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It seems laminate plank or vinyl plank flooring is becoming overly popular. Ranging from $1.50 a square foot up to over $6 a square foot it sure is a wide range. I'm seeing the higher end floors come with padding on the bottom already glued by the factory. They claim no padded underlayment is needed that way. But in new construction the typical subfloor is just 3/4" OSB.

I don't see the osb with cracks and defects being a good subfloor choice. Would simply using 1/4" 4' x 8' sheets of underlayment be a sufficient base for these new plank floors? I assume less detail would be needed such as not needing to putty the seams and staple holes in the underlayment. I like that it would raise the plank more to be level with any carpet or tile transitions. But I'm wondering what you guys have used for a solid base layer before installing these floating snap and lock laminate or vinyl planks?

  • Cracks and defects? Do you mean joints and texture? OSB is supremely stable (more so than plywood, barring flood conditions), and small (<1/8") texture has no bearing on how well it supports flooring. The primary concern would be flex, and that's mostly a matter of opinion, as this type of flooring isn't prone to cracking. 1/4" underlayment adds very little stiffness and is usually a surface preparation for sheet vinyl, so I don't see it doing much in this case. – isherwood Dec 9 '19 at 13:51
  • I will say that at the home store, there is a grade of 1/4" plywood that is sold specifically for underlayment. I had to put vinyl plank in a room adjacent to some ceramic tile, and it was great to smooth out the floor and raise the level... That said, i'm not sure how much it's needed in your specific case. – JPhi1618 Dec 9 '19 at 15:39
  • Not needed, but it can add insulation against temps and, more importantly, sound. you don't want to staple or otherwise attach it, it should float just like the flooring. – dandavis Dec 9 '19 at 22:12
  • @isherwood, yes, and blisters from rains, couple defects in sheets, and in general whatever damage comes from construction and rain. The other thing is that laying plank flooring right on the osb seems to me that the plank would be super short at any transition. And does it float very well on OSB? Specifically the newer kinds that have their own padding on the bottom? – Nic Dec 11 '19 at 13:50
  • As a general contractor I would rent a floor sander if the OSB was damaged as you describe. In fact, since we get regular rain and resulting swollen joints, it was routine. Otherwise, there's no concern. – isherwood Dec 11 '19 at 13:52

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