I just bought a house built in 1978 and I'm planning on putting tile in the bathrooms (currently linoleum).
The fixtures are removed and the flooring under the linoleum is particle board. I think its 3/4". It has a couple weak spots (one over a vent and the other around the toilet that was leaking).
I was planning on pulling this up and replacing with plywood and concrete backer board. However, my question is, can I put 1/4" backer board over 1/2" plywood, so that the level of the floor is pretty close to where it was before and not have a large transition between the rooms?
-edit to add-
1 bathroom is along an outside wall of the house.
1 bathroom is in the middle of the house with a support beam running along one wall (beam runs the whole length of the house).
Bathrooms share a wall in between them (total span of 10ft from outside wall to middle support beam of the house).
Both bathrooms are on the 2nd floor.
both bathrooms are above another heated/insulated room.
16in joist spacing.
I don't know how big the joists are because I haven't removed the existing subfloor yet.
We will most likely be installing ceramic tile.
My main goal here is to create the smallest transition as possible between the bathroom flooring and the carpet (installed on the same particle board) outside the bathroom.
If there are other options outside plywood + backer board that would be available, I am 100% willing to listen to them.