Hi. I am waiting for my PE T5 Alderlea to be installed later this month. Instead of the recommended hearth pad our installer recommended (Graysen 54x54" ceramic pad), I've decided to construct a tiled hearth pad that'll compliment the tiled fireplace surround I will be installing. I've read a lot about r-values needed for hearth pads, but the only specification the T5 manual gives is for a non-combustible ember protector. Am I correct in my understanding that all I need is an adequately sized tile pad (or similar non-combustible surface), but that r-value does not apply to this application? If so, I plan to screw a sheet of durarock to my osb subfloor, face it with aluminum trim and tile directly over the durarock. Thanks for the feedback.