Bottom of hearth pad.

[knotdodger]

My R-value needs to be 0.8. I have .25 in of slate existing that is 8ft wide
by 5ft deep. I want to build a Portable hearth pad to put down on top of the
slate. If I place the micore 300 first , then the one layer of durock. Is the bottom
of the micore going to get messed up??? The slate is not exactly flush with each
other. Or should I place one durock, one micore, and one more durock????
Bond them all together with thinset then tile and call it good???

 

[edthedawg]

Yes you should put something under the Micore.

Assuming you get to the min desired R-value w/ the top tile, durock, and Micore layers, you can put pretty much anything underneath the Micore. I had a flush tiled hearth inset to fir hardwood flooring. My "non-permanent" hearth sits on all that - I used 1/4" hardi-backer as the bottom layer.

Good luck!