# Lining a fireplace with granite?



## cauldronfarm (May 24, 2012)

We're adding an extension to our house with a new dining room, and we are putting in a fireplace. I have read the building code until my eyes are crossing. It's going to be a Rumford fireplace. What I'm curious about is this:

When I read about building fireplaces, all I ever hear about lining the firebox with is firebrick. We happen to have a thigh-hile pile of huge 1" thick slabs of polished granite, salvaged from a granite countertop business that went out of business and abandoned its "scrap" on the street. It is lovely stuff, and, I would think, fireproof. (We've used small slabs of it to build small fires on in the woods.) Also, we are trying to keep down expenses, and firebrick is expensive, and the granite slabs are free and lying in our yard. We have a diamond saw to cut them.

Is there any reason, safety or otherwise, why we should not use them to line the fireplace? Building code just says that if you don't use firebrick, you increase wall thickness from 8" to 10", which means 9" with the granite, and bricks never line up to 8" anyway. So we could legally do it. Does anyone know about, or have any experience with, lining a fireplace firebox with granite?

Thank you!

-RK


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## Crane Stoves (May 24, 2012)

Ive certainly seen many granite fireplaces and chimney's which have stood the test of time a whole lot better then brick! Usually I see them built with "cobblestone" type granite (sometimes rounded exterior faces, sometimes "stepped" in some fashion for a decorative appearance). It always seems to be homes built in the 1900-1930 era which have these called "arts and crafts" or Craftmen style or bungalow's or frank llyod wright   type homes. I have not seen countertop granite used to build a liner or fireplace or chimney but i have seen it used successfully to build an outdoor "pizza oven" style fireplace (i will try to stop back at the home this was done at over 10 years ago and snap a shot).

So to finish my post i would say im pretty sure granite is granite anyway you cut it!


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## Wood Duck (May 24, 2012)

Sorry I don't know what a Rumford fireplace is, but in general fire bricks are meant to insulate the firebox. The question is whether granite has similar insulative properties as fire brick. Granite won't burn or degrade from heat (granite is formed at very high temperatures), and as long as it doesn't crack too easily the only thing to ask is whether it provides enough insulation.


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## Ashful (May 25, 2012)

To expand on what Wood Duck is saying... you don't just care about the durability of the granite, but it's ability to insulate surrounding wood structure from high temperatures.  I have only owned one all-granite fireplace, and it was an outdoor fireplace.  It cracked thru during one very hot fire, but the crack propagated along mortar lines, and not thru the stone itself.  It was rougly 55 years old, at the time.


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## jeffesonm (May 29, 2012)

I bake bread and am often looking for cheap, heat resistant materials to use as a baking stone.  Some claim that certain types of granite can emit dangerous gasses when heated which is why they are not recommended for baking stones.  Don't know any more specifics but it's worth investigating.


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## clr8ter (Jun 3, 2012)

The problem, I believe, is that certain stone contains water. Heat it, and it could turn to steam, and fracture the stone. Granite in our area,  New England, also contains Radon, or so they tell us. My buddy built an outdoor fire pit out of granite that is usually crushed and used to build roadways. After not too many fires, the stuff cracked and somewhat disintegrated. I would NEVER build a chimney out of something like that. Are those old stone fireplaces fireboxes lined with that stone, or brick?

For my money, I'd build a nice hearth and mantle, use that granite, and put a wood stove there instead. Fireplaces are so inefficient, even the Rumford ones.....


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