I received varied responses on this question in other forums and ended up staying on the side of caution. I heard stories of the floor giving way, walls separating from floors and others with no problems at all, while others shored up the flooring. It also mattered whether the tank was not parallel to the beams, but accross them.
My tanks are no larger than 30 gallons and sit along walls where the beams are. They are freshwater, so they don't have the added weight of rock and coral. A basement floor would be best for larger tanks, in my non-expert opinion. Here is a link to give you some ideas about weight. Maybe you could find information on the weight bearing properties of laminate flooring. I'm thinking the weight would leave some type of impression, at the least.
http://www.alysta.com/books/fishtank.htm