Hello, I recently gutted a large room where the plaster was in bad shape and the there was no insulation in the exterior walls. The room above this one has a decent amount of bound in the floor and when I open the ceiling in the large room I found that whoever put up this addition framed the ceiling with some 2x6's, some 2x8's and even 1 2x10. They used blocking on the top plate to level the floor above. The height of the bay or from the floor above to the first floor top plate is 10 1/4 inches. I was just going to sister up the joists, cutting the blocking flush with the existing joists, resting the new 2x10's on the top plate of the first floor and gluing and screwing to the existing joists. The joist are running the width of the room and the room is 14.5 feet wide so I believe the 2x10 should be enough to help with the bounce issue on the second floor.
Two issues I have are the blocking on the interior wall and the way the existing joists are connected to the 2x4's in the wall. The interior wall is balloon and they nailed 2x4's on the flat between the bays that the joists rests on, I am not sure how I feel about this and I am hoping for some advice at to the best way to improve this. The second issue is most of the joist are sitting against the 2x4's in the wall but if the 2x4 is on the left side of the joist on the exterior wall it is on the right side of the joist on the interior so I cannot rest the new 2x10 on the top plate on both sides. I hope I wrote this clearly and any advice would be appreciated, thanks.
I finally devised a plan, i've decided to sister up the existing studs. I am going to cut the blocking under the existing joists flush so that I can butt the new joists right againsts the old one. Glue and screw the new 2 x 10's to the existing joists. I am also going to build a new wall in front of the the interior wall that is bloon framed so that the new joists will rest on that. I will lose a little interior space but it was the best plan I could come up with. I will post pictures when I am done.