Sealing up an old thimble hole

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feno

Member
Apr 25, 2020
8
Hillsdale NY
Hello all,
In continuance of all your great advice, I have another question for you all.

I recently purchased a house to turn it into a long term rental.
It has a new oil furnace in the basement and I'm replacing all the old hydronic slant/ fin baseboard heating units in all the rooms. It had a very old gas stove upstairs that has just left a hole due to a cracked and deteriorated thimble. I'm going to brick up the wall where this was and put an electric unit there, as:
1. Wood or pellet isn't desirable in a rental
2. Renters aren't going to foot a gas and an oil bill.

So, this is my problem, I have the hole there, that I was going to cement and brick cement up, but am wondering how I should go about sealing the clay liner first, before motar application?

all assistance is appreciated from you guys, see attached picture

thanks

image0.jpeg
 

Eman85

Feeling the Heat
Oct 10, 2022
482
E TN
Break up some brick and lay them in the thimble with mortar and then cover it all with brick
 

Ashful

Minister of Fire
Mar 7, 2012
18,087
Philadelphia
If any future use of that flue will rely on the installation of a liner, then just break out the thimble and brick up the hole. But if you have some desire to leave an otherwise useable clay-lined chimney, you'd better consult someone like @bholler.

I have at least four bricked (or stoned, or plastered) over thimble holes in my house, which I've discovered or made aware by prior owners so far. I'm sure there are more, covered and camouflaged too well to easily see. But my chimneys are too old to contain clay liners, they're bare stone themselves, and all present use of them is as a simple mechanical chase for newer stainless liners.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
31,105
central pa
Hello all,
In continuance of all your great advice, I have another question for you all.

I recently purchased a house to turn it into a long term rental.
It has a new oil furnace in the basement and I'm replacing all the old hydronic slant/ fin baseboard heating units in all the rooms. It had a very old gas stove upstairs that has just left a hole due to a cracked and deteriorated thimble. I'm going to brick up the wall where this was and put an electric unit there, as:
1. Wood or pellet isn't desirable in a rental
2. Renters aren't going to foot a gas and an oil bill.

So, this is my problem, I have the hole there, that I was going to cement and brick cement up, but am wondering how I should go about sealing the clay liner first, before motar application?

all assistance is appreciated from you guys, see attached picture

thanks

View attachment 301524
Is that flue used for anything else? Technically to close off the liner it should be firebrick and refractory mortar
 

feno

Member
Apr 25, 2020
8
Hillsdale NY
Ok i got it, thanks all, i have a double flue chimney, one is being used for oil boiler ventilation and this was just for the old gas stove.
I’ll remove the half bricks where necessary and insert new full bricks and remotar it all to create a solid wall agains the hole in the clay flue.
 
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