[Scuba_Dave]

Instead of concrete pour a footer around the edge
Then build a framed floor & insulate it

Or pull the siding off in advance & add baseboard trim once the sunroom is completed
I made my sunroom floor even with the room inside
I then put in LVL beams & opened the wall between the 2 rooms

 

[slowjo]

do not pour the concrete against the sill or house. Im dealing with that nightmare. The previous owner had done this and it destroyed the sill and, stud and joist ends. Concrete should not contact the wood in that manner. I would do as previously suggested. Frame a new floor ontop of a pad or footing.

 

[Gary in WA]

They have a membrane (nervestrave)s.p., that will protect the wood. But, you will add about 16-20 yards of fill plus the slab, judging by the fall of ground. Plus a foundation. That's a lot of work. For a foundation with crawl space, you'll need to pullout about 18" under the floor joists from top of mud sill down. You're almost there. Much easier, I think. Course, all is naught, till you get your permit. Be safe, G

 

[Maintenance 6]

On top of all the above, your grade to the right of the door is already way too close to the wood framing. The finish grade should be at least 8" away from the wooden parts of your house. More is better.