Uneven Subfloor Joint

Have a hall where there is unevenness under carpet down part of the length. There will be new carpet going down eventually. Found that the subfloor has a joint that is not on a joist. About an inch away. T&G but it's obviously been ignored many years. Tongue is broken in some areas.
I plan to put some 2x' from underneath with the face across the joint and screw the subfloor to it from the top to get the two sides even (I hope). Then support that 2x with a 2x that is sistered to that nearby joist. Hoping I can get it pretty even but being in such a conspicuous place, I think ideally a piece of say luan should go over the floor before the pad and carpet go down.
This would be fine except that the hallway runs open into the LR area. Wherever that luan ends a new unevenness is gonna be created I believe.
Maybe I am overthinking this and once I fasten both sides of the joint solid, the pad and carpet will consume any slight offset.
Opinions and/or ideas?
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On Mon 05 May 2008 09:01:02p, Red Green told us...

I think you're overthinking this and your proposed solution should work, minus the luan.
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Wayne Boatwright
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RG-
I would suggest sistering with a 3x4 (2.5 x 3.5) or even just a full dimensional 2x4 or 2x6. If the joint is really only 1" off the joist, then 2" of wood should plenty (even 1.5" would be enough if you angle the screws)
Forget the luan, sister with a decent width member (doesn't need to be continuous, could be reasonably long pieces), screw the plywood down & belt sand out any mismatch.
You really just have an unblocked plywood edge, so you really don't need the "sistering behavior", just a diaphragm block), you could use 3/4" plywood (a full joist bay width) as blocking instead. Very lightly brad nail the plywood in place & then install screws from above.
cheers Bob
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I don't think I'm gonna need the luan either since it's padding and carpet over. Just playing "what if". I know as long as I get it solid I can always bring out the belt and orbital sander with a low grit.
Thinking afterwards, if I did need the luan, where it ends I could sand and/or use the flooring pothole filler to taper out.
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Once you get your 2x in there and get it supported, then take the belt sander to finish off any unevenness. A pad and carpet is very forgiving. You should be ok without the underlayment.
s

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Yep...part of the plan.
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