I'm remodeling my kitchen and den and have found out that I need to remove a 1960's tile and vinyl before installing durock for a ceramic floor. I've discovered a "black mastic" substance on the subfloor. I know that it has to be removed. Is it going to be more cost effective to remove the current subfloor w/ mastic and replace it with a new subfloor? Thanks ahead of time.

thanks for the advice