I've seen a couple posts on this topic on here so I'd try my luck with my situation. House built in 1860 with a 1940's addition. In the original house, the second story has beautiful 9' ceilings. The addition however is complete crap. The ceilings are 6'6". The attic in the addition is taller than in the original. The roof lines (gable roof) are the same and same construction style as the original.

Would it be possible to pull the floor up in the attic and the ceilings in the second story addition without messing with the roof? The weight of the roof is carried by the exterior walls. I don't mind if the walls have angles towards the top. I'm 6'4" and would like to be able to have a ceiling light without ducking.