Custom brick oven - not getting hot enough

[Mfacchini]

Ciao everyone, hope you can help. I have a brick pizza oven we built from scratch in Chicago IL. We used refractory cement and fire brick on top for the floor, and then firebrick, refractory cement and insulation for the walls/dome. Then have Chicago common brick on the exterior/face of the oven for looks (to blend with outdoor kitchen). The dome walls sit on the firebrick floor.

I am finding that I am unable to get optimum temps unfortunately. I'm no expert, but I believe it's in part due to Chicago rain/snow creating moisture that soaks into the brick and inhibiting the oven from heating efficiently. I need to get a good cover or something I suspect, to try and minimize water intrusion. Brick is like a sponge as I'm sure you know, especially Chicago common brick. I am also going to try to find a way to seal the brick better with a masonry product - try to keep water out, which again I suspect is contributing to my cooler oven?

Next, I don't believe the floor was insulated properly by my mason. Too late now, so I'm wondering if it makes sense to invest in a refractory floor by Forno Bravo, or if there's another solution? I just can't seem to get the floor hot enough to cook the crusts well, and perhaps the oven temp overall suffers because heat is lost thru the floor? Not sure, I'm just throwing out theories here.

I've spent so much money & time on this thing, with nothing but frustrating and disappointing result. I really hope I can narrow down the issues & figure this out. At this point, with my limited knowledge, I suspect moisture and a less than ideal floor are 2 of my problems, but could also be that the chimney isn't in the right place. I've dreamt of having this for years and it's been a pretty big failure thus far, so any help would be appreciated!

[UtahBeehiver]

Is there any insulation under the floor bricks? As you may suspect, if the floor was not insulated, the hearth that the floor sits on acts a heat sink and draws away floor heat. There is not a lot that can be done unless the floor can be removed and insulation added. A live fire will help during the cooking process.

[NCMan]

While trying to say this as nicely as I can, I've seen many, many "ovens" built by masons that looked splendid, but just did not work correctly. While having done lots of masonry in my years, it in no way, shape or form means that a "mason" knows a thing about how to properly construct a properly functioning oven. Builders should just know this, while seeking someone to build an oven. Obviously, insulation or the lack thereof is the far and away main reason for failure, along w/major design flaws. It's critical to an ovens performance. Anyone considering a mason to build their oven, should ask him/her all about what kind of insulation and how much and where they plan to use it. If they don't have a ready and informed response, I'd look elsewhere. As has been discussed, there really is no proper way to fix a lack of insulation under an oven. Just because someone knows how to sling mud and brick around, does not mean they know a thing about oven building. Just cold, hard facts. Having said all this, if you can find a good mason that actually does know how to build an oven correctly, then you've found just what you want/need. That would be the person to hire, assuming you can afford them....

[Pizzarotic]

if you can find a good mason that actually does know how to build an oven correctly, then you've found just what you want/need

He already has the oven built and needs advice on fixing the issues with poor temps.

[Pizzarotic]

I suspect moisture and a less than ideal floor are 2 of my problems, but could also be that the chimney isn't in the right place.

Sounds like you already have it figured out.

1. Floor installation or lack of will be difficult to rectify.
You could try jacking the oven and slide a ceramic fibre board under the floor.

2. Try heating the oven for a week to drive the moisture out, then do a cook and report back on the oven performance. Use a temp gun to provide temperature information. Definitely seal your oven bricks or build a roof.

3. Supply photos, measurements, etc of oven & chimney so people can provide advice.

[NCMan]

He already has the oven built and needs advice on fixing the issues with poor temps.

I totally get that. Once an oven is built, it's pretty tough to correct the issues, especially under the floor. He's already been told that, though. I was giving advice to future builders.

[Mfacchini]

Thanks all, I absolutely realize this oven could have been done better. I searched and searched, thought I had someone that knew what he was doing. He had built several before. It wasn't cheap to build, so I'm now faced with either finding a solution or tearing it down. You can guess what I prefer.

The floor has a 6" based of refractory cement. I've got a nice gas torch in there , coming from the floor, and can run it or burn wood. I usually do both to get the heat up. I can feel under the floor by going to the log bin below, and don't feel much heat coming out. But perhaps it's escaping elsewhere. I also think I need to move the chimney forward more, and also perhaps use a different exterior that doesn't allow water to penetrate like this Chicago common brick. So, it can be a combo of things.

