Unevenness and leveling methods

Q: I’ve got a 30 year old 2nd floor condo with a cement floor. We’re planning to install walnut floors over 900 sq ft. When we took up the carpet, we discovered that in some areas the cement is uneven. We’ve got three quotes from installers, but each uses a very different method.

One says to lay down a whole new cement sub-floor (for $4k), then nail plywood into the new sub-floor and the hardwood on top. One says to float 5/8″ plywood one way and 3/8″ plywood the other way, then nail the walnut in. And one says to simply use a self-leveling┬ácompound in the uneven areas, then screw-in 3/4″ plywood, then lay the hardwood.

It’s a lot of money, so I want to pick the approach that’s right. Which route would you suggest? And have you got any ballpark thoughts on what this should cost me?

A: Provided the unevenness is not severe, I would install Mirage engineered, glue down installation. Forget about the plywood. Mirage engineered has a top wear surface near equal to that of a 3/4 thick floor and can be sanded if needed, about as many times as a solid wood product. So why go into all this extra expense?