Flooring question: New over old?

[Van Huskey]

I would not lay it perpendicular to the old floor, because you really do want the floor to be perpendicular to the floor joists. Even if you think the existing floor is dead flat, the floor tends to move 1 joist at a time when you walk across it, and you want that movement to be resisted by the grain direction of the floor.

To picture what I am saying, think about a two pieces of t/g flooring fit together. If you try to flex this assembly across the grain, it will easily flex at the joint. If you try to flex it the other way, it will resist.

That is a retty old school view today...BUT it appears to be a pretty old school house so it makes great sense. In the end I would REALLY prefer an inderlayment to tie the whole thing together it would make for a better floor in so many ways.

[guy knight]

That is a retty old school view today...BUT it appears to be a pretty old school house so it makes great sense. In the end I would REALLY prefer an inderlayment to tie the whole thing together it would make for a better floor in so many ways.

if you did want to lay it in the same direction with the joist i would use 1/2 cdx then you would be fine