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Doggit
There's been a lot of questions over some of the luxury vinyl planks, but if you're going down onto ply, you should be alright; but they hate any imperfections whatsoever in the floor. Your leveling screed is more likely to be self leveling compound, but as I always warn people, they never level as well as they should, and they need careful handling, so make sure the builders have used them before, and ask just how level they are able to get it.