This is what we had to deal with.
Most of the floor joist had rotted where they went into the stone wall. Partly due to termites but mostly due to moisture.
We cut out the most rotten of the wood, scabbed in some new pieces and sistered in new joist along side the existing. We then put in some new support beams and posts all the while raising and leveling the floor as best we could without disturbing too much upstairs. The floors had sagged a lot over the years. As much as 3" in some areas. Had it not been for all the makeshift supports it may have been even worse.
I found this little guy who wasn't so lucky. I found him inside one of the main beams.
Looks like he has been here a while.
A closeup of some rotten wood that I thought was pretty cool.
Next came replacing the joist in front of the fireplace over the arch ways.
A little cement work was needed.
In goes the new joist. Good as new.
All this fun lasted about 3 weeks with a few breaks in between. I am a few weeks behind in my time line but I am catching up.