To ply or not to ply?

[Dr.SteelHammer]

Hi guys,

Looking for some advice as I'm new to laying flooring. I'm hoping to install some engineered wooden floor in a first floor bedroom, I have ripped up the carpets and exposed the subfloor which are old floorboards. These seem to be in average nick and fairly level (the odd one or two are slightly cupped and have gaps between but these are ones which were replaced by the plumber and done rather shoddily at that).

My question is: if I screw down any loose floorboards, replace the crap ones and sand down the odd one that's not quite level can lay 6mm fibre board on them and then lay the floor in the same direction as the old floorboards? The reason I ask is I have seen lots of advice saying if you are laying onto old floorboards directly you should lay perpendicular to the old floor otherwise you can getting a uneven/wavy engineered floor.

If the old floor isn't perfectly level will the fibre board resolve this or would they over time sink/mould to the imperfections and dips of the old floor? Or would i be better just leveling with plyboard? The engineered floor is 14mm thick so is I was to use ply what thickness would I need to use?

Any help would be greatly appreciated. Thanks.

 

[Dr.SteelHammer]

Bump?

 

[foxhole]

Ideally cross board existing running towards windows, if you want to run inline then overboard with 12mm ply , screwed every 300mm.

 

[Dr.SteelHammer]

Thanks foxhole. The old floorboards run toward the window already unfortunately. That's the direction I want my new floor to run so can't crossboard . I guess it's ply board for me then.

 

[crazydaze]

If you float the Engineered you should be ok, if you are floating and at all concerned, 4mm Hardboard would suffice or 6mm ply if you want to be super fussy. If you are fixing to the subfloor, you have to use 6mm Ply.