chimney and hearth extension construction


Old 09-21-09, 05:53 PM
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chimney and hearth extension construction

I am in the process of constructing an old log house that I dis-assembled and reconstructed. I am currently building the chimney (solid brick inside and out) and the fireplace. The question I have concerns the hearth extension, during the chimney construction, when I reached the firebox height (which is approx. 6" not including the firebrick above the floor) I poured a solid 4" concrete slab with rebar from the back of the inside portion of the chimney to the outermost edge of the hearth extension. The firebox is constructed completely on the exterior of the house with only the hearth extension going into the house. The hearth extension is cantilevered whereas most hearth extensions are flush with the floor. The clearance from the subfloor to the bottom of the hearth extension is approx. 2". I had the local inspector come out the other day to approve my work only for me to quickly become confused when he said, "I am not sure about the hearth extension and having the subfloor being under the extension". He and I read the code book, which states, "No combustible Matl. is to remain against the bottom of a hearth extension after construction is complete". It does not say anything about not having sub flooring under the hearth extension. The distance from the front of the firebox hearth to the outermost edge of the hearth extension is 16" and distance from each side of the firebox to the outermost side edge of the extension is approx. 9". The dimensions are mandated because of the fireplace opening which is < 6. The inspector said he would have to ask his Boss if this would pass because of the liability. I do not want to have to cut off the extension I currently have in place and cut through the flooring if this is not necessary. I was also planning to build another fireplace on the 2nd floor using the same method as just mentioned for the hearth extension. Do you have any ideas or recommendations for a situation like this?
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Old 09-22-09, 06:23 AM
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You double posted, so I answered in the Brick, Masonry, Concrete forum. Mods may move it all here as it seems to be a better place for it.

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