Re: Hardwood floor over concrete ( not basement)
I would use a floating floor system. Floating floors do not attach to the substrate, hence the term "floating'. Typical installation of a floating floor over slab is to lay down 6mil plastic sheeting with seams having a 3' overlap and fully taped, 1/8" foam pad with fully taped seams, then the flooring. Be sure to leave a 1/4" gap around the perimeter for expansion. Baseboard or base shoe will cover the gap.
If the concrete is rough or uneven, then I would smooth it with thinset or floor leveling compound before laying the plastic.
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