I'm in the middle of a bathroom remodel, planning to put ceramic tile on most walls plus floor. I have a few inches in front of the shower which I was going to use to create a wider "threshold" into the shower, using the extra width to place a (swinging) shower door.

Anyway, the existing shower pan is 48" wide and 34" deep and the entry threshold is about 4 1/2 " high by about 2 1/2 inches deep. I've already installed (three) 2X4's one over the other, to widen the threshold by 3 1/2", so now it's about 6" wide. I want to tile over the whole threshold using the same floor tile, so the top piece will rest across this threshold, 2/3rds will be on the 2X4 extension, then the other 1/3rd will be setting on top of the plastic portion.

The question is, can I use thinset on both the wood portion and the plastic portion, or should I get a mastic to use on that part?

Thanks in advance

 

No. Not in either case.

 

OK.....any other workarounds?

How about attaching a piece of cement board first to both of these, screwed into the wood part, adhesive over both, then thinset, thoroughly caulked along the edge facing the shower of course?

 

Don't have a good idea for what you want to do. The tile wouldn't stay with the plastic very long and you don't ever want to apply tile directly to that type of wood either, it also won't last.