I have a 40+ year old house. The problem I have is that most of the joists have bent inwards from age, the original builder made huge mistakes, hence the problem. Either way the result is that my floors on both levels are "wavy". I have heard there is a self leveling compound or leveling compound that's fairly light when applied and could be used to level my floor, however I do not know the name, neither do I know if it really exists. Using the leveling compounds that are offered at Home Depot or Rona are a big no no as these are concrete based and are extremely heavy when applied over large surfaces.
If there is no such thing, what are my other options?
Any help, suggestion would be great.