cement board for hearth thickness

Old 12-07-05, 09:23 AM
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Join Date: Aug 2005
Location: Michigan
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cement board for hearth thickness

I am currently installing my hearth for a zero clearance fireplace. The manufacture indicates that the hearth be a minimum of 12 inches deep and made of a non-combustible material. In keeping with their instructions I will be tiling my hearth as well as the surround. They do not however instruct me as to the thickness for the non-combustible hearth. I have a 2x4 platform and plan on covering this with 1/4" cement board then applying a 3/8" thick tile on top, is this going to adequate or should I double the thickness and use 1/2" cement board?
Old 12-07-05, 10:06 AM
Join Date: Mar 2005
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cement board for hearth thickness

Do the instructions say the surface has to be non-combustible or the does the hearth itself have to be non-combustible?

It seems like a piece of non-combustible sheet aluminum over wood or any other combustible material would not be adequate. You are dealing with the possibility of burning material (800 -1500 degrees) sitting on top of a combustible (450 degrees flash point) hearth and not something as easy to achieve as a fire wall between house and garage that is intended to delay and not stop a fire.

You may want to check with the local codes also.


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