As mentioned, put noggins everywhere. This will stabilise the whole lot.I replaced all the boards with 22mm chipboard and there is basically no improvement... I didn't bother gluing down as I could tell the floorboards are not the issue, the joists are the things that are creaking. Standing on the joists directly with no boards still creaked. Could I try sistering the joists perhaps?
Literally, 3x2s cut individually for every location, to the mm and screwed with 4no. 5x70mm screws per noggin.
