ply floorboards

I've recently installed a floating floor over a concrete slab in a garden workshop. Due to height concerns (door threshold/plug sockets) I went for 25mm PIR under 18mm T&G OSB (with DPM and slip layers). I've got a lot more floor deflection than expected, would 3.6mm plywood laid perpendicular...

Hi, I want to tile the bathroom floor. Currently there are some very uneven floorboards (which are not very well supported in places due to bad notching). I could just lay the ply on top, but is there any reason not to rip the boards up first and just lay the ply on the joists? It would avoid...