Our house was built in the early 70s when in the south it was common to have a sub-floor out of plywood and the next layer was particle board. The walls of the house were built on top of these two layers. Now almost 30 years later we want to install ceramic tile. We've scraped up the three layers of vinyl flooring and are to the particle board (with some glue/backing attached in spots around the kitchen/diningroom floor). Of course, we've already bought ceramic tiles ($$$$) and new kitchen cabinets ($$$$) and have been to Lowe's and Home Depot with nothing but different suggestions to our problem! My husband builds wooden boats (as a hobby)and wants to put the resin he uses on his boats to seal the particle board. We know when the moisture of the thin-set is put on the particle board without it being sealed, we have even more problems. My question is: Can we even seal this particle board, or should we replace it with plywood? The problem with removing it is that it is actually underneath the walls and very hard to DIG out of there. What to do? I have tried to E-mail some of the ceramic tile folks and only received a CUTE E-mail is response. Surely there is some kind person who can give me suggestions. I hope there is someone out there who has a 30 year old house with this same problem...maybe even already corrected it. Please give me your thoughts. Many, many thanks!!