Home > How To > Interiors > Q&A: Backerboard: Which Side Faces Out? Interiors Q&A: Backerboard: Which Side Faces Out? Is Steeper Better? By Hank Spies Login or Register to download the PDF version of this article. (84.08 kB) A. Backerboard is usually installed rough side out when used under a thin-set mortar for slate or ceramic tile flooring, and smooth side out when it is a base for adhesive-set wall tile. Login or Register to read the full article.