I have a small 5 x 11 bathroom in 1961 coop/condo, wood subfloor (pictured) is not level. We don’t think water damage just building settling. This is a gut job, all fixtures being replaced. Would it make sense to use purlins then 3/4 plywood to level floor, then place new tub on new plywood? Or backer board & tile entire floor and put tub on top of tile?
Can’t put tub on joists or current subfloor as uneven. Can’t use self leveling compound as depth of pitch too deep (1/2 an inch or more).