I'm in the process of converting my attic into a bonus room, but I've hit a snag with the joists. Some areas are missing flooring, and I'm noticing that the joists aren't uniformly spaced or are twisted. For instance, the first board I tried to lay down is aligned on one end over a joist, but the other end is almost off the joist entirely, leaving half the board unsupported. I've heard it's tricky to adjust the joists, but I think if they're just twisted, I could nudge them enough to fit blocking. Should I support these areas and leave the joists as they are, or would it be better to trim the plywood ends to match the joist layout more closely?
2 Answers
Your best bet is to sister the joists to make them more level. You'll need to buy some 2x6 or 2x10 boards and attach them alongside the existing joists. This makes everything more uniform and gives you a solid base for your subfloor. Just remember, back in the day, they often used random scraps for framing, so it’s not unusual to find inconsistencies.
If you can get access, sistering the joists on both corners of your panels can add a good 3 inches or more. Just make sure everything is level before laying down the subfloor, so you have solid anchoring points. It should give you a stable area to work with for your bonus room.
So just to clarify, you mean put sister boards only under the corners of the panels, right? That way I'll have something solid to screw into?