Our contractor is installing our Kohler/Sterling tub. I don't think he has intentions to level it and said to put felt underneath the tub. I've been reading a lot of comments on here as well as others on Google, and everyone says to use a mortar bed. Has anyone ever heard of putting felt under a new tub on the plywood?

I mixed a bucket of mortar, poured a pile in the center of the tub space, and set the bub down into it.. leveled it off and let it set to dry. On both my bathroom. One was on concrete the other on a an upper level plywood sub-floor.

Its meant to be a central point of support for the tub, which with you and a lot of water in it is significant otherwise you will likely have caulking issues or worse down the road. Lighter built tubs WILL flex and crack without it.

THe ones I've seen the bottom of the tub will NOT rest on the floor as the skirt is longer putting all the weight on the edges and the skirt.

Kohler/sterling tubs have VERY specific bedding substrate instructions...some tubs need to be supported using structolite perlited gypsum plaster, others need a plaster or mortar bed and yet others are required to have adhesive caulking join the ribs of the tub to the floor. As you suspected, installing a felt bottom is not common practice!

Contact kohler directly and ask the tech. support department what should be done with your specific tub, OK? Here is the contact info.:

18004KOHLER

The warranty on the tub is voided if the tub is not bedded per instructions!

You could also search out the exact installation guide for your tub if you know the model name. Check for it at: www.us.kohler.com

Good luck!

Mark