I ripped out two layers of linoleum flooring from my bathroom, and am ready to lay the porcelain 12x24 tiles (dry-fit done). The linoleum flooring had a paper underlayment, which was difficult to remove, so I left it down and planned to just tile over it.
A friend noticed and recommended removing it, unsure of what it is. From what I can find online, there are slight concerns of adhesion, but I tried a test piece of thinset, and it seems to stick better to this paper than it does to raw plywood.
The floor is a 3/4" OSB subfloor, then 1/4" ply, then this paper backing. I can't really tell what it is - it's not rosin paper (generally red from what I can tell, mine is grey). It's not tar-like at all, and it feels much thinner than 1/8", so I don't believe it's hardboard either. One answer I've found on this site seems to claim that it's actually a part of the old linoleum - I'm not sure about this From what I can tell, this bathroom was built in late 90's/early 2k's - I trust there's no asbestos in it, and I'm hoping the date helps with identification.
Can I lay tile onto this paper?