How big a gap between floorboard/plywood will underlay hide?

[garviel]

Hi everybody,

I have just had my old floorboard subfloor replaced with plywood. between the plywood sheets there are still gaps ranging from 3mm to 10mm. I plan to lay underlay (10mm tredair or like) and then carpet (hessien backed).

My question is, how big a gap between the plywood sheets will the underlay hide?

Thank you, Garv

 

[Burnerman]

3mm is fine, but 10mm is too much. If you don't see any depression immediately, you will in time! I guess it really depends on the thickness of the carpet.
John