We removed travertine tile from the kitchen to extend hardwood floors through out the house. Underneath the travertine was plywood on top of the 1x6s. Can we also remove the plywood and lay the hardwoods directly on the subfloor? I'd like to avoid transitions and different levels between the rooms.
Was the plywood and 1x6 both on top of the subfloor? If this is the case and the subfloor is solid and at least 3/4" I don't see why not. Just make sure to resecure and replace any damaged areas cause this can cause squeaking and affect the performance of the finished product. Remember to let the wood acclimate 4 to 7 days before installing. Use a moisture barrier and leave the proper expansion gap around perimeter and fixed objects.