I have a carpenter replacing my knackered upstairs bathroom floorboards with 18mm hardwood ply. He's kindly screwed an extra layer of ply underneath the area where toilet pan fixing screws will go, so that they have 36mm of wood to be secured in (plus the 4mm of LVT on top).
I've just been reading conflicting opinions though on whether toilet pans should be screwed to the floor at all though. My existing pan has screw holes each side which were being used before. I've seen some people saying the pan should be fixed down on the floor with mastic only, and the screw holes in the pan should be filled with silicon to prevent spills running through them and getting under the pan where they've nowhere to go. Also, if the screws were done tight enough to actually hold the toilet down absolutely rigidly with zero play at all, you would probably break the ceramic pan as you screwed them down that tight.
Conversely, I see others insisting you mustn't put any mastic or sealant around the toilet pan, and it should be secured with screws only.
I've just been reading conflicting opinions though on whether toilet pans should be screwed to the floor at all though. My existing pan has screw holes each side which were being used before. I've seen some people saying the pan should be fixed down on the floor with mastic only, and the screw holes in the pan should be filled with silicon to prevent spills running through them and getting under the pan where they've nowhere to go. Also, if the screws were done tight enough to actually hold the toilet down absolutely rigidly with zero play at all, you would probably break the ceramic pan as you screwed them down that tight.
Conversely, I see others insisting you mustn't put any mastic or sealant around the toilet pan, and it should be secured with screws only.