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?
We must storm this mad man's lab and destroy his villanous bomb! Are you with me tiny ad?
Escape to gardens and natural buildings (for free-ish) in Montana