# Greetings-- Firebox repair?



## anita42 (Jan 13, 2010)

Hi, I'm Anita and I live in northern Florida where it's been below freezing every night for the last few weeks. (Which wouldn't be that big of a deal if our heating systems here were designed to handle it, but they're not!)

I am looking for a little advice on repairing masonry fireboxes. 

I have an old house with a fireplace which I do not use because the chimney is unlined and the firebox not in good shape.  I have been mulling over what to do about it.
Originally I was thinking mostly of ambiance, but the recent cold spell has convinced me I should try to get something in there that can produce a bit of  auxiliary heat when needed. 

I think I would like to block off the chimney with a metal plate as described here: https://www.hearth.com/econtent/index.php/articles/making_a_block_off_plate/
Then I would like to have a small set of vent-free gas logs installed. (Small enough to fit in the fireplace and to not fry the wood mantel)  The room is plenty big enough so it would not be a "confined space" according to regulations for ventless appliances.


The mortar in the firebox is crumbling .   Can fixing this be a reasonable DIY job?  How would this be done?  I assume I would scrape out the loose mortar and replace it with refractory mortar?  Any tips on how to do this so the new mortar will "stick" well and not spall off with the first temperature changes?  I retiled an entire bathroom last summer so I have some experience with this sort of thing. 

Thank you very much. 

A.


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## begreen (Jan 13, 2010)

Welcome Anita. A block off plate is only used in conjunction with a sealed system that assures the flue gases are NOT in the fireplace firebox. It's not for an open fire, wood or gas. An example of a sealed system would be an insert or freestanding stove that has a flue liner from the stove to the roof.

One thing you want to be careful about is doing a surface cosmetic fix to the masonry that hides underlying issues. Best to have a professional sweep and perhaps a mason to examine the current fireplace and flue for an assessment of the issues and cost of fixes. They you will be able to make a decision on the safety of the system and whether some of the fixes can be done by doing it yourself.


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## anita42 (Jan 13, 2010)

BeGreen said:
			
		

> Welcome Anita. A block off plate is only used in conjunction with a sealed system that assures the flue gases are NOT in the fireplace firebox. It's not for an open fire, wood or gas. An example of a sealed system would be an insert or freestanding stove that has a flue liner from the stove to the roof.
> 
> One thing you want to be careful about is doing a surface cosmetic fix to the masonry that hides underlying issues. Best to have a professional sweep and perhaps a mason to examine the current fireplace and flue for an assessment of the issues and cost of fixes. They you will be able to make a decision on the safety of the system and whether some of the fixes can be done by doing it yourself.



Hi, BeGreen.  If not a block-off plate, what could be done to keep the heat from escaping out of the chimney (using ventless logs)? There is no damper.  (To be clear, I was thinking of a block-off plate with no hole cut in the middle.)


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## begreen (Jan 14, 2010)

I can't answer that one. As noted, this is not the intent of a damper block off plate.

 From what I've read, unvented gas logs are not a good idea. Can introduce a lot of moisture into the room which can start mold issues. Also can deplete oxygen so they require opening a window which defeats the blocking of the chimney. 

Moving to the gas forum for more help on gas options.


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## DAKSY (Jan 14, 2010)

https://www.hearth.com/econtent/index.php/forums/viewthread/50286/


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