Hey, the only benefit to going to a comercial gym is the eye candy. Might as well get an eye full!

I can tell you that if the concrete slab was poured correctly, that you probably wouldn't do much damage with a barbell. Though it wouldn't be the worst thing for them to get some rubber mats. I know my old gym had a platform area (you know, because you need three layers of half inch plywood and a layer of half inch rubber for curls) and some little chunks of rubber mat for work outside of the platform. Not to mention the entire DB area was rubberized. In the end it would be the weights I would be more worried about than the floor. dropping a bar on concrete could potentially bend the bar, or crack a crappy iron plate. Still, the floor should be fine. I drop my 260lb concrete atlas stone on a 1/2" rubber mat and onto a crappy old brick and mortar floor (big bricks, not little... my garage is ancient) and other than cracking the mortar a bit, there is no real damage. We are talking a full drop from 49"... way higher than you would drop a DL, and a single point of impact. All things being equal, I think Mr. Gym guy was just being a prick. Maybe your sis shot him down on his last attempt at her goodies?