For the floor, it's 6" of refractory cement with 2.5" fire brick atop. Have a couple pics attached. As you'll see, lifting the fireplace is not really an option. I could perhaps insulate underneath the refractory cement slab, at the top of the wood bin there, but not sure that would do much. It would also only be about 60-70% of the oven base (with the circular corners being left "uncovered"). Or I can add something on top of the existing fire brick floor. Or I tear it down. Any guidance is appreciated!

[fox]

If I read this right you have a 6” refractory floor with fire brick straight on top and no insulation in between, if that is the case that is most definitely the problem.

In an oven with fire brick floor and 4” of insulation it will take a couple of hours to heat through the brick but without insulation you will also then have to heat the 6” thick high mass floor and that will take for ever (maybe 6-7 hours) and then the heat will just escape into the air … so basically you will never get peak performance

To explain more… if you had bricks and insulation, the fire would heat through the brick, hit the insulation and start to super heat the brick until they are saturated with heat and be around 450c ….. in your case the fire travels through the brick and into a huge heat sink of solid concrete, that it then has to heat up before the bricks can saturate.
so basically you need to get some insulation between the two masses.
If it is at all possible to remove the bricks and place 2” of ceramic fibre board on the concrete and then re place the bricks that might work but there could be issues with door size etc.
some picture would help us no end…..

[Mfacchini]

Sorry, had issues uploading from my phone. Posting 4 pictures here....

[Mfacchini]

Appreciate the intel Fox. Not what I want to hear, but I appreciate you helping me get to the bottom of it. Now the question is whether I can do anything about it or if I need to knock this down. Seems like it's sounding like I need to knock it down.....unless I can remove interior brick, cut some of the refractory cement floor, add ceramic insulation (how thick?), and then try to put it back together? Or is there something I can just layer on top of the existing floor?

[fox]

Oh no it looks even worse as the chimney exits directly from the dome, not a good design I am afraid to say!
I do feel for you as it does look nice and must of cost you a pretty penny.
You could just except it as it is and use it within its capabilities or re build a more efficient design.

[Mfacchini]

I am going to look at building more of a tunnel entrance, then bringing the chimney down more, but I still have the issue of the floor. Per above, 6" of refractory cement with firebrick atop. Without demoing the whole thing, I'm wondering if there's a way to add to the floor, or remove the firebrick and put thin steel or insulation atop of the refractory cement slab, then fire brick on top of that thin layer?

[fox]

It will depend on how the dome was constructed and if the floor bricks are fitted inside the dome or if the dome has been built on top of the floor bricks?
Hopefully the floor bricks have not been cemented down (never recommended) and are fitted inside the dome walls, in which case they can be lifted out.
Once one brick is out, the others should come out easily.
Metal is no good to you in any case, you need insulating material not conducting material.
Any amount of insulation below the bricks will help, even one inch of ceramic fibre board would help but you really want two inches of insulation.
The bricks could be replaced with half thickness bricks as a compromise.
So if you can remove the floor bricks, assuming they are full size bricks, you could place one inch of board on the concrete base and replace the floor with half thicness bricks and you door opening would remain the same size.
A lot of ifs and buts, but without more build info to go on, I am only guessing …

[UtahBeehiver]

Feel your pain, it is too bad that all that money spent and not working out as expected, As Fox said, steel or metal will not gain you anything. It has a very high K value (IE ability of a material to transfer heat). If by chance you are able to remove the floor and install insulation, the dome walls still sit on the refractory base and will still act as a heat sink. Installation of half height floor bricks (aka splits) is an option but just be aware that the splits will not hold heat as well as full thickness so recharging may be required more often. They are just trade offs of any of these solutions. FWI, the outside looks great and you installed a nice certified gas control unit.

[JRPizza]

Just a thought and probably a long shot - if your builder is reputable and had implied he built quality ovens you might see if they were willing to build you an oven more in line with the pompeii specs for free labor with you buying any materials that could not be salvaged from the existing oven. The builder could "learn" how to build an oven that functions as well as advertised and could avoid a bunch of ill will and possible poor reviews with the oven as is. You would still have to put out a bit of cost paying for the CF board and insulation but not having to do all the work might be worth it.