I thought I needed an airspace in the hearth, like against the combustible wall, but if they say the "open faced sandwich" of plywood, cement board, mortar, and tile is sufficient, then I believe that.
Very nice! One thing puzzles me though. If backer board and tiles are sufficient protection for the framing of the raised hearth, why not just remove the floorboards in the area and replace with backer board and tiles?
when your children are suffering from your punishment, tell them it will help them write good poetry when they are older. Like this tiny ad:
Quit your workee-job and live, year round, for free-ish in Montana