Toilet Flange Extension Help
 

Installing a new toilet over new tile floor which we put in over the old tile. Purchased a flange extension to cover the added height. Do I need to put sealant between the old flange and the new extension? Any other advise on this install would be appreciated!

Is the existing flange a plastic flange?

I sometimes double the wax gasket when concrete board and tile is layed after i have the flange in place. I put down the regular gasket first then the improved gasket with the rubber funnel like flange on top of that. Longer bolts can be purchased too. Ive never seen the extension peace you speak of but i would use some silicone or gutter and flashing sealent between the two.

Some extender flanges have an adhesive on them, others don't. If I were installing one without the adhesive, I would apply silicone caulk between the new flange and the original. The Extender flange also needs to be screwed down to the floor using the 4 holes matched up with the holes in the old flange.
Note: Just read your reply and I would not use plumbers Putty as it is not made for "running" water. A larger wax seal is better than using two seals since many times, one seal will slide during installation and block the drain.

Flange Extension
 

The existing flange is plastic and the extension (aprox 1/4" high) is also. Been told plumbers putty between the two parts will ensure a good seal. I also have an oversized wax ring. I DON'T WANT ANY LEAKS!

Clean existing flange real good, apply silicone between the new and existing flanges, the screw them together with non corrosive screws.

What MJ said.