Every once in a while I come across to an attic that has been remodeled but hasn’t been remodeled correctly. The homeowner looks up in the attic and realizes that there is enough room for a new bedroom and possibly a bathroom. They don’t realize the structural problems that they’re about to encounter or the problems that could be passed on to the next homeowner. Most ceilinged joist aren’t designed structurally to carry the load of a floor and that’s actually why they’re called ceiling joist instead of for joist. Even if you install larger floor joist, the building foundation might not be strong enough to carry the additional weight that’s going to be provided by the new room. It wouldn’t be a bad idea to contact a structural engineer, instead of a contractor, if you’re seriously thinking about creating a new room or remodeling your attic. Contractors that are hungry for work can usually fit your budgets into their contracts and this might not benefit you or your family. If a contractor tells you that your new room can be built on top of your ceiling joist, I strongly suggest that you go back to my first suggestion and hire a structural engineer.