Construction of raised hearth extension

[Alagar]

Hi, I am getting ready to install a Superior WCT6940 / Astria Montecito Estate and am wondering how to properly construct a raised hearth extension such as is seen in this image from the manufacturer's webpage:

Below is a copy of the manufacturer's instructions for hearth construction, but it depicts the hearth extension extending out flat from under the fireplace whereas I would like to raise it up as shown by the red box and then add a hearth stone of some type across the top as shown by the blue box.

The instructions require at least 1/2" non-combustible material below the fireplace and at least 1" cement board below the tile they depict on the flat hearth extension. What do I need to do to raise the hearth extension height by about 6" so that the hearth ledge is just below the fireplace front façade?

Any help or suggestions are greatly appreciated.

Thanks!

 

[bholler]

Hi, I am getting ready to install a Superior WCT6940 / Astria Montecito Estate and am wondering how to properly construct a raised hearth extension such as is seen in this image from the manufacturer's webpage:
View attachment 302070
Below is a copy of the manufacturer's instructions for hearth construction, but it depicts the hearth extension extending out flat from under the fireplace whereas I would like to raise it up as shown by the red box and then add a hearth stone of some type across the top as shown by the blue box.
View attachment 302071
The instructions require at least 1/2" non-combustible material below the fireplace and at least 1" cement board below the tile they depict on the flat hearth extension. What do I need to do to raise the hearth extension height by about 6" so that the hearth ledge is just below the fireplace front façade?

Any help or suggestions are greatly appreciated.

Thanks!

It looks to me like if you raise the hearth you will be covering the bottom vents

 

[begreen]

It's a good question. The manual doesn't directly address this. Instead, it talks about the hearth extension at the floor level. The picture looks like a studio shot with the fire or the whole stove photoshopped in. I would call Astria on this one. My gut tells me that I would want more insulation than 1" of cement board, but how much?

 

[Alagar]

The vents are towards the bottom of the façade and then there's an additional 6" below the bottom of the façade to the bottom of the fireplace that is just plain sheet metal.

I'll try contacting IHP and see what they say.

 

[begreen]

Yes, I see what you want to do and reviewed older Lennox and BIS docs for this insert, but no additional info was found. If they are no help I would at least put a 1/2" layer of micore in between the cement board sheets for peace of mind.