller chimney in the center of the picture (shown only in its metal skin... since ahve covered with the backer board). Rest of the ovens vent thru the larger back chimney.
Weather here turned cold and windy today, so slowing down my construction. Mortared a few bricks in place, and they seemed firmly set so hoping the freeeze won't undo them.

pjk 11-19-2007 02:27 AM

Re: Ferro Cement Pizza Oven
Cool photos. I had to re read the original post to try and put it all together, but I think I've almost got it. Post a few more as you move along, and then when you light the little baby up for a cook.


cvdukes 12-10-2007 09:14 PM

Re: Ferro Cement Pizza Oven
4 Attachment(s)
Well, its been 4 weeks since I said that I was only 3 weeks out from finishing up. So a little update (and an explanation for the delay). And some pictures from yesterday.

If you recall , my project is a massive oven complex that includes a ferro cement pizza oven at the top and several other cooking chambers for full pig roasting and oyster roasts. The oyster roasting side contains a welded-metal framed stand built inside the brickwork. On top of the frame, there is about a 1/4 inch steel plate, covered over by a drum that will lift off... this is primarily for roasting oysters, but I can get a lot of other cooking in there if I want. When I did the brickwork, I mortared the metal stand in tightly...big mistake.
2 weeks ago I finished up the oyster side of the oven and decided to build a fire to make that the chimney serving everything other than the pizza would draw.

Good news is the big chimney works fine. Bad news is that I forgot to account for all the metal expanding as it got hot.

The longest dimension of metal in that side is about 45 inches.... at a 1000 degree temp rise, it expands 1/3 inch. Just enough to crack the bricks on both the front and back of the oyster cooker end.

As I mentioned before, I'm not much of a mason, so my brickwork isn't too pretty. Faced with cracking bricks and sloppy joints, I decided to cover the entire monster over with cement board followed by a healthy coating of fiberglass reinforced concrete as a stucco. So I added a few more weeks to the schedule. And the old elbow just doesn't do too well with smearing all the stucco... so having to take it slow. I should finish it all by the end of next week… at least that’s my new schedule.

Attached shows how it looks right now… halfway done with the stucco. And still have to come up with hinges for the doors. The doors are wood skins over a metal framework and I still have to add an insulating layer. Oh, and the roof is tin that will eventually be covered with vermiculite. It was in the plans to get done yesterday ‘cause we hit some abnormal high temps, but just didn’t work out. Maybe my schedule will be 2 more weeks!

From left to right in the first picture: Drum cooker (oyster cooker). Two doors under it are the fire box for it. Fire will normally be built in the upper firebox and large coals will fall through to the bottom where they can be removed (to go to the pig cooker side if needed). The pig cooker is the larger door on the right with its fire box underneath. Small wooden plug door in-between the two large chambers is a little warming box…just big enough to reheat French bread during oyster nights. The pizza oven is the chamber at the top under the peak rook. Its cantilevered backward into the wasted space of the slope of the dam. Everything under the pizza oven vents out through the big chimney at the rear (center of pic)…Pizza oven has the smaller chimney on the front. Extending on past the oven to the right is concrete countertop with planned wood storage underneath

Second pic shows the pizza oven with 1000 degree heat glow…notice I still have all my construction tools close at hand. And, Yes, I really run that mssy of a work site.
Third pic: Pizza anyone? Actually my second try at these little devils. First time, I couldn’t get the dough to release from the peel… toppings all had more momentum so they went flying into the oven before the dough. Pizza upside-down pie is not the way to go! These are better because I built them on parchment paper which slides fine. The paper turns brown in about ½ second and I had to move the pizzas off before the paper flared up…but the way to go for me.
Fourth pic: Two sourdough boules and some baguettes (supposedly pain de l”ancienne method…but haven’t mastered working with the really wet dough).

Enough for now.

Acoma 12-16-2007 10:20 PM

Re: Ferro Cement Pizza Oven
CV, I am quite impressed. Pizza and bread look great. Try corn meal sprinkled on the peel for nice release next time.

Xabia Jim 03-31-2008 10:23 PM

Re: Ferro Cement Pizza Oven
Okay Craig, ferrocement dome lined with a custom refractory mixture.

Can you provide thickness of dome vs delamination?
and what you'd do differently now?

cvdukes 04-01-2008 06:30 PM

Re: Ferro Cement Pizza Oven
1 Attachment(s)

Originally Posted by Xabia Jim (Post 28152)
Okay Craig, ferrocement dome lined with a custom refractory mixture.

Can you provide thickness of dome vs delamination?
and what you'd do differently now?

The ferrocement dome was about inch thick at the top but got thicker on the sides because the mortar was extreme bottom, maybe 2 inches thick. Was trying to get more a uniform inside shape then really worried about thickness, but even then the inside of the ferrocement was rough. Think I posted this pic already but you see what I mean about the roughness. Also if you notice, I didn't get the hogwire covered with chicken wire on the inside of the throat into the oven ..My mortar didn't even cover the wire.
The earthenware clay ended up being maybe 3/8 inch...with lots of alligator cracking that exposed the underlying concrete.
Inside layer of fiberglass cement probably 1/4 inch thick .
Kaolin/fireclay/sand mix maybe 1/4 -3/8 inch (if that).
Once the dome was in place, poured a couple bags of regular concrete on top of it thinking I need more mass...not a uniform thickness becasue as everyone probably knows, just cant pour concrete on a curved shape.

Things to do differently:
Make the thing bigger! I'm limited to 1 pizza at a time and not the optimal location for the maintenance fire.
Make the thing round!... I've got a weird oval oblong shape going...sort of a cross between the bread tunnels and a true pizza oven.
Probably did not need the earthenware clay...but it got it out of my garage. If anything is the weak spot that I worry about, its the clay... but since the inside was so rough it may adhere terrifically for life...other theory is that it protects the ferro-cement but I dont think it really does.
Spend more time to make the opening arch symetrical because the door plug made of vermiculite concrete doesn't quite seal as good as it should.
Insulate better under the hearth floor... underneath the pizza oven is another oven for smoking foods... When the pizza oven is full max temp, get readings of around 100-120 on the steel plate roof of the smoker.
Get hold of one of those steel domes that WILEY or MINE have and use as an inside mold for the ferro-cement instead of trying to handpack the mortar in by myself.

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