Hi - I'm not an appraiser but working on a property valuation appeal. The issue is a detached storage shed that has electricity, otherwise unfinished with painted OSB. It has a loft, and is about 300 sqft. The issue is I'm fighting with the assessor, who insists this is a "guest cottage" (code 328), and should be valued at $30,000. It doesn't have heat, AC, or plumbing. It does have a sliding door and a few windows. My question is this: My state (by statute) prescribes the use of Marshall and Swift, and I've found numerous similar-sized storage sheds with electricity (mostly man-caves, wood shops, etc.), and they are all coded 1637 - wood storage unit, but none of the property cards assign a value to the external unit under that code. My argument is that it shouldn't matter what the building is used for, only the construction materials, etc. How do I find data that supports a comparable valuation of the shed/storage unit? Is there someplace online where I can find the Marshall and Swift calculators for this?
Every other "guest cottage" I've found is a pool house with plumbing, and in most cases heat and A/C. Thanks in advance.