Hi we just installed ceramic tile on our floor. We were lucky and it was on a concrete base. My neighbor that has a split entry house was not so lucky. They told her the same thing about the screws and withing 6 months the screws were backing out and lifting the tiles. She had another contractor come in and remove the tile and the partical board. They then laid a masonary board which is more stable. It has been a year and there is no cracking or lifting of the tiles. Just remember to seal your grout after a week. It is no fund to scrub and reseal on your hands and knees.