Chimney Framing

[carrieanddan]

I have decided that the DuraTec chimney is out of my price range and so I am going with 8x8 clay flue liners. My question is can I box these in with steel studs and Durock, or do I need to build a masonry chimney around the flue liners. My Chimney needs to be at least 4 feet tall, I may need to go 6 feet given the proximity to my garage, and that is a LOT of weight on my stand that I did not design for if I need to build a brick chimney.
My thought was to use steel studs and box it in to support the flue liners, and face it with Durock (or some thing similar) and fill the space between with insulation. Any thoughts, questions, criticisms?

Thanks,
DAN

[james]

One thing to think about is the structure that will carry the weight of the flue liner. I would recommend a vent with solid walls (brick?) that will transfer that weight down to the oven hearth. You don't want to go to the hassle for framing something with metal studs to carry the weight -- I don't think.

In terms of framing it in -- which is a great idea; I like hiding the mechanics of the chimney -- you should be fine with insulation, metal studs and Hardibacker. Try downloading the Casa installation guide. It has content on codes for masonry chimneys.

How much of a setback were you thinking between the chimney and the frame?

James

[carrieanddan]

James, Thanks for the reply.
I have a brick arch at the dome and a brick arch at the door, and a brick vent transition (stepped in from the sides), which the flue liners will set on.
My plan was to use the steel studs to provide lateral support and to "hide" the clay liner, not to hold the weight.

I was thinking to use either ceramic blanket wrapped around the flue, and then put the steel studs up next to the blanket, or I had thought to use K-Fac 19, Mineral Wool board or some thing of that nature between the studs with a 1/4" air gap around the flue liner.

I could not find the Casa Installation guide on the FB store site, could you sent me the link?

Thanks,
DAN

[dmun]

You should be fine with the weight of the flue tile on your entry arch. I have maybe fifteen feet of the stuff on top of my oven, and it's a pretty thin one.

As far as enclosing it, code says that you need a half inch airspace between the flue liner and the surround. I used ceramic blanket insulation where the flue liner was close to the edge, and I didn't have the full four inches of masonry, as in right in front of the entry. This works fine, the thin brick remains cool to the touch even when the oven is in full fire.

If you were trying to do the cement board installation and were adhering to building code, I'd build the enclosure four inches or more larger on each side than the flue tile, then slide in half inch plywood pieces around the flue temporarily, and fill the cavity with insulating concrete. This would be light, and I don't think code cares what sort of masonry you use around your flue tile. It would also be strong enough to support whatever sort of chimney cap or collar you were intending to use at the top.

[carrieanddan]

Dumn,
Do I understand you correctly that I need to have some sort of masonry chimney around the clay flue tile?

I was thinking to make the "surround" with metal studs, and cement board, like I am doing on the rest of the enclosure, so that I can face it with tile or facing brick.

If I need masonry anyway then I guess I would not go through the hassle of building the stud work and cement board, since I could attach facing material directly to the masonry.

Any further input would be greatly appreciated.

DAN

[Muaz]

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