Squeak free plywood subfloor

[SimonD]

2 hours ago, faby said:

interested in views on appropriate size of expansion gap between boards.

 

3-4mm all round should be fine.

 

When choosing your glue, as mentioned use a D4 but do make sure it's of the polyurethane type that has some natural expansion as this will fill small gaps and voids - as advised by @MikeSharp01

[MikeSharp01]

1 hour ago, SimonD said:

taxonomy

Cripes! I think that pin head just got smaller or alternatively we have all gone slightly NUTS.

[PeterW]

@faby get some decent 4x2 (CLS will do) and run it down the side of every joist that you have to adjust the height on and glue and screw it on the side. It will both give stiffness and a wider landing for the ply joints. D4 glue every joint - you need 2mm max between boards but try and land all joints on noggins. If you have access from below then even better - lay the boards then glue a 4x2 on flat below each joint and make sure it’s tight to the bottom of the boards. 
 

What is your final floor finish going to be ..? And I am assuming you’re also using decent sound / heat insulation under the ply in the void too..??