Redoing bathroom floor. After removing tiles and underlayment and linoleum, the floor that's left is decrepit, uneven, wavy, has some old plumbing holes. It is not rotted though, the wood is sturdy.
I'm going to use Ditra.
With Ditra, is it necessary to have a plywood underlayment, or can I just install right over the floor as is (covering up the holes of course) and the thing will even itself out?
Barring that, if I do need to install a underlayment, can I use 1/8 plywood?