Building a hearth pad

[john26]

I need a hearth pad with an R vaule of .84 to lay on top of a hardwood floor. I have a raised hearth about 20" insert sets back 12". I would like to make a pad with ceramic tile on top what would be a good underlayment material? I was thinking 2 layer of 5/8 Durock

 

[begreen]

What stove is this for? Are you sure this is the R value requirement and not the K value? Just to verify, is this for a hearth pad extension at floor level to the existing fireplace hearth?

 

[john26]

Its for my napoleon 1401 . Sorry yes you are correct it is K Value here is what the manual says
HEARTH EXTENSION / FLOOR PROTECTION: Must be non-combustible and extend in front of the insert and 8" (203mm) on both sides with a minimum thickness of 1/2” (12.7mm) and a thermal conductivity factor (K) 0.84.
And yes it is for a hearth pad extension at floor level.

 

[begreen]

Yes, .84 K for 1/2" millboard is a common spec. The example they use is for floor protection with a hearth at floor level. I strongly suspect that all you will need is ember protection for this extension, due to the 20" hearth height. There will be little radiant energy at floor level from that height. It would be good to contact Napoleon support to verify. If so, all you would need is a simple metal sheet or panel.

 

[john26]

Would a fiberglass fire retardant rug work for ember protection?

 

[begreen]

Would a fiberglass fire retardant rug work for ember protection?

Though better than nothing, it's not really proper. The protection should be at least semi-permanent, meaning attached to the floor so it doesn't move around.

 

[john26]

Called napoleon there recording said call a dealer LOL. So I called a local dealer they said it just needs a non combustible solid material no rugs. I am either going to lay down a piece if granite or ceramic tile on backer board.

 

[Supersurvey]

I often wonder about the joint between the hearth and the extension. Do you just but them together?

 

[begreen]

I often wonder about the joint between the hearth and the extension. Do you just but them together?

It's ok to butt it tight to the hearth. If the hearth surface is very irregular then the gap should be filled with a non-combustible caulk like silicone.