Since buying this house in 2016,  I knew that the source of the water damage was the failed flat roof on the addition above the kitchen.   I knew it leaked bad, and I knew it leaked for a long time. 

    What I did not know for sure, but strongly suspected, was that the water was also running down around the outside of the chimney on the back wall of the kitchen.  The demo two weeks ago confirmed this.  Water had been pouring down the outside of the chimney because there was no roof slope  or flashing to divert it away or around the chimney.

The water not only rotted/destroyed the kitchen floor and back wall, but it eroded the stone foundation and the timber that acted as a sill for the rear wall to be built on.  See this photo:

 
There was nothing left to start building off of.

Rob and I had to pour concrete around the chimney and create a place to attach a  2 x 8  pressure treated sill plate.  From there we were able to create a pressure treated "header" type beam or ledger board. This was made from two 2 X 8's  sandwiching a piece of 3/4" plywood.

Finally we were able to install more floor joists and start framing out the new rear wall and doorway.