I am starting to plan for tiling our ktichen floor. We currently have linoluem on the floor. This home is 80 years old. The original sub-floor is soft wood and then there is something that has been hammered over the soft wood. I know that I can rip off the edging or room dividers when I get closer to getting started to find out what the 2nd. layer is, but I thought I would ask if there was a typical sub-floor that would have been put down in the past 20-40 years for a linoleum floor??? Could I be LUCKY and this be cement backerboard???AND, I know if it's not cement backerboard, I need to put that down for the tiling. Is it best to put the backerboard over the 2 levels of flooring, or rip up the one level of sub-floor and then put the cement backerboard directly over top of the soft wood floor??? Thanks.