I have now added lots more 2 1/2" screws, at least 3 per 600mm wide board in every joist and screwed them well home, and it has helped greatly to the point of being able to live with it.
I think I will also try the talcon powder method; I've heard this idea from a few different sources but...
I have now replaced most of the existing 1 1/2" screws with 2 1/2" x no10 screws which has helped but not cured the problem. I have now decided to change all the screws with the larger size.
Fairly sure that its the joints between the boards that are creaking and not the joists. It also...
I have a loft extension with a creaking T&G chipboard floor. I have screwed the boards down to the joists using God knows how many screws but they are still noisy which is driving us mad.
I am now thinking of srewing down 12 mm plywood sheets on foam over the chipboard floor.
Can anyonw tell...