Help - Pizza Oven Fireplace design

[david s]

A few years ago a member built a similar set up, but unfortunately it was a major failure because the supporting slab for the oven was cast in normal concrete and the heat from the fireplace destroyed it. Not only is standard concrete susceptible to heat, but the use of heavy rebar in conjunction with it leads to expansion issues when heat is applied suddenly. What material and reinforcing are you planning to use for your supporting slab and how high from the fireplace hearth are you planning it’s location?

[david s]

Here are some pics of an oven in Panzano that uses the oven in the fireplace design. There are many in Europe that use this idea, particularly in castles. The design has the advantage of using the fireplace chimney therefore not requiring a flue gallery. Most of these ovens were also not insulated over the top as the fire from the fireplace kept the dome hot externally.

For some reason I can't attach pics, I'll try later.

[MarkJerling]

These are the combos I have seen.

Thanks for posting the images. Evidently, it is possible. They must have some flue gather at the top which allows them to flue the fireplace past the oven. I doubt it would be out of the back wall as you have sketched. It's more likely that they go to the top rear corners. But, with luck, you can find some information on how they did it. It seems their fireplaces are quite deep, where as your design sketch has the fireplace somewhat more shallow.

[MarkJerling]

I just found a thread with information about a combo oven: Inside Firplace/ outdoor Pizza Oven Combo (One Chimney) - Forno Bravo Forum: The Wood-Fired Oven Community

[nhans]

Hello Dave ...... the slab would be 5000 psi concrete with #4-5 rebar. Beneath the slab, my thought is to place firebrick and possibly a layer of vermiculite between brick and slab. Like a sandwich ....... 1st the bottom form. 2nd the standard thickness firebrick with refractory cement laid from above. Maybe 3rd 1 inch vermiculite and Lastly ..... concrete reinforced slab on top. Leave bottom form for 2-4 weeks, then remove.

Theoretically the fire brick/ vermiculite / concrete will all adhere/ cure together and provide sufficient insulation from fireplace.

If the hearth/ floor and walls don’t crack or explode due to firebrick insulation/ protection, why wouldn’t the roof/ ceiling be insulated?

The questions I have are
1. Will vermiculite adhere to concrete
2. Will refractory cement/ brick adhere to vermiculite
3. Will this be enough heat buffer/ insulation to protect the slab? Also I could do 2 layers of refractory brick.



The ceiling firebrick will be approximately 26” from hearth

[nhans]

Hello Mark

Is a fireplace able to be vented out the back? Does it have to go straight up? I was trying to compare a wood burning fireplace that has the flue out the back of stove, vents outside and then goes up chimeny/ flue.

It may not be pretty but functional.

[david s]

Flue’s should never run horizontally. Never go flatter than 45 degrees or expect smoke issues.

[MarkJerling]

Hello Mark

Is a fireplace able to be vented out the back? Does it have to go straight up? I was trying to compare a wood burning fireplace that has the flue out the back of stove, vents outside and then goes up chimeny/ flue.

It may not be pretty but functional.

As David has said, never run flues horizontal. Not for wood fires anyway. With your sketched design, almost all the smoke will come out the front and not up the flue. A possible solution would be to have two smaller chimneys left and right of your oven mouth so that the fireplace below vents up into those two chimneys. In practice, what you'll find is that one of the two will draw better than the other, so your flames will almost always go to the one side, but at least it will work. Alternatively, you'll need to slope the top of the fire and have the fire super deep so that you can flue up past the rear of the pizza oven. But, for a shallower fireplace design you'll have to chimney to the front corners making sure that you have a nicely sloped top surface in your fireplace directing the smoke up into those chimneys.

[MarkJerling]

Here is what I did with it..

That looks super impressive. What lives in the pull-out baskets?

[Gulf]

[QUOTE] .......What lives in the pull-out baskets?[/QUOTE

Just about everything imaginable for the oven and my wood/charcoal grills. Emergency battery powerd lights, Lighter wood splinters, lighters (some are survival type lighters) the list goes on. Underneath the drawers is room for pizza peels etc. I even keep a little moonshine whiskey.... for medicimal use only

[MarkJerling]

[QUOTE=Gulf;n433521]

.......What lives in the pull-out baskets?[/QUOTE

Just about everything imaginable for the oven and my wood/charcoal grills. Emergency battery powerd lights, Lighter wood splinters, lighters (some are survival type lighters) the list goes on. Underneath the drawers is room for pizza peels etc. I even keep a little moonshine whiskey.... for medicimal use only

Great stuff! Very innovative.

[NCMan]

There is a guy on Facebook in one of the groups that just finished such a build. He seems to like it. I can send his info if you like. If interested, send your email, etc. I don't want to post his name, etc. I had given serious thought to doing such a build, but changed my mind. Will instead be doing them joined, but side by side on my new upcoming build.

[Gulf]

NCMan
Great Choice! A side by side eliminates the main problem in designig a combo. The smoke chamber. There is no room to incorporate a proper one in to the fireplace of a stacked design. A smoke chamber is a must for proper draw in any fireplace design. Imo a Rumford style fireplace works better for an outside fireplace.( I'm not talking about the Buckley Rumford Company. I'm talking about the original design by Count Rumford) . They throw more radiant heat to the front as well as to the sides which is what I want to keep folks from crowding the fireplace opening on cooler days. A Rumford fireplace style opening is taller than a typical fireplace.(that alone would make it dificult to install in a stacked design) It is also shallower and the sidewalls have more of an angle. That is what makes them better. Radiant heat is all that you get from an outside fireplace. You can't heat the neighborhood or even the backyard no matter how hard you try. Mine is separated from the oven by some distance. It is a simplified version of the original design. It has no damper. no smoke shelf, and the chimney/flue sets directly on top of where the fire is built. The draw that is created is all that I could ever hope for. For a side by side with a Rumford style fireplace, it would be great to have a very small fire in one while cooking on the colder days to keep warm. But, I would wait until the cooking is done to ramp the fire up .

[david s]

The oven in the fireplace rather than under it is a better solution IMO. This villa was over 400 years old and presumably the oven was pretty old too. I"ve also seen much larger ones in castles that use the same idea.

[Gulf]

I could definitely live with that design! Brings both oven and hearth cooking together.