Block off plate with uneven brick

[farger04]

Does anybody happen to have any ideas on how I should go about making a block off plate for this set up? As you can see, the installer had to chip away a lot of brick to get the liner in there. Where the brick is cut is very uneven. My current plan is to make a three piece plate, one for the middle with a hole for the liner to push back into the uneven slot and then two for the sides which will overlap the middle. I'm still worried about being able to fully seal it, even with a lot of caulk. I've cut up a bunch of cardboard and the best i can get still has some pretty good gaps. Anyone have any other secrets or ideas? You all seemed to have such clean finished jobs, i can't imagine i'm the only one with such uneven brick.

 

[weatherguy]

Mines a little uneven too, I made a template with cardboard then traced it onto a piece of sheet metal.

 

[maddog1016]

Looks like you might be better off just cutting a square or rectangle and having it overlap the uneven brick. Paint it black with high temp spray paint if you want it to blend in a bit.

Otherwise you could try using a ticking stick to get a pretty close template on cardboard.

 

[farger04]

I don't really care how it looks since I have a surround which will cover everything. My main concern is getting a nice airtight seal. The ticking stick is a good thought, I have one so I might give that a try to get closer. I have a tube of the red high temp rtv silicone, is it ok to just glob that all around the perimeter of the plate? I would also apply it where the plates overlap and then secure them with SS sheet metal screws.

 

[maddog1016]

I don't really care how it looks since I have a surround which will cover everything. My main concern is getting a nice airtight seal. The ticking stick is a good thought, I have one so I might give that a try to get closer. I have a tube of the red high temp rtv silicone, is it ok to just glob that all around the perimeter of the plate? I would also apply it where the plates overlap and then secure them with SS sheet metal screws.

Then I think overlapping over the brick will give you a better air seal. Clean the brick so the silicone gets good adhesion, apply the high temp silicone to the brick, press on the sheet metal, and attach the sheet metal to the brick with a few masonry screws. Make sure to pre-drill the holes in both the masonry and sheet metal (and make sure the holes line up with each other). Coated tapcon masonry screws have always worked well for me.

 

[farger04]

Sounds good. Thanks for the suggestions. I'll definitely have to get in there and scrub it down and vacuum. As can be seen, the fireplace used to have an old insert in there without a liner, so the brick is all sorts of dirty. When you say "overlap the brick", are you talking about just bending down a flap of the sheet metal to press against the brick? Or do you mean something else? It would be awesome if I could undercut the brick a bit to create a slot for the plate to slide into. Maybe I could make that work with an oscillating tool. It's a bit tough to work in there because I don't have the means to remove the insert, and it's pretty difficult to push the liner up much more, it's pretty snug in there.

 

[maddog1016]

I'm thinking cometely cover the uneven spot. In my photo below picture the red area as the block off plate. Bend the top of it into a 90° if you need to get it to cover the top of the opening as well. Like a big L shaped plate.

 

[farger04]

Ah. So I had thought about trying that but unfortunately the liner goes back into that slot too far (its hard to tell from the picture). And the soot covered masonry slopes forward towards the liner at the top further reducing the clearance. So I can't get a flat plate back there unless I actually bend it around the liner, if that makes sense. I think if I bend it around the liner, I would have the same trouble getting the top plate tight against it. If it's not clear from the pictures, I have to also have a horizontal plate to block off the top, that area flows into the chimney as well. Does that make sense? And once again, thank you for your responses, I really appreciate it.

Excuse my rough sketch, but this is kind of the thought I was having, of course it doesn't look easy to achieve though. The orange shows the overlap. The difficult part to get right is plate 2, since that back edge would be so rough.

 

[bholler]

Ah. So I had thought about trying that but unfortunately the liner goes back into that slot too far (its hard to tell from the picture). And the soot covered masonry slopes forward towards the liner at the top further reducing the clearance. So I can't get a flat plate back there unless I actually bend it around the liner, if that makes sense. I think if I bend it around the liner, I would have the same trouble getting the top plate tight against it. If it's not clear from the pictures, I have to also have a horizontal plate to block off the top, that area flows into the chimney as well. Does that make sense? And once again, thank you for your responses, I really appreciate it.

Excuse my rough sketch, but this is kind of the thought I was having, of course it doesn't look easy to achieve though. The orange shows the overlap. The difficult part to get right is plate 2, since that back edge would be so rough.

View attachment 255235

The flat plate will need to have a cut out for the liner. That is always how I do them in a situation like that

 

[maddog1016]

Ok. I had a hard time telling from the pictures then. Your original plan is probably what I would go with then

 

[farger04]

I suppose I could also try to flatten the edges of the masonry with mortar where the plates will touch. That my reduce the amount of caulk i'd have to use and get a tighter seal.

 

[bholler]

I suppose I could also try to flatten the edges of the masonry with mortar where the plates will touch. That my reduce the amount of caulk i'd have to use and get a tighter seal.

Just make your back plate big enough to get to where the brick are flat. Also you should try to get that elbow seated better into the stove

 

[farger04]

Will do. And I agree about the elbow, the liner is too tight to pull it down any more and I have no more leeway at the top of the chimney where it connects to the cap. I'm going to be installing a wind driven cap on top, so maybe I can add a bit of extension so I can pull that elbow down a bit and seat it better. Is there anything that can handle the heat that I can put around that elbow joint to seal it? It seems not great to have an unsealed joint right there, I could imagine a bit of smoke could escape and then go into the house, not to mention air from the house leaking out of it whenever the stove isn't in use.

 

[bholler]

Will do. And I agree about the elbow, the liner is too tight to pull it down any more and I have no more leeway at the top of the chimney where it connects to the cap. I'm going to be installing a wind driven cap on top, so maybe I can add a bit of extension so I can pull that elbow down a bit and seat it better. Is there anything that can handle the heat that I can put around that elbow joint to seal it? It seems not great to have an unsealed joint right there, I could imagine a bit of smoke could escape and then go into the house, not to mention air from the house leaking out of it whenever the stove isn't in use.

Smoke will not leak out the chimney is under vacum. It doesn't need to be sealed completely but that doesn't look right at all. It will allow allot of dilution air in

 

[farger04]

Ya that makes sense, dilution air would reduce the draft and cool the smoke before it leaves the chimney, so I wouldn't want that. I have been having draft problems, so that could be one reason. Once I get it more properly seated, would it be ok to put gasket cement around it for extra sealing?

 

[bholler]

Ya that makes sense, dilution air would reduce the draft and cool the smoke before it leaves the chimney, so I wouldn't want that. I have been having draft problems, so that could be one reason. Once I get it more properly seated, would it be ok to put gasket cement around it for extra sealing?

Yeah but it won't hold. Flat gasket works if there is a gap