The house’s HVAC system relies on large floor air returns.
One return is squarely in front of the right panel of the new french patio door. It’s too early to completely cover and remove the air return, but some repair work on the subfloor will be needed for the door installation. And it will be much easier to do a bit of prep work at the same time.
The subfloor is 3/4″ shiplap boards, and under the planned door location it is broken and cut back rather carelessly. This will need to be repaired to give the door solid support, probably by replacing a section with plywood. I want to be prepared for the future addition of a subfloor where the current hole for the decorative grate is located.
The grate rests on cleats attached to the floor joists; the future subfloor should rest on the joists and not these cleats.
I’m thinking that a cut should be made centered on top of and parallel to the floor joists, cutting through the finished floor and subfloor. This cut will allow us to remove the flooring exposing half the top of the joists, the support for the future subfloor.