While removing layers of flooring in the kitchen of my 1912 house I got down to the final layer which is cement backer board which they nailed down no screwed were used. The floor is not level at all. I am laying down a floating laminate floor. Do I need to remove the cement backer board & lay down new wood subfloor or can I use a self leveling compound over the backer board then an underlayment prior to putting the new floating floor down?