Using Ceramic or Carpeting Over Luan Plywood (Subflooring)
How to Bend Plywood
If you have wood floor of different widths and lengths compromised of two layers. Each layer should act independently of each other in regards to how it constracts and expands. If you might have noticed, hardwood on a wood surface will expand when it's humid and shrink when it's dry or hot.
Luan Wood Video Series
Bending Luan Wood Video
Installing Luan Wood Video
Cutting and Installing Vinyl Over Luan
Installing Luan Over Subfloor
Laying laminate over Subfloor
Making Tile Flush With Subfloor
Attaching Luan To Subfloor
Working With Luan For Do It Yourselfers
Replace hardwood with Exterior Glue Plywood with the minimum thinkness of 3/8's of an inch. Fasten according to APA guidelines, and then from this point on you can use either an uncoupling membrane or install the tile directly to the plywood. The cost of uncoupling the membrane will be money well spent, as you will find.
Using grout sealer will not make the subfloor or the ceramic waterproof, the only purpose of the grout filler is to reduce the effects of staining.