Stone Veneer Finish & Weight?

I have completed the insulation layers, metal lath, and one coat of mortar (absolutely no stucco mix to be found in a 100 mile radius). As I prepare for the second coat of mortar, I am looking ahead to finishing my oven with a stone veneer. I have done veneer before, using larger stones, on a connected outdoor fireplace. I would like to finish my oven with a veneer of smaller stones, but a thread I read about the adding weight to the chimney has me questioning this. I see many ovens that have been finished with various stone/brick veneers, but I am wondering if there was a structural step added that would not add more weight to the arch itself. Shorter story: Can I apply a stone veneer directly to oven arch?
As always, thank you to Brickwood for coming up with such a great system and to the many posters here who are invaluable to folks like me!

Studying the great builds in the gallery, it’s pretty apparent that others have applied various veneers directly to the completed arch, without additional structural modifications. I guess I was just looking for a little reassurance.

Hi Bill,

Hope the pictures helped, but yes, you built a classic arched structure, which is going to hold up under a lot more than what you’ll be adding. You could probably also go up there and sit on the oven while it’s baking—it should be perfectly cool, but you’d probably not enjoy the smoke all that much! But it wouldn’t be bothered by your weight, the weight of the veneer, the weight of the insulation, and the weight of the stucco.

If I recall correctly, the thread that mentioned the chimney wasn’t so much about the weight of more bricks stressing the arch than it was about adding height to a chimney that by design simply lays on top of the oven. Even that isn’t more than a caution. It’s a stability issue rather than a weight issue.

So yes, be at ease about it, and I can’t wait to see how you finish!

Thanks, Matt! I appreciate the check-in for reassurance. I also kind of like the ide of sitting atop the oven while it bakes for me; it certainly qualifies as a throne of sorts and makes me the king of my pizza domain!

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Well, that certainly demands a photo-post here when you can! :slight_smile: Good luck!

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My oven is done, and both the curing process and first pizzas went great. Brickwood really does have this figured out!
I believe my final question (how to throw dough in the air notwithstanding) goes back to the chimney height. To match the chimney of my fireplace next to the oven, I would like to diverge from the Duratech chimney and cap; and I would like to add one course of fire brick and approximately 8" of clay flue to my chimney built to specs’.
This is the response in a thread that has me concerned about any additional chimney weight.

The Mattone Barile and Mattone Barile Grande models are based on firebrick and mortar on a 180 degree arch. We designed the arch and the entire weight of the oven to be centered evenly on the walls of the cinder block base so the added weight of an extended brick chimney CAN be held without reinforcing the slabs.

BUT - you don’t want any more than 3 layers of brick on the chimney (4 bricks per layer) unless you design a way to reinforce the chimney so the extra weight is supported by the hearth slab (cooking surface slab). You DO NOT want all that additional weight sitting on the oven’s firebrick arch as it was not designed to hold an extreme amount of weight. Adding additional rows of brick and mortar can quickly add hundreds of pounds being supported by the arch, and this can result in hairline cracking, mortar failure or oven failure (e.g. oven collapses under the additional weight. Keep in mind, each layer of brick on your chimney is about 30-35lbs of firebrick and mortar.

Well, congratulations on firings and your first pizza! Looks like you are on your way to working out the “up in the air” part. :slight_smile:

I now have a better understanding of what your question was up-thread. Doing a quick calculation in my head, I agree that another course would add ~35 pounds to the chimney. Let’s say your 8-inch clay flue adds another 15 pounds.

The difference between my example (admittedly graphic) of you sitting on top of the oven, and adding weight directly to the chimney stack, is that your weight is dispersed over a relatively large area of the arch and is carried in part directly to the hearth frame and slab by your legs and feet. The chimney is a “point load”—it is mass concentrated on one relatively small section of the arch, at its apex, and for good measure surrounding the void that you built in. The square shape mitigates that a bit by diffusing the load to either side…that’s why you either arch the bottom bricks or build that arch in with mortar (the lazy way, which I admit I took).

So…@BrickWood is certainly waving you off from building a tall brick chimney, and that’s for loading reasons. If I were him, I’d stick to my guns about that. If it was designed to support three courses, he can’t advise you that adding even one more course is okay.

He does say that he is talking about multiple rows—and adding just two additional rows adds a hundred pounds of mass once you include the flue. He also says that when you start getting into that, you have to find a way to displace some of that load so it is supported directly by the hearth slab.

Here’s a thought: I know you want to match the adjoining chimney. Would you be able to take any weight out of that final course by trimming them from the inside, like an “El”, turning them into a partial veneer, and setting the flue inside, resting on the third course? It’s a little off-the-wall, I know, but if each brick ends up weighing 2 pounds rather than 7, you’ve taken 20 pounds of mass out of the structure, just like that.

The drawback might be fragility, but you would still reinforce the brick with mortar between brick face and flue, which would tend to strengthen them, and they will be more like veneer that is not getting direct heat.

Just a thought, and I’d invite others here!

It took me a while to bring what was in my mind to how it might play out in practice. Now, add the theory, and I am glad to have revisited this while providing a bit more detail for you et al to work with. (By the way, I did cut arches into the first course of chimney bricks. :slightly_smiling_face:)
I can absolutely mill the bricks for the potential, additional course.
I can also go back to my existing top course and mill a ledge on which the clay flue would sit though, admittedly, this would take a bit more time and precision; but it may also result in negligible net addition in weight to the chimney structure. As I type, I am leaning toward this solution.
I really appreciate your careful consideration of, and detailed response to, my idea.
I feel better about moving ahead.

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