Do you have mortar under the tub for support? It would definitely require it in this situation. If only supported by shims like that, you will have problems with the tub flexing and moving down the road. Caulk joints will constantly need redone, and most likely you will hear creaking noises when walking in
Yes, porcelain tile. That’s a solution! Thank you. Instead of backerboard, could I do 1/4 inch plywood? Wouldn’t I get the same result? I still have to fix that raised lip anyhow, so if I still cut out that part of plywood that is raised, replace that piece, then lay 1/4 inch plywood over top, opposite direction, I can fix both problems, correct? (I feel like there was a tad too much space between plywood sheets, so laying opposite direction will solve that as well.) This was mine:
A regular sheet of 1/4″ plywood can be problematic. I have seen issues where after tiling over the regular 1/4″ plywood, areas can lift and create cracked tile. The shrinkage of the thinset can peal or pull the plywood from the original subfloor.
I went with the 3/8 cdx plywood, over top the now fixed 3/4 inch plywood sub floor. What’s the best way to fasten it down? Glue? Nails? Screws? Combination? I am afraid over time, nails will pry up. I have 16 gauge 1 inch nails/gun. Deck screws don’t come in 1 inch that I know of. I want to avoid at all costs, the original screws I used to fasten the sub floor to the joists, those caused me a lot of problems.
I don’t blame you not wanting to use those wood screws for this!
Gluing and screwing would be the best method, but gluing and nailing would be adequate. I personally always end up nailing and never had an issue. Much faster that way. But I do use a framing nailer…..not a trim gun.
If you do use screws I would still use deck screws. they have them in 1 5/8″. A bit longer than you need them….but shouldn’t hurt anything