When I started to frame the fireplace opening in the floor I found some fairly significant rot.
I built a series of temporary walls inside the house to support the weight that would normally rest on the sill and today started demolition. I’ll pour a concrete cap on the old foundation and put new floor joists on top of that cap. Then take out the temporary walls.
I did the west wall, roughly 30 ft long, today. Tomorrow I'll start on the north and south walls, at 20 ft each. A total of 70 ft.
I've worked on a number of old houses and never seen the masonry piled up in between the joists like it is here. That accounts for part of the rot; all that masonry wicking moisture right next to wood. On the other hand the building has lasted for 100 years.