I am in the process of re-flooring a 500 sq/ft area of my home with prefinished 3/4" oak. Most of the sub-floor is plywood, however, there is a small section of about 100 sq/ft of this area that has an unconventional sub-floor. It is 1.5" pine plank, about 100+ years old laid perpendicular to the joists, with 1/4" luaun over it to bridge any gaps and cupping and bring it level with the other 2 layers of ply in the rest of the room.
If I were to lay hardwood over this section it would be parallel to the existing plank sub-floor section. I know this is theoretically a no-no, but would that cause problems, or would the old wood be now stabile enough to be a non-issue?
Just a side-note: It registers an extremely low level of humidity on a meter (< 13%), and this is during the humid season in my home. Also, I do not want to remove it as it is integrated under the bottom plate of exterior walls and there are partitions over it. In essence, it would be a surgical operation.
Any thoughts on if this is ok to floor over? This section of the room is about 10' wide and I'm using 3 1/4" oak t&g, so the expansion is about 1/64" each piece tops. I'm guessing worst case still might not be too bad.