Originally Posted by joecaption
Sounds pretty normal for an older house where the DIY home owners wanted to "save time" and just keep adding on to the top layer.
One of the many reasons most of us here suggest not doing that.
The real killer is the absence of foundation under this area. I've mentioned before in my description of the house, but the original 22x24 was built in 1917 then another 10' was added to the back. That's what the kitchen is in. This 10' addition is held up by concrete blocks under the joists, and these sit on dirt. They've sunk more than the rest of the concrete blocks. I think the sinking might have stopped when the next addition was put on, a 10x10 mud room was added which is on a proper concrete slab.
What complicates the story is that because of this brick addition, I would have a harder time jacking up the balloon framed addition, so instead I'll have to replace floor joists and cut off the bottom of wall studs and put in a new bottom plate underneath. When I get to the second floor, I'm thinking there will be new double top plates on all existing exterior walls.