[Teats]

I was going to put a deck out side my sliding glass door of my room, which is on the 2nd story of my house. I wanted to replace the old header board. Once I removed the header board, I saw that the wood under neith was rotten. I then started to proceed removing the vynal siding and the old hard board siding and found that pretty much the entire outside "bones" of the house where rotten. My house was built in 1984, with no OSB board put on. How do I fix this without the entire 2nd story falling?

[21boat]

The first thing to do here is have a professional come out and check for termites.

Next thing if its not termites is check for water leaks from the roof and all openings Windows etc.

How do I fix this without the entire 2nd story falling?

To help answer that question you need to remove enough or all of the vinyl siding ans see if the bottom stud plates are good and the top double plates condition.

Once its determined that they are good you can remove the old fiberboard and start replacing studs.

At this point get the exterminator out and check for leaks and get back. If there's structural damage then more may be involved here. Also check your Homeowners insurance policy and see what that coves.