It's been an issue for a while but big difference between one person in the family and a family of five who never stay still.Really depends on the type of flooring. If it's 'floating flooring' for instance.... might need some boards replaced. Laminated flooring laid on top would make no difference (as you've discovered!)
I doubt it's something that would be cheap to fix, if it's really a physical building defect.
Since the problem only arose with the present occupants (if I recall correctly) I'd say the flooring isn't really the issue, it's the occupants.
Laminate flooring is frowned upon in many buildings with neighbours 'downstairs' because it basically turns the floor into a feckin drumskin.
I'm no expert but think you're probably right there. Just going on advice given from someone else perhaps not as clued up.It will be floorboards, no the joists. The joists are usually solid between up and down houses. Probs been rewired or the heating done and the lifting boards no put back down right.
The way I see it is this really shouldn't be my issue. Does anyone think maybe gaining some legal advice in the matter would be worth while? Obviously you're obliged to make sure your home is in reasonable condition as part of your homeowner agreement as this clearly is not.