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I had an addition built over my existing garage. I only farmed out the shell, i.e. framing, sheathing/subfloor, siding, windows and roof. I'm doing the rest myself. The space is 10'-6" x 25'-0".

The contractor used 2x10's for the joists. The subfloor is 5/8 (actauly 19/32) plywood (not tongue & groove), and nailed down with regular framing nails (not twisted nails or ring shanks) and no PL.

I now know what could have or should have been done, but that is water under the bridge, and I need to make the most with what I have. The plywood subfloor was run with the long sides running along the 25' side and the joists span the 10'-6" , so the 4' edges of the plywood sheets butt up on joists, but the long continuous joints run the full 25' length , which occurs in two spots ( one between the 2 full courses of 4x8 and one between a full course of 4x8 and the course of 2'-6"x8' ).

Finally, there is no bridging. The subfloor feels sort of "soft" and squeaks at some of the unsupported plywood joints.
I experimented in one third of the space and sort of "caulked" PL from underneath into the joint between the joists and the subfloor and then screwed 2" deck screws down through the subfloor into the joists at about every 8". I also ripped 2x4's the width of the joist bays, PL-ed the tops, nailed them into the joists tight to the underside of the subfloor at the unsupported joint between the plywood sheets, and then screwed the subfloor down to the 2x4's.

The subfloor definitely feels nice and solid now, and I am not worried about any future floor squeaks in that area.

Here are my questions:
1) Is it overkill to put the 2x4 supports in - even though it squeaks now, maybe it won't when the finished wood flooring is put down.

2) I was going to nail and PL in full 2x10 bridging down the middle of the space (running down the middle of the 25' length, basically 5'-3" on either side of the bridging). If you say that the 2x4's are a good idea, it seems that they would actually act as small bridges, but they occur more frequently (there would be 4' on either side of one set and the other set would have 4' on one side and 2'-6" on the other side) so would I be wasting my time also putting in the full bridging down the middle?

Sorry for the length of this posting for such short questions but I wanted you to have a complete picture.
Any suggestions or advice would be greatly appreciated.
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