: I am remodeling a bathroom that required the installation of a new subfloor. I will be installing 1/4" Durock on top of the floor before installing the ceramic tile. I assume the new flange should be mounted to the plywood subfloor only, but should I mount the toilet bowl to the subfloor (cutting the Durock around the toilet base), or should I put the toilet on top of the Durock, which would then have a hole cut just around the flange?

The toilet sets on the "finished" floor.
Wait until the tile is laid and grouted before setting the toilet. Terry

: Also, I have heated up & removed the cast iron flange from the 4" COPPER waste pipe it was soldered on to. Do I want to solder on a new iron flange, or is there a good friction fit flange that will work well on copper pipe? I want to stay away from "leadding" the flange, if possible!

If you have acces to the waste arm, you can use a mission style plastic x copper coupling and adapt to plastic from the copper pipe. Terry