Masonry chimey repairs.

[EricPriddle]

So I have an old chimney that goes through my roof in the middle of my house, its been repaired by previous owners.

It has 3 flues, the middle one is currently in use and has a stainless uninsulated liner which goes to my woodburner (sealed insert) on my main level. The other 2 flies are old.

I gently removed the falling apart chimney to roof level, the center flue I bricked around above roof line, the others will get plugged and covered (as I'm doing my roof currently).

Here's my question, and what I plan to do. I bricked around the flue above the roof line, for the remainder, I'd like to frame around the flue with heavy gauge steel stud, 18ga, for structure, insulate against the flue with roxul, then wrap my steel structure in concrete board followed by 3/4 fire rated plywood, the top will be concrete board only, the chimney will be wrapped in metal, as with the roof. Then it will be topped with a stainless or copper cap.

The chimney comes out of the roof about 4 feet, just wondering if I really need to brick it to the top since I still would build structure around to put my metal on regardless, and none of which is combustible

Thanks

 

[bholler]

The plywood is without quesyion combustible. If you dont want to do masonry switch over to insulated class a chimney you can then box it out how ever you like as long as you maintain the required clearance to combustibles which is usually 2 inch the same you need for an internal masonry chimney without an insulated liner

 

[EricPriddle]

So I tore it down below the roof, bricked back up around the flue using 8x16x4 cinder blocks to the top, I added structure to the trusses to secure my fur out framing, then I boxed around it up to the top, using 2x4s, at least 2" from the cinder blocks, attaching my structure to the roof is strong, I think if it was any bigger I would have done my framing down to the interior of the house and not attached to roof structure.

The top of the fur out is concrete board, and the wood fur out framing is only so I can have a decorative metal diamond metal system to be installed to dress up the look as the roof is being done currently in metal as well.

Thanks for the pointers, I also looked up some codes as well, seems previously the roof sheathing shouldn't have been touching the masonry as it passed through the roof.