I am remodeling the bathroom and have taken the flooring down to plywood. The toilet is out and the flange is sitting there. I removed the screws to the flange and the (pvc) flange appears to be cemented to the drain. At least I think it is. Can I remove it? Should I be able to? How do I put wonderboard tightly under the flange or does it not matter?

 

I don't think you want to remove that flange. (I just added ceramic tile to one of my bathrooms and cut the tiles to fit around the flange with ~1/2 inch clearance.) The wonder board or whatever you're adding will add a little space between the bowl and the flange. If you think the new wax ring will not make a good seal with the new floor installed (bowl sits too far away from the flange), see if you can buy a thicker wax ring or some sort of extension.

Maybe someone with more experience could add something.

 

There is a wax ring that is used to seal the toilet to the floor. Carefully and slowly move the toilet and the seal will break free releasing the toilet.

 

Then a lot of shit will start flying all over the place j/k. Good luck with the project.

 

I just did this project successfully. I have a 1 story ranch so I ripped out all cast iron and went PVC because plumbing was totally exposed. If plumbing is not exposed forget it.

Post a pic so we can see where you are at. How much gap between collar and plywood right now? Rule of thumb = toilet's weight should not be supported in any way by plumbing (collar). Floor must do this so a flush fit is necessary. This was the hardest part of the entire bathroom remodel .

1)Flange height too high w/ ref to tile level you get "rocking" toilet that will eventually leak or worse - crack porcelain.
2)Flange height too low w/ ref to tile level you get gap between new toilet outlet and collar that wax ring cannot span which equals a leaker.

I have always ran tile "under" toilets (all the way up to but not under collar) so you need to consider that 1/8-1/4 inch height also.
Also, i used the Fluidmaster Wax-free gasket from Home Depot. Only $5 and it doesn't leak over time.

 

They make rings that fit over the flange that are about 3/8" thick. You can mount these to your existing flange with silicone caulk, line up the long slotted holes for the bolts that hold the toilet down. Make sure to clean the existing flange of all the wax and other crap that is on it before you put the silicone down. Use a PVC cleaner (usually sold with the glue) to do this. Cut your underlayment for a tight fit around the existing flange, then when you lay the tile cut them for a tight fit around the flange extension. You want to set the toilet on top of the tile, don't lay the tile to the toilet. Grout all the way to the flange, then install the toilet, after cleaning the floor.

BTW I am a Kitchen & Bath Remodelor, and have been in business for the last 11 years. Owner Eyeplay Renovations