plywood 9mm on cupped floorboards - for LVT click

Hi

Layed some 9mm ply on some cupped floorboards - the ply has followed the floorboards in areas and when I've put a straight edge across can see gaps of 1mm, up to a max of 3mm in one area. should note large area is nice and flat its just in the middle of the room where the floorboards are cupped.

Was intending on just ardex feather fisnihing the seams, but in the areas where there are 2-3mm gaps should I build this out with ardex feather or use a self leveling screed in these areas?

Intention will be to install Quickstep alpha vinyl plus click LVT.

THanks

 

The gaps won’t be a problem. The floor needs to be perfectly flat


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Sorry just re read. The gaps under the straight edge. Yes levelling compound needed


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what sort of self leveller should I use? does ply need priming prior to self levelling?

 

Ardex p51 primer on neat and ardex K40 HB

 

How best to apply the primer? Pour then roll on? Does it need to dry out before putting levelling compound on?

Presume levelling compound is mixed to creamy mortar consistency poured then levelled/floated over area?

THanks

 

Each product comes with quite easy to follow instructions ( unless you're a builder),as long as you follow them, you shouldn't go wrong

 

Thanks. Makes sense.

Just another final question - should I feather over screw holes? I've made sure screws are flush or just sunk below surface of ply.
I believe the quickstep LVT im planning to get needs a 1mm underlay before laying.