Blocking off old fireplace opening?

[CJRages]

First off, a big thanks to this forum for guiding me through the last year of wood burning decisions and activities.

My stove installation is nearing completion. A quick summary:
Purchaed home last year - found out the fireplace was a metal Majestic Zero Clearance (late 1970's) model.
Destroyed and removed entire Majestic fireplace and chimney system.
Installed 20 ft of Supervent class A ss chimney with a wall support, T, and thimble into the lower level of the split foyer house.
Chimney is housed in a sided chase running up the exterior of the house.
(This weekend) Installed the ceramic tile hearth over the concrete subfloor/foundation.
Have Jotul Oslo waiting to be installed.

My quesiton is: how would I seal off the fireplace opening while maintaining access to the cleanout located under the chimney support? My plan was to use a piece of concrete board cut to the size of the hole with a handle mounted on the board, but I know that this will not be a completely air-tight seal and thus I would probably lose heat behind the stove and up the chase.

I could really use some ideas here! Thank you.

 

[cmonSTART]

Hmm. Interesting situation you have.

How about two big masonry doors (metal studs, backer board, tile etc) which pivot and swing inward to open up. It sounds a bit complicated.

 

[BrotherBart]

How about a sheet metal block off plate just like we use for masonry chimneys with a hole in it for the clean-out to stick through. And leave the fireplace open.

 

[vvvv]

run a fat bead of silicone on the brix & under the perimeter of where the board's gonna land. allow to skin dry some then place & press board into place. masking tape on back of board so the silicone lands on the masking tape & wont stick to board. painters masking tape can be less sticky then regular masking tape. or u can cover the some dried silicone with masking tape, or???

 

[CJRages]

run a fat bead of silicone on the brix & under the perimeter of where the board's gonna land. allow to skin dry some then place & press board into place. masking tape on back of board so the silicone lands on the masking tape & wont stick to board. painters masking tape can be less sticky then regular masking tape. or u can cover the some dried silicone with masking tape, or???

Hmm... This might work. Wouldn't the silicone adhere to the masking tape and cause problems when I would try to remove the concrete board "door"? Or would the tape have to be replaced each time the door was removed?

 

[CJRages]

How about a sheet metal block off plate just like we use for masonry chimneys with a hole in it for the clean-out to stick through. And leave the fireplace open.

I like your thinking.

Would there be any beneift to putting some kind of heat shield/reflector piece of metal behind the stove in addition to the metal block off plate above?

 

[vvvv]

run a fat bead of silicone on the brix & under the perimeter of where the board's gonna land. allow to skin dry some then place & press board into place. masking tape on back of board so the silicone lands on the masking tape & wont stick to board. painters masking tape can be less sticky then regular masking tape. or u can cover the some dried silicone with masking tape, or???

Hmm... This might work. Wouldn't the silicone adhere to the masking tape and cause problems when I would try to remove the concrete board "door"? Or would the tape have to be replaced each time the door was removed?

tape is there only to keep silicone from adhering to the board. silicone has dried on skin when board is pressed on so to mold the bead to the board. after dry, silicone only sticks to the brix

 

[BrotherBart]

How about a sheet metal block off plate just like we use for masonry chimneys with a hole in it for the clean-out to stick through. And leave the fireplace open.

I like your thinking.

Would there be any beneift to putting some kind of heat shield/reflector piece of metal behind the stove in addition to the metal block off plate above?

If it is going to be all the way out front of the fireplace and later you think you are losing heat you could just add the rear heat shield to the Oslo.

 

[vvvv]

chimney pipe got 2" clearance to the wood? i cant tell from pic

 

[CJRages]

chimney pipe got 2" clearance to the wood? i cant tell from pic

Yes it does. The angle on that picture skews the perspective a bit.

I think I may attempt the silicone/tape/concrete board installation first. If that fails then, I'm back to the drawing board.

BB, after looking again at my setup I don't think that the sheet metal blockoff plate would work. The support has angled brackets and I used 2" channel iron to give me enough distance from the back of the concrete to mount the support. I would have to cut around all that stuff in addition to the clean-out in order to fit the block off plate.

 

[CJRages]

Hmm. Interesting situation you have.

How about two big masonry doors (metal studs, backer board, tile etc) which pivot and swing inward to open up. It sounds a bit complicated.

I have been considering your idea. It sounds really cool, but like you said a bit complicated. Would it work to have a single metal stud on each end resembling something like gateposts? I could mount hinges on each stud and attach to the concrete board. However, at this point I don't know how I would seal around the doors to restrict airflow through them.