I'm remodelling an 1882 summer kitchen which is attached to the back of my house. The addition is actually two rooms. I'm insulating and drywalling the room which is attached to the main house (so it is "sandwiched" between the main house and the second room of the summer kitchen). The room I'm doing had interior 1x8 sheathing, no insulation, then rosin paper and cedar siding nailed to the outside of the 2x4 studs. I'm planning on using bat insulation with paper to the inside and drywalling over. My question is, do I need to put plywood sheathing over the inside of the studs before drywalling? The two exterior walls (east and west) of the room are about 12' long and 8' high and buttressed between the sheathed back room and the main house. Are the 12' wide x 8' high walls strong enough to avoid racking without sheathing or diagonal bracing? There is a small unused loft above both summer kitchen rooms with a steeply pitched roof above. The roof rests directly on the east and west exterior walls of the summer kitchen. The gable ends are attached to the house on the south end and freestanding on the north end of the uninsulated room. Also, the original rosin paper is deteriorating in places. Would it be good or bad practice to put roofing felt on the back side of the cedar siding--noting that it could only be installed between the studs and not over them? Would that allow the new insulation to breathe? Should I leave the old rosin paper in place before insulating? I hope my descriptions of the situation are not too confusing. Thanks!