Ya know, that fireplace might not be rated by the manufacturer for an outside application as pictured, But! I personally just don't see much of a problem. Heck it is sheltered by a large roof line and it is in the high desert of Nevada. I bet that it sees more moisture from the combustion process than from rain. Yes, I understand the warranty, etc, etc, is out the window.

As for the mantle, I can't find anything that say it is not allowed to be that size.

You can backup whatever you say about the fireplace but you will have a difficult time with the mantle I'm afraid.

If it was me I would note that the FP is not rated for this type of installation and that any manufacturer warranty is voided. That is about all that I might say. Without seeing the entire house, age, condition, etc, it is hard to render an opinion.

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Scott Patterson
Spring Hill, TN
http://www.traceinspections.com