Hearth for Dutchwest Federal Airtight

[Jaina8851]

My husband and I just got an old Dutchwest Federal Airtight FA224CCL from a family friend. Our house has a chimney with no fireplace, just an 8" hole for a stove pipe. The floor in the room is laminate, and does not have a hearth yet, so we are looking to build one.

I have found a couple of the old manuals circling the web, but I want to make sure we make the hearth properly. One manual says K=0.84 and the other says 1/4" non asbestos mineral board will suffice.

We bought 1/2" wonder board and some slate tiles to put on top of it. Will this be a low enough K value? Is wonderboard mineral board? Should we track down micor? If we get micor, should we use both micor AND wonderboard? We do want to keep the hearth pad as thin as possible. Thanks in advance for the help, we just want to make sure we do this right.

 

[begreen]

Has this chimney been cleaned and inspected. You don't want to be connecting to an unknown chimney. There can be a lot of issues in some old flues such as multiple take offs, unsealed cleanout, unlined chimney, bad mortar, etc.. Make sure this chimney is in good, safe working order before connecting to it.

To meet the K value of .84 the hearth should have the equivalent of 1/2" micore 300 underneath the cement board. If you want to use Wonderboard only, you will need to use about 4 layers to reach this insulation value. Durock NextGen has a higher insulation value thus it would require 3 layers.

 

[Jaina8851]

We do have a chimney inspection scheduled. They will be looking at the chimney as well as the stove for us.

So the construction "sandwich" should be plywood, micor, and then wonderboard, with the tiles on top? If the micor is doing most of the work for the K value, could we get away with thinner wonderboard on top?