Angling Chimney Back over Oven Design Styles, Chimneys and Finish Discuss Angling Chimney Back over Oven in the Pizza Oven Design and Installation forums; James - Do you have photos of how you built your venting and flue on your oven? I understand that ...

[domenico]

James - Do you have photos of how you built your venting and flue on your oven? I understand that your flue is directly over the outside center of the dome. I’m building a 42” Pompeii and I’m running the flue above the center of the dome and looking for ideas on how to do this.

Any help I can get is appreciated.

Thanks,

Domenico

[james]

Hey Domenico,

I just looked back through my photos, and I only have one photo that isn't very helpful. Basically, I used a pair of off-set angles straight from the vent. I measured the length of the diagonal run between the off-sets to get close to center, and then framed the enclosure around the spot where the vertical pipe came up.

Hope that helps. Keep the questions coming.
James

[domenico]

Hi James,

The picture you sent me is extremely helpful. I was thinking of doing the same but wasn’t sure how to start…now I know.

Few more questions:
-did you use the 8”clay pipe?
-How steep were your angles?
-Did you rest your clay pipe on the dome top or did you have to build a support structure to suspend the weight off the dome?

You’re the Man.

Thank you,

Domenico

[james]

I've done it twice. One with Duravent, where I used two sets (4 total) of 30º angles and one with steel stove pipe wrapped with FB Blanket with one set of 45º angles (I wouldn't recommend the second method and I only did it as a test).

Using lightweight steel pipe means you don't have to worry about holding up the weight and you only have to strap and connect it to the enclosure frame.

James

[domenico]

James,

Okay, I’m reworking the venting design and taking your advice.

In the metal vent pipe did you use single wall or the double wall stuff? There is a huge price difference and because I don’t have any combustibles in the oven enclosure I’m leaning towards the single wall pipe. Do you think this will generate too much heat dispersion inside the enclosure?

I appreciate your feedback and again, thanks for helping me. I’m a novice at this so you help is very much appreciated.

Thanks,

Domenico

[james]

We recommend the Duravent double wall system. It is UL approved, it draws really well because it is so well insulated, and the outside stays cool making it easier to install. It has a 2 inch setback from combustibles requirement, which is nice. You can stucco directly on it and the exterior doesn't expand and contract and crack your enclosure. Also, it will last a very, very long time, so you don't have to worry about burning it out and messing up your enclosure. But, it's a little pricey.

If you go single wall, make sure you buy something rated well over 1000ºF for direct contact with solid fuel flame. B-vent will melt. You can wrap single wall with FB Blanket. Don't get single wall pipe anywhere near a combustible.

Good luck!
James

[dmun]

Single wall stove pipe is to connect woodstoves with chimneys. It's out in the open and easy to replace when it rots out every few years. If you're walling it in, you want something that will last forever.

[kebwi]

Reviving a very old thread...

...will terracotta clay flue liners "last forever", to borrow dmun's wording from the previous post? When using terracotta (that's what they're made out of, right?) what sort of dead space should be provided between the flue liner and any surrounding exterior (brick, chickenwire/stucco, etc.).

...on that note...would chickenwire/stucco separated from a clay liner by only a half inch or so (I'm speculating) get too hot for stucco to handle without falling apart?

[dmun]

...will terracotta clay flue liners "last forever",

Well, forever is a long time. That said, the ones in my 1910 house have conspicuously done better than the masonry that encloses them, and they probably are just fired clay, not the refractory material that the modern ones are made from. They are designed to be enclosed in masonry. The air space is a pretty modern refinement: as recently as the middle of the last century they were pretty much just bricked right in. I think the air space allows for differential expansion without cracking.

Just a note: We've had several instances of bare flue tiles cracking in heat, but in most cases the builders have just slathered on some refractory mortar and kept going.