Unusual Floor Joist Connection

The floor joists above the crawlspace were set several inches above the sill plate, resting on short vertical 2x4’s. No joist hangers or obvious toe nailing to the rim joist. Also note the “support posts” in the photo. Has anyone seen joists set like these?

Yes, that method was often used to line up floors of an addition when the foundation wall tops varied.

They need some attention.

Cripple wall code info I didn’t check all references but it’s a start

“Non-professional carpentry”. Good work would have required them to build a short wall (“knee wall, pony wall, stub wall” different names all mean the same thing.
Call any sign of failure.

Carpenter Ant Frass present in photos 1-3

Did anyone probe that area?

There may be or has been a leak here. Moisture stains on the underside of the subfloor and the end of the joist. Wood destroying Insects are attracted to soft spots like this. You don’t need to identify the species, call it out and recommend a pest inspection in that area.
As for structural integrity of the joist and sill area, it has stood the test of time so simply “unconventional construction”, IMO.
The last picture with the props looks like amateur retrofit and requires a repair by a qualified builder.

John Kogel

How old is that building?

Home was constructed in 1942, this crawlspace appears to be a later addition. The original home was built over a full basement. Water stains were old, the kitchen above was completely rebuilt. Actually did not find any significant soft areas by probing.