Plank sub-floor

[pburchett]

Installing a hardwood floor on a plank subfloor.

The plank sub-floor runs perpendicular to the 2x10 floor joist, on 16”centers.
We do not want to add another layer of plywood or whatever to the plank sub-floor so that the floors throughout the house are the same height.

We are going to have a contractor install the 4 inch, pre-finished, red oak flooring, but can not decide which contractor is using the best method.

The floor is over a basement, and I have sanded the sub-floor flat with a drum sander, so all is level.

The living room is 34’ wide x 28’ long which connects to a hall 28’ long and 4’ wide.

Contractor 1 wants to install the flooring parallel with the joist, which would be laid across the planks. We are afraid the plank sub-floor will sag and leave a wave appearance in the floor between the joist.

Contractor 2 wants to install a ¼” sheet of luan over the sub-floor, then run the hardwood flooring the entire 56’ length of the living room and hall. This contractor is my choice, but I wonder if the plank sub-floor was to ever cup would it transmit through the luan and cause the hardwood to distort? If we go with this contractor, would ¼” plywood be better than the luan?

Thanks in advance for any advice.

[Floorguy]

The rule when there is existing strip or plank flooring, is to lay across it in the opposite direction. Adding 3/8" plywood minimum to the plank slats, makes it stable enough so you can run the flooring in any direction.