On May 5, 9:01*pm, Red Green wrote:
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?

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