adjusting double wall 90s

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random thought, somewhat outside-the-box here: how involved is it to build a non-combustible wall? and how much does that reduce your clearances? Since i'm rebuilding both walls anyways, i could build that wall on the left with metal studs, then i intend to do Duroc with tile anyways. At that point i could shimmy the stove up to the left wall, maybe 5" off the wall or so? At that point i could remove the 12" horizontal run. it would just be the length of the thimble coming out of the chimney (which is horizontal i can't get rid of anyways) and then a 90 down and a 45 back. same basic stove pipe design as discussed above, but 12" less horizontal run. Would bring the total horizontal run down to about 16".
I thinks its unprotected walls, protected walls and not sure where concrete walls falls into...but you need to make it depending on what stove you will put in and maybe think future stoves. your stove manual will determine the clearances. How big is that stove room and is there a window, stairwell, or doorway to the outside? Otherwise your stove might need to be the small. Here is an example of the clearances for a jotul stove, but clearances can be different with many stoves and expensive heat shields on the stove. Maybe hook the stove up in the room to the chimney and see how it goes before building walls. In my opinion... 5 inches maybe with concrete walls and double wall pipe.
 

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random thought, somewhat outside-the-box here: how involved is it to build a non-combustible wall? and how much does that reduce your clearances? Since i'm rebuilding both walls anyways, i could build that wall on the left with metal studs, then i intend to do Duroc with tile anyways. At that point i could shimmy the stove up to the left wall, maybe 5" off the wall or so? At that point i could remove the 12" horizontal run. it would just be the length of the thimble coming out of the chimney (which is horizontal i can't get rid of anyways) and then a 90 down and a 45 back. same basic stove pipe design as discussed above, but 12" less horizontal run. Would bring the total horizontal run down to about 16".

This is for the Green Mountain 60 you have coming? Putting non-combustible coatings on top of 2x4 studs does not make the wall non-combustible, just remember that.

If it were a brick or concrete wall with no wood in, you would have a non-combustible wall.

You have a side clearance of 13" on that stove. I do not see anything in the document I am looking at about reduction in clearance with shielding on the wall. You could ask Hearthstone about that. If they allow a 66% clearance reduction you would be in business.
 
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This is for the Green Mountain 60 you have coming? Putting non-combustible coatings on top of 2x4 studs does not make the wall non-combustible, just remember that.

If it were a brick or concrete wall with no wood in, you would have a non-combustible wall.

You have a side clearance of 13" on that stove. I do not see anything in the document I am looking at about reduction in clearance with shielding on the wall. You could ask Hearthstone about that. If they allow a 66% clearance reduction you would be in business.
Yes, correct. I am building the whole wall from scratch, so what I am suggesting is Steel Studs. So it would be metal framing, with a layer of Duroc concrete board and then tile.
So not shielding, just a fully non-combustible wall. It'd be tile, cement board, steel studs, 2 or 3 inches of air space, and then the cement chimney. Nothing combustible.