Question… recently converted a walled firepit into a brick oven. It’s more rectangular in shape, and I’ve got two natural gas burners on each side for the heat. I can get to about 500F and that’s on 1.5 hours of warming up. If I burn wood, would it warm up quicker and hotter?
Hi Jeremy, and welcome to the BrickWood forum.
That’s a very nice looking build. But we’d need to know some nuts and bolts details to respond to your question.
The biggest question for me is, how is the structure insulated? Is there insulation under the hearth? What kind of refractory material is lining the oven? Is there insulation surrounding it?
It seems like a relatively shallow interior and a big opening from the photo. I’m wondering how hard those burners have to work to raise the temperature to 500 F.
Again, it looks like a beautiful conversion and I’m sure there are construction details in there that would make a difference. We just can’t see them in a photo.
Unfortunately no ceramic blanket insulation, only brick and refractory cement. Burners are indeed working overtime. I do use a removable door to get to the 500F. Temperature gauge used is portable and sitting on the oven base/floor. Thoughts?
I don’t think burning wood will help you that much. If you have a double layer of firebrick in the walls and the floor, that could help a bit with insulation. But in general you have a very open structure that’s will lose a good share of the heat that is being generated. It’s also got a chimney in the center of the oven; we were just discussing this on another thread.
I’d suggest you experiment with burning wood along with the gas, and see if that heats up your floor. That’s what you really need to do to get a good crust on your pizza. I’d also drop $15 on an infrared thermometer gun (look for an upper range of at least 1,000 F). You won’t be able to measure heat on the floor properly with the instrument you’re using, even though it is resting on the floor. And if you’re successful, you will melt that one!
A next step depends on what you have now. If there is no insulation in the floor, you might consider taking out your hearth, installing an insulative board, and laying the hearth over it. I hesitate recommending adding a second layer of firebrick inside—very difficult to get that right.
And I know there’s nothing you can do about the chimney placement, but an adjustable damper will work with the door you have to retain more heat.
Let us know how you choose to proceed, Jeremy! I really like when folks upcycle structures like this and I admire what you are doing.
I’ve got a make-shift damper on now so that should help with the chimney placing hopefully.
I’ve also got an oven door I bought for this, so hopefully that helps in the heat up process.
Would it help if I add refractive mortar to the inside of dome and front/side walls for additional insulation?
Also another possibility is to build a step up on the hearth, essentially another layer of firebrick, so that’d be 2+ inches more elevation and added insulation?
If you’re up for it, yes, a refractory mortar liner would help, though I’d look into insulating castable for that purpose. @BrickWood would know more about that than me, but the caution is that you need first to scrub clean any surfaces on which you plan to apply it, and I’d also use a bonding medium. If you go that route, plan on a thorough fire-curing cycle over a period of about a week or else it will crack and come down into your food.
And yes, you could leave the hearth in place and step up over it. If you do that, I’d recommend a layer of sand for leveling, then a layer of facing brick (cut your bricks lengthwise) laid in a herringbone pattern. To make that work, you’ll want to add a “lip” across the entrance so you have an enclosure for the sand and firebrick.
The instructions for the various ovens include how to set up and lay the hearth brick, and why you’d want to do them in a herringbone pattern rather than perpendicular. The reasons you’d want to lay them over sand and not mortar them in are: 1. If a brick ever heaves (which happens both to mortared and loose brick) it won’t catch the lip of your peel—not as big a deal with your design but still a consideration; 2. If a brick ever breaks you just lift it out and replace it.
It sounds like you’ve got this, Jeremy. Hope this helps!
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Hey Jeremy -
@bikerbudmatt is 100% correct on this. And while reading the communication between you both, the only thing I can add…
Building a wood fire in the firepit (for an hour or more) will heat-up the hearth firebrick. This will ensure your pizza is cooked on bottom. BUT - if there is no insulation under the hearth firebrick (which there probably isn’t since it was designed as a firepit - not for baking), then your heat loss will be greater than normal.
There is no ceiling… or if there is, it’s too high. You will need a white-hot oven ceiling to bake the pizza / bread from the top down.
Did you have any success after building / trying a wood fire yet?