We are in the process of having renovations done to our apartment and have had a contractor install new hardwood floors. The subfloor is a concrete slab and the floors were installed by floating them over a moistrue/sound barrier. In many places the floor are "soft" or move under our feet.

I have been told this is because the subfloor is not level. Is that the case or could it be poor installation? We pointed out a few spots to the contractor and it appeared they got slightly better, but there are a number of places that need work.

Because it does not appear to be an isolated problem, should we have him reinstall using another method? Glue perhaps? I plan to speak to the contractor in a day or so but would like to be a bit more informed before I do so.

Any advice on our options would be helpful.

Both of these are at fault, " subfloor is not level. Is that the case or could it be poor installation" The floor is not level and the contractor should have made the floor level before installing a somewhat rigid hardwood flooring. Shimming or better yet a pourable floor loeveler should be used to make sure there are no "soft spots"