Wonder board? Cover with sheet of stainless steel?

[jdrury245]

OK, I have a pre fab fire place that I constructed myself last year. I have rock on the out side. But, I have no rock on the inside. I only have wonderboard with the seams sealed. I have a Castile insert placed inside this prefab fire place ( the castile is surrounded by its own built in firebox). I have followed all clearances and I have had it inspected (it passed). I also have already burned for a year. My concern is that the wonderboard is not fireproof enough. Should I line the inside with sheet metal? Let me know your thoughts?

PS - I took a scrap piece of wonderboard and took a plumbers torch to it to see how it would burn. Only the edges on the out side of the scrap caught on fire but then quickly went out. everything in the center of the scrap did not burn just turned brown. These seams of course are sealed with mortor in the pre fab.

 

[begreen]

If this is true Wonderboard brand cement board it should be non-combustible. How far is this surface from the Castile sides and top? If all clearances have been honored, it should be just fine. You can cover it with metal or stone for cosmetic reasons. Just don't use a combustible like glue to do it.

 

[jdrury245]

Thank you for your reply. Back 3, top and sides more than 6 inches. Since you can not see the wonder board on the inside, I was going to cover the back of the pre fab with sheet metal as an extra precaution. My test proves that wonder board will not combust and spread. But, the sides were the nylon is sticking out is the only part that catches but quickly goes out. I might just go ahead with the sheet metal? Sent from iPhone.