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Origen: 36" Pompeii Oven Build: Just getting started and have some questions....

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  • gastagg
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    Origen, 5" may be enough. It depends on how you decide to finish off the oven. I used stucco and had about 2" past the insulation, which was enough room. If you're going to build an enclosure, then you may want to make the oven a bit smaller. I"m not sure about extending the slab. I've got a 33" oven. What kind of use are you planning on?

    Medium duty bricks are just fine for the dome.

    Don't mortar the floor bricks down. The floor insulation just sits on the slab as well. It's not going anywhere. Put some plastic down between slab and insulation, and raise it off the slab a bit. I didn't, but that's the best practice at this point. I think Randy's build explains more detail on that.

    Tapering the bricks is not necessary and creates a lot more work. Angle (cut from top view) and bevel (cut from front view) is what most builders do. I've attached a dome calculator, which is very helpful on getting started...only cut a few bricks at a time when you start the dome. Use a segmented blade for brick cuts. You'll wear the continuous rimmed blades down quickly. Keep the smooth part of the bricks toward the dome interior. Mortar will be the only thing on the other brick sides.

    3" of dome insulation is enough. Floor insulation is key. 2" is minimum. If I can remember someone's tech analysis of insulation thickness using CalSil, I think that 1" more improved performance by 14 degrees.
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  • Origen: 36" Pompeii Oven Build: Just getting started and have some questions....

    I'm getting ready to start a 36" Pompeii style build. I have attached a few photos. As I was laying out the templates, I'm thinking my hearth might be a little narrow (that slab is 57"x67"). I know the Forno plans showed larger, but when I was scrambling to finish this in November, I got tired of handmixing concrete! On the width, I only have 5" after the floor and the first course (see photo); I'm planning on using 3" of blanket, so that leaves 2"! I was originally thinking that I was going to bolt angle iron to the sides so that I could brick around the dome--either with another dome, or vertical walls and put a gable roof upon the walls. I could also dowel into the existing slab and pour extensions; I suppose I could do that after the dome is built. The vent opening is 19"; the vent landing is approximately 14" long. The floor is 36" diameter; I'm planning a dome height of 18 or 19". So my first question is--what do you think? Is that slab size OK? Does the layout look OK?

    Other questions that are I have: I'm planning on using 2" SuperIsol below the oven floor--do you mortar down the SuperIsol, or let it float? Do you use refractory mortar or fireclay as with the oven floor bricks? Just curious: would it be acceptable to let the floor bricks float, as opposed to fireclayed down? And speaking of 2" SuperIsol: is that enough? I reviewed the RandyJ build very closely, and I really liked the performance of his oven. I think he used 4" below the floor. I think he used 3" blanket, but also filled the house with vermiculite. So, does that killer oven performance come from the entire insulation package, or the insulation around the dome? I know a little about the diminishing returns of added insulation in areas other than a WFO, but, I would like some advice in this area.

    Are medium duty firebricks OK? The bricks I have for the floor are medium duty and meet the specs outlined in FornoBravo's instructions. Is it a better dome with heavy duty bricks? I can easily get heavy duty bricks for the dome; the supplier even suggests that they are better for WFO's. What do you think?

    I like the idea of cutting the "tops" of the first course bricks on an angle. I assume that the angle is the same as the angle on subsequent courses--is that correct? Will that angle be determined by the I.T. or does it need to be calculated? I do want to taper cut the bricks for the dome courses, and I'm not quite sure how to do that; I'm going to look at some data and see if I can figure that out.

    Regarding cutting bricks: what type of blade? When I cut masonry or concrete, I usually use a segmented blade, but it seems to me these bricks maybe should be cut with a continuous turbo edge blade. I cut a few with a segmented blade and it seemed a little aggressive. I cut a few with a continuous rim diamond blade (not a turbo edge) and the cut was smooth, but slow and a little gentle--tentative.

    Would it be best to keep the posts shorter than this? Seriously...
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