I’m having a new ¾” maple hardwood floor installed over my existing maple hardwood floors in my unit of a 1925 condo building. The existing floor assembly is:

joist @ 16”on center
¾” plank subfloor
1” sleepers (aligned w/ joists)
¾” Maple floor

If I bounce on one foot on my existing floor on the span between the sleepers, there is noticeable movement in the floor. The flooring installer is cautioning that the new floor must be installed perpendicular to the existing maple finished floor, which would be parallel to the sleepers and joists. This rule I understand is so the seasonal moisture / thermal movement of the two floors doesn’t work together to exaggerate gaps in the new floor. But I’m wondering if running the new floor w/ the existing floor is better for stiffness given the sleepers / joists direction.

I should add that before the new floor goes in I am planning on screwing off the existing floor frequently (6” OC) along the sleepers / joists to tackle some of the squeak that is in this old floor.

Any thoughts / comments appreciated.
Thanks!

Never go the same direction as the old floor when installing over.

Thanks for the response.
Can you elaborate why not?

Because it may panelize, meaning the flooring will move with the old underneath causing gaps. I've seen it happen, I've warned people yet they got some flooring guy to do it the way they wanted.