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-   -   Vent transition for clay flue liner (http://www.fornobravo.com/forum/f9/vent-transition-clay-flue-liner-17012.html)

azatty 11-15-2011 09:59 AM

Vent transition for clay flue liner
 
5 Attachment(s)
I chose to use clay flue liner for my chimney, and I noticed a relative dearth of information about how to structure the vent transition to bear the load placed on it by the weight of the flue liner. There’s lots of stuff on stainless steel anchor plates, but I didn’t find much on clay liners. I’ve posted the attached pictures and narrative to give others ideas of how to do it.

I started with the proposition that I had to effectively transfer the perpendicular load of the chimney into the horizontal arch. Since my arch is pretty flat, I knew that a perpendicular load would collapse it. First, I buttressed the sides of the arch. I drilled into the slab, dropped in ½” rebar, butted cinder block against the arch, and filled the cores with concrete.

Second, I created a template from a firebrick split. It was easier to work out the shape with a split than a full brick, and they’re cheaper. I figured that the downward force of the chimney could be transferred horizontally into the arch if the vent transition pieces would essentially “pivot” into the arch as the load was place on them. So I came up with what I call the “scissors”—the brick that sort of looks like the Star Trek insignia (they reminded me of scissor trusses, so that’s where I got the label). I reasoned that scissors allowed the transition to essentially collapse inward under the weight of the chimney, and the legs would “catch” on the arch bricks and transfer the downward load horizontally.
On the end pieces (those that would be in contact with the inner and outer arches), I cut one of the scissor legs in half along the long side (which faced the interior of the vent) so that the end pieces would be in contact with the arches rather than “float” like the pieces in the center of the transition. The original plan was to place most of the weight on the end pieces, so I wanted a lot of contact with the arch.

Once I had the scissors cut, I figured that I needed some bracing across the open span for the “floating” pieces. I cut some “ledgers” (long horizontal pieces) to rest on the lip I had cut at the top of the scissors. Then I cut two fat “T” shaped pieces and placed then perpendicular to the ledger on top of the end pieces, and the whole thing was locked together.

In the final assembly, I modified the ledgers to be “L” shaped pieces and I shortened the “T” shaped pieces so that the top would be level. I built up a “sleeve” for the flue liner using half bricks, and cut a shelf into each of the four sleeves pieces for the flue liner to rest on.

Hopefully the pictures and narrative are sufficiently descriptive. Pardon the ugly masonry work; I’m a lawyer, not a mason.

azatty 11-15-2011 10:04 AM

Re: Vent transition for clay flue liner
 
4 Attachment(s)
More pictures.

azatty 11-15-2011 10:07 AM

Re: Vent transition for clay flue liner
 
1 Attachment(s)
Last picture showing buttressing.

david s 11-15-2011 11:17 AM

Re: Vent transition for clay flue liner
 
That is an excellent solution, I'm sure it will work extremely well.

C5dad 11-27-2011 04:06 PM

Re: Vent transition for clay flue liner
 
Atty,

Great job on the brick transition. I have torn my old one out and am playing with a temp until I could figure something out. I think you may have broke the code from my perspective. And here I was getting ready to cast a transition.

Gulf 11-27-2011 04:42 PM

Re: Vent transition for clay flue liner
 
I like that. I am planning a small fire place type look for my entry. I will have to study on your transition a little closer. Great job! Please keep us informed on how it performs.

PS, Just in case that I don't finish my oven by Christmas: Do you know any good lawyers in the southeast who specialize the BIG D:eek:

azatty 12-05-2011 08:38 PM

Re: Vent transition for clay flue liner
 
Quote:

Originally Posted by C5dad (Post 124054)
Atty,

Great job on the brick transition. I have torn my old one out and am playing with a temp until I could figure something out. I think you may have broke the code from my perspective. And here I was getting ready to cast a transition.

I'm just up the road if you need to see it in person. I'm just now starting the steel framing for the enclosure, so the front is still exposed. But you're a better engineer than I am, so you'll probably have a CAD of a superior design in a couple days anyway.

C5dad 12-10-2011 11:13 AM

Re: Vent transition for clay flue liner
 
CAD, me? I am laughing. I use pencilcad 2000 for my design work. I never had the time to learn and my job is just getting busier - with the price of copper so high, the company has us working on a lot of projects.

I am still working on how to deal with a corner install for the roof transition. My thoughts are to take the brick back over the dome to push the chimney to the center for easier framing.....

My hopes are that with 2 weeks off for the last part of the year that I could get the work done so I can start the framing design. Now to deal with 24 foot steel frame rails that are so prevalent for the heavy guages. Flatbed anyone?

Hope you all have a restful weekend.

Chris

eatingmorefood 03-25-2012 08:35 PM

Re: Vent transition for clay flue liner
 
You guys are truly quite detailed with these transitions. I used a recycled stainless steel "Food Pan" cut a hole and welded a 8 inch stove pipe flange to it, on top of that sits a 6 ft. stove pipe chimney (oven works great) : pictures here: DIY pizza, Pizza Making Supply, DIY Pizza oven, DIY pizza-ovens, DIY wood ovens, pizza Cutter, Pizza Stones, pizza knives, spice shakers, cheese shakers, crushed red pepper shaker, grill pizza, grill pizza, pizza Q, BBQ pizza, make pizza grill, makin Oven is built of mostly "FREE" recycled materials !

Gary Mots 03-26-2012 11:38 AM

Re: Vent transition for clay flue liner
 
Eating More, every time I go to that site, my computer freezes up and I have to do a cnt alt delete?:confused:


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