Hey guys, so I'm mid-renovation on my home and have hit a bit of a stumbling block. Basically my house is a two story, but the entire 2nd story has been converted out of attic space (my guess). The second floor is built on 2x10s at 24in spacing that meet the top of the second story walls and serve as ceiling rafters for the first floor, and (i assume) cross ties to keep the roof from collapsing outward. My project is to rip out one of the 2nd story walls (parallel to the roof line) and add a railing for a loft style overhang over the first floor - featuring a cathedral ceiling which follows the roofline from the wall up to the top cross tie. I dont know if it's important, but the second floor is also supported by first-floor walls it seems. Above the second floor, I have also noted 4ft long cross ties which also form the top of the ceiling for the 2nd floor. The roof rafters (long boards that create the roof line and support the roof decking - sorry if I got the term wrong) are long 2x4s. I am already planning on adding 2x10 rafters along side the 2x4s to create a larger insulating space, probably not with a continuous board though. My questions: Am I detracting from the strength of the roof by doubling each 2x4 with 2x10 segments? Should I even be concerned with the strength of an approx 13 ft long piece of roof supporting itself and 2x10 pieces? I just hear about roofing today utilizing either 2x10s or similarly strong pieces of lumber instead of the 2x4 rafters of yesteryear. Am I being too paranoid? I think the angle of the roof is near 45deg if that matters and like is said, the roof and ceiling will run unsupported except at the ridge board, the top cross tie (approx 4ft in length), and the top of the exterior wall, where it also meets the floor joists/ceiling ties.