OSB overlay over chipboard subfloor

Folks,

Need to raise the level of a floor by 12mm and have a load of 11mm OSB to hand. Subfloor is 18mm chipboard screwed to joists

What's the best way to fix? Screws, nails, staples or glue and screw? What size screws/staples etc?

Does the OSB overlayment need to run at 90 degrees to the chipboard subfloor or in line with it (avoiding joints below obviously)

Cheers

 

90° is best. I’d go 25mm screws.

 

I’d screw down the 11mm OSB tight to the chipboard, then make up the missing millimetre with a thin leveling compound so the floor stays flat and solid.