Hi all,
I have two layers of sub floor. 3/4" ply over 1/2" ply. The top 3/4" layer of ply has gaps between the sheets and some of the gaps are as wide as 1/4". I will be installing 3/4" 3 1/4" cherry on them. Do I need to and how could I close these gaps in the subfloor? Replacing the sheets would be hard as I made end up having to replace more than 300 sft of them.

thank you for your help.

¼", Your good to go as long as one side isn't raised more then the other, wespecially along the lengths of your finished flooring.