Appraisal + refi before or after *unpermitted* "casita"

[Brent Blum]

Who is right, my GC or my agent?...

My wife and I are finishing the conversion of a SFH into a duplex in San Diego - primary residence on one side, rental unit on the other. We've passed final inspection and will be looking to do a cash-out refi ASAP.

The last part of the renovation will be to build an unpermitted 12x10 "casita" with bathroom in the back yard.  See the image below.  If we build the casita now and then refi, my contractor thinks the appraiser is likely to notice the casita is unpermitted and add $0 or possible subtract from the value.  My agent thinks it will add $0 or possibly add something close to the value of 120 permitted sqft, w/ bathroom.

Any appraisers out there?  Who is right, my GC or my realtor?  Should we add the casita before or after the refi?

Thanks!

PS - Anyone who can do a competitive cash-out jumbo loan, please feel free to reach out.