ADU Appraisal Value in San Diego

[Peter Amador]

I am building an ADU on one of my rental properties and looking to maximize the appraisal value. The ADU will not be attached to the primary home and will have a separate entrance with parking.

How have appraisers been valuing stand-alone properties? For example, if comps for the primary home are $500 sq ft, are ADUs in the San Diego market being valued at $250 sq ft? I believe a duplex comp is most appropriate but I am trying to get an estimation on what the appraisal could come back under worse case scenarios. Any insights shared about ADU appraisals would be greatly appreciated. Thanks!