I'm going to install 3/4" solid red oak hardwood upstairs, but the subfloor is old, creaky, and needs to be replaced. The floor joists are spaced 24" OC (on center), and change direction in the middle of the room.
From what I have read, if I want to run wood flooring parallel to the joists, 24" OC is not sufficient, but what I'm not sure of is if I add additional bracing perpendicular to the existing joists, can I add the bracing at 24" OC, or should I add it 16" OC? In other words, will having a grid of 24" squares to support the OSB work, or should it be 24"x16" rectangles? Obviously 16" OC is 50% more expensive and time consuming.
I'm going to be laying down new, premium 3/4" OSB subfloor and then laying the oak flooring on top of that. I don't have the budget for plywood, and anything thicker than 3/4" subfloor will also not work.
I plan on laying the OSB with the 8' sides going top to bottom, and the finished floor will be laid running left to right. Direction of OSB is negotiable.
Floor joist drawing: