the real world is funny sometimes. i am a great example.
in 2013 i bought a house via an estate sale that had not been updated in 30+ years with a few exceptions - windows were 4 years old, roof was 10 years old. i completely gutted the entire house down to studs. put in all new electric (including 3 panels, removed all the knob and tube), all new pex plumbing, all new drywall throughout including ceilings, new kitchen, new baths, new flooring, new water tank, new furnace and ca, new sump, finished 70% of the basement, new siding, new temp/humidty controlled exhaust fan in the attic, rebuilt the chimney and added a new liner and probably more that isn't coming to mind. in a nutshell everything but the studs and the foundation were replaced.
refi'd and the appraiser called it a C3. granted i am impartial as it's my house AND i am an appraiser but i would have thought it to be a C2. to be honest i'm not sure what more i could have done in the appraiser's eye to make it a C2 - there wasn't anything left to do.