A try at a stacked fireplace-pizza oven

[scalpel]

I attached a drawing of an outdoor stacked fireplace-pizza oven design. I put this together after going through all the great information on this and others and learning as much as i could regarding the design considerations when putting one of these things together. The following are my goals for this project:

1) A 100 cm brick oven that makes great pizza for family and parties
2) A fireplace that we can use for ambience (less for heating)
3) Use of the oven as a smoker or roaster when a fire is lit in the fireplace

I had seen on the site a number of discussions regarding the stacking of a pizza oven on top of a fireplace where they share the same exhaust chimney though I haven't seen anyone that has finished a project like this.

Some important points about the design:
1) The top of the fireplace is a stainless steel hood that will also act as a permanent form for the vermicrete pour. I am relying on the vermicrete to insulate the concrete slab above from reaching temperatures that may compromise it's integrity
2) The exhaust from the fireplace will enter the vent landing area bordering on the lip of the dome
3) I intend to install cast iron door that can be opened towards the dome in the opening of the exhaust as part of a heat brake
4) I will have an internal and external door for the openings of the oven to better control the smoke from the fireplace. With both installed I would assume the vent landing will act as a regular smoke chamber of a standard fireplace.

I broke ground a couple of weeks ago and poured an elevated base (a couple of inches above the ground due to the proximity to a large tree), I am now about to purchase the rest of the materials needed to complete the project.

Before I actually starting laying block and brick I would really like to hear any inputs that you guys have from your builds or ideas about the design that would be relevant. I labeled the drawing to try to clarify the components in the design.

Any inputs will be greatly appreciated and thanks for all the info that you guys put on this site. I could never have even considered this project without the wealth of info that you have made available!
Eric

[Gulf]

I had seen on the site a number of discussions regarding the stacking of a pizza oven on top of a fireplace where they share the same exhaust chimney though I haven't seen anyone that has finished a project like this.

I've seen several talk about it and presumably went on to build a combo. Though, there is not very much feed back on how well they work. One, who had a contractor install a combo, had the concrete support slab to spall. I believe he said that it "exploded" under his oven. My best guess to why there is so litlle feed back is that they just don't really work out like they were expected to. Fireplaces and WFOs draw and work well when they are built to certain specifications. Marrying the two in one unit is above my pay grade.

I have a WFO and I also have an outdoor fireplace. They are a little distance apart. I personally like it that way. I can fire them both at the same time. It is also nice to have the fire gawkers intertained and out of my way while I'm working the oven. Actually, I have the fireplace set up for certain types of cooking as well. There is always someone there who will be glad to stir the collards, beans, or the turnip green soup .

My advice is to build them separately.

[scalpel]

Thanks for the feedback Joe.
I read a previous post on the concrete slab that heated up and spalled on here and that was the trigger to add all that insulation between the hood and the slab.

No doubt that a side by side would be the safer proposition, I just don't have the space

I also didn't think about the fact that it might be a problem cooking in the WFO with the fireplace lit, besides blocking the view for the fire gawkers it might get hot in the lower torso... I'm gonna have to get myself a pair of fire resistant underwear!

and I'm definitely the guy that stirs the soup! Sometimes it's nasty, sometimes delicious but it's always exciting

Eric

[Gulf]

Eric,

I can't tell from the plans on openings and flue sizes. Just saying that both doors to the oven are closed, the fireplace is lit and the entry is performing as sort of a smoke chamber. The flue for the oven is now the flue for the fireplace alone. The fireplace has a much larger opening than the oven. Have you researched what size flue you would need for your fireplace? We usually figure the cross section area of the chimney/flue to about 1/10th the area of the opening of the fireplace.

[scalpel]

Sorry for the late response, was out camping with no communication.

So my flue size is about 1/7th of the fireplace opening, I assumed that bigger is better but is there a limit that I should watch out for?

Eric

[Gulf]

For a fireplace, you would want to stay fairly close to the 1/10th of the fireplace opening to flue ratio. I know that they say on here that "you can't over flue an oven". Maybe not practically, but you can. You can definately over flue a fireplace. A 100 cm (39") oven is recommended to have a usable flue cross section of about 322 square centimeters (about 50 square inches). I hope that my conversions are correct.

What are the diminsions of your fire place opening, flue diminsions, and from what material will your flue be constructed?

[texman]

I am with Gulf. Seperate them or pick one of the two. I would pick the WFO. You will get plenty of radiant heat from the WFO and flame ambiance if you choose. Gonna be really hard to negotiate the oven with 1000 deg gases coming through burning your handle and dumping ash in your pizza. I just dont see the point.

[scalpel]

It's been a while, it's not easy negotiating the time between updating the thread and working on the oven

So I've taken some of the feedback and modified my design. I now have two exhaust ports entering the oven on either side instead of one in the middle.

A few points regarding the build:

1) I elevated the base to prevent root damage since the only place I had to put it was next to a tree

2) I used decorative silicate blocks to construct the walls of the structure to save the need for added masonry for the finish

3) The floor of the fireplace is from firebrick, the walls are a vermiculate, nhl, portland and sand mix. I tested the mix in an oven at work and cycled it at 500C, held together well so I decided to go forward with it.

4) I used a 60 cm hood that I had laying around as a form and poured a calcium-aluminate, vermiculate mix x 2 and used that as the top of the fireplace. Each exhaust port will go to opposite sides of the oven.

5) Got a good deal on a cast oven that turned out to be much cheaper than buying the firebricks that I needed for the build of the oven but I'm making my own floor rather than using the one provided


pics are on their way

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The columns and the platform for the elevated slab

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Forming of the top of the fireplace using a hood that I had lying around

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Testing of different mixes for the walls, in the end I used 1 part portland, 1 part NHL, 1 part sand and 4 parts vermiculate

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Current pics of the project