Thermal expansion: installing a hardwood floor and subfloor
Upon further research, it was made clear that humidity/temperature need to be stabilized first, temperature excursion would damage a hardwood floor.
After the temperature excursion is addressed through proper heating and cooling, the primary concern for expansion is against the walls, where a 1/2&quot; perimeter is to be left for expansion. If the Drywall is floating above the floor, the hardwood and subfloor can expand under it as needed.
The 8x4 boards of subfloor should be laid down orthogonally to the direction of the rafters.