My house is about 50 y.o. I have top nailed, 2", oak floors in the 1st floor that squeak a lot. Several years ago, before putting in new oak floor in the front hallway. I screwed the tongue and groove, 4" subfloor to the floor joists before glueing and top nailing the new oak floor. This worked great, there are no squeaks on this new floor, yet. Is there a way to stop squeaks across the rest of the floor. The floor is open underneath, there is a crawl space. I thought about a good glue (If this might work, please, suggest a glue) along the entire length of the joist and into the joints between the subfloor. Or, screw a 1" x 1" along the joist and then lag screwing in to the subfloor. I am worried I will not get enough purchase to hold without going through the floor above. Any suggestions appreciated.