# Removing new brick from within hard mortar



## JBM (Mar 31, 2011)

If you fill your chimney solid it will develop a crack or cracks. I fix dozens of chimneys every year with issues of being to solid around the flues in woodstoves, fireplaces ect. A 12x12 flue can expand as much as 3/4 of an inch and all the cement in the world (inside the chimney ) wont keep it from doing so. 

We now put partition walls inbetween each flue keeping them nestled in place so to say. 

Although when you read the code it is incorrectly stating that 1 or more flues require a 4" partition. 

They have mis interpeted the definition of "flue" as in the old days the brick chase itself was the flue, and yes, if there was 1 or more it needed a 4" wall. 

The people who sit in round rooms and come up with this stuff do not know their history,

in my humble opinion of coarse.

Although a 4" wall is a better built chimney, but thats not the point. A 8" wall with steel and rod is even better. What about ibeams, that would make it even better. See my point.

Anyways, carry on.


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## artisanstone (Nov 27, 2007)

heavyc said:


> Did I read post right? You leave an air space around flue? We set our flues with fire clay to prevent burn out. We then leave an inch or better around flew as we fill chimney, slush said void in mortar. Standard practice in up state N.Y. where I grew up and also here in the south were I now reside. The only air space requirements are distance of chimney away from all framing/wood of the home structure. Approx 4 feet from cap we install a rubber membrane to prevent water intrusion.


Fireclay mortars are also not to code per IRC. Where in the South do you reside?


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## heavyc (Jul 2, 2013)

The link fjn provided does say fire Clay recommended but not necessary. Sandhills N.C. I also noticed in Cali they use the method we have used for years with re-bar enforcement. The mortar encasement of flues has to do with potentials for earthquakes.


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## dom-mas (Nov 26, 2011)

heavyc said:


> Did I read post right? You leave an air space around flue? We set our flues with fire clay to prevent burn out. We then leave an inch or better around flew as we fill chimney, slush said void in mortar. Standard practice in up state N.Y. where I grew up and also here in the south were I now reside. The only air space requirements are distance of chimney away from all framing/wood of the home structure. Approx 4 feet from cap we install a rubber membrane to prevent water intrusion.


What's the point in a flue liner if the air space is full? The flue liner is there to stop the heat transfer to the masonry units. Tough to do wihout an air space. Just because code doesnt require it doen't mean you shouldn't do it


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