Can this rubber tile be direct on top of hard wood floor? Is it safe to use a 300 lbs power rack? If not, do I need extra layer in between?

You can install our 8mm Strong Rubber Tiles directly over hardwood flooring. These tiles are the same as the rolls that we used in the Biggest Loser Gym, so a 300 lb. power rack will be just fine on this floor. If you did have any concern about the rubber flooring staining your hardwood flooring, you could place a plastic sheet between the rubber and wood, but this is not necessary for most installations.