This makes a lot of sense. Previously, there actually was no blocking supporting the king and jack studs of the door because the blocking was outside of the plane of the wall. The 2nd floor subfloor and bottom plate were sagging as a result. I was blown away that the builders did not use proper support.The blocking should be double thick under the sides of the door to support the king and jack studs for the door.
To install the blocking, would you recommend toe nailing them to the joists, or is there some other method?
Do you have a recommendation on how many? Eg. One for every 15ft of ledger?You should add some tie backs too.