tile flue question

[cynon767]

If I want to use a clay tile chimney flue, do I need to use some form of masonry to support it, or can I use metal studs and backerboard to create a stucco chase?

[Les]

Re: tile flue question

I just sat mine into a bed of mortar then bricked around it. I did fill the gap between the flue and brick with the vermiculite/portland mix for insulation.

Les...

[cynon767]

Re: tile flue question

I should be more clear. When I say support, I mean the top end. The flue would be mortared to the vent transition I have built on my arch and the front of the dome.

I guess my question is this: Is a lighter weight chase, a stuccoed box basically, enough to support the top end of the chimney flue and the chimney cap? I don't want to have to build a massive brick chimney; I am not confident in adding all that much weight to the arch, so I would have to go outward of that and build quite a large brick enclosure. Plus, the head of the design committee says she doesn't want to create the "mausoleum" look.

[Les]

Re: tile flue question

Mausoleum's are cool. I think of mine as a crematory. I think you are good - gravity is on your side. The metal studs can carry a butt load of weight.

Les...

[jmhepworth]

Re: tile flue question

I used the steel studs to support the flue tile, with FB blanket between the studs and the tile. It's not moving.

This picture is the best I have. I put the brick on top of the steel, but the steel also surrounds the flue tile and supports it on all four sides.

Joe

[pwcoppard]

Re: tile flue question

I built a masonary flue, surrounded by metal studs and concrete board. The flue projected 1" above the top of the flue. i cut the concrete board close, then used a high temp caulk to fill the gap. I didn't use any insulation as i wanted to make sure i had a good draw. has stood up very well for more than 2 years.

[jmhepworth]

Re: tile flue question

Why would insulation affect the draw?

Joe

[pwcoppard]

Re: tile flue question

I thought, and I could be very wrong, that we wanted to keep the flue hot so that it would create a stronger draw. And the concrete board gets quite hot to the touch.

Maybe it doesn't matter, but i have fabulous draw, even with a large flue.

[jmhepworth]

Re: tile flue question

I had the same thought, but my rationale was different. By insulating the flue, it would loose less heat and stay hotter. Mine also draws well -- 5 feet of 8 inch flue tile (6 inch inside). I suspect it simply doesn't matter. The other reason I used for putting insulation between the flue tile and the steel framing was that I wanted to hold the tile snuggly in place, but I did't want to attach anything to it.

Joe

[cynon767]

Re: tile flue question

I have also heard that insulating the flue would increase draw by allowing the tile to heat up faster; but I've also read about leaving airspace around the tile to allow for expansion and movement. That's part of the question for me. Insulate, or airspace? How soild?

[mfiore]

Re: tile flue question

If you insulate with vermiculite/concrete mix, like Les, that should still allow for some expansion, yet provide stability. Many builders cover the entire dome with this stuff, and it works well. That's my plan. If you look at my pics, I used a steel framed surround with concrete board that I will stick on some stone veneer. The space in between is filled with vermicucrete. I think I went with the Mausoleum look that your wife was hoping to avoid!

[dmun]

Re: tile flue question

Insulate, or airspace?

The airspace IS insulation, as well as a provision for expansion. I think, in seismically active areas like California, that firestopping (which is a form of refractory insulation) is supposed to substitute for the airspace.

[cynon767]

Re: tile flue question

I live in Sacramento, which is a seismically stable area (knock on wood). But does the airspace alone provide sufficient insulation? Would it be better to put in insulation? If so, would loose perlite filling the chimney chase be a good idea?

Mike, that's basically what I'm thinking/hoping, but with a slightly smaller enclosure. Or possibly just a chminey tower with an igloo. I don't know... the conversation about design styles has reached a fever pitch around the house recently, as we're at a crucial turning point